report Strategies for a High Comfort, Low Energy Retrofit in NYC Pursuing Passive

October 2018

Pursuing Passive Section be-exchange.org 1 report sections

4 Executive Summary

8 The Building

10 Policy Context

13 Passive House & EnerPHit

17 Retrofit Criteria

18 Retrofit Strategies

38 Retrofit Phasing

40 Benefits & Costs

45 Conclusions

48 Acknowledgments

Pursuing Passive be-exchange.org 3 executive summary

Improving the performance innovation. Extensive, holistic of buildings must be a central renovation of occupied buildings component of any response to is expensive and disruptive for the challenges of climate change. the occupants, and since such This is both an imperative and work is rarely undertaken there an opportunity. Responding to is no natural market to exploit. climate change by aggressively The diversity of our building improving the performance stock (in size, age, construction, of the built environment will etc.) further complicates matters produce buildings that are by making it difficult to scale superior in virtually every solutions—there is no one size capacity, and focus attention fits all approach. There are on an industry whose processes many resources that describe have lagged behind those of generalized solutions for building other sectors. types, but building owners will It is imperative to draw down require strategies more specific the energy use of buildings to their particular building worldwide to ensure an equitable before studying the feasibility of and sustainable future. Buildings a deep retrofit. With this in mind, contribute 40% of global carbon we have selected an existing emissions and an astonishing high-rise multifamily building in 70% in New York City alone1. New York City that represents a New York City estimates that common building type and will carbon emissions of the building serve as the case study for sector need to be reduced by this report. 60% in order to meet our current The subject building is climate action goals2. This will 15-stories tall, 123,000 gross require not only increasing square feet, and includes 163 the stringency of our energy apartments. Having carefully codes for new construction, but selected a building with both introducing a radical expansion features and challenges common of existing building retrofits, a to a broad range of buildings, sector notoriously resistant to we have applied the standard

4 be-exchange.org Pursuing Passive Executive Summary that we feel offers the most that most effectively meet the promising mix of reliability and requirements of EnerPHit and effectiveness: Passive House. describes ways to phase these Passive House distinguishes in over time while the building is itself from other standards occupied. We identify the most and guidelines by focusing on important technical and market occupant comfort and truly challenges of pursuing a deep reliable heating and cooling retrofit, as well as the significant energy savings, producing benefits and the costs. With high quality, cost effective each passing day, the urgency buildings ready for a future of with which we must draw down electrification, high utility costs our carbon emissions increases. and more frequent extreme We are entering a period in weather events. Passive House which incremental measures also includes a comprehensive that provide limited emissions standard explicitly for retrofits reductions might be insufficient of existing buildings, called in the long run. This report EnerPHit. explores feasible improvements The primary retrofit that will allow us to meet our components of achieving the climate action goals and, in the EnerPHit standard for our absence of relevant examples subject building are relatively of deep retrofits, provides high- simple: level guidance for the owners of similar buildings. • Replace the windows with Is it feasible? This study high performance units finds that retrofitting a high- • Reclad the façade with rise, freestanding residential insulation and an airtight layer building to the Passive House • Upgrade the ventilation to a standard presents very few balanced system with heat technical challenges and would recovery result in substantial benefits that • Replace the heating and would also require significant cooling with a high efficiency capital and extensive tenant system engagement to complete • Upgrade domestic hot water successfully. We find it possible and other systems to conduct such a holistic retrofit in several phases while the The study emphasizes building remains fully occupied, selecting those improvements but it is far less expensive and

Pursuing Passive Executive Summary be-exchange.org 5 far more effective in terms of strategies outlined in the report carbon emissions reductions to is $10.14 million, which equates perform the retrofit in a single to roughly $82 per square foot or phase. This report focuses on $62,000 per unit. We estimate the technical strategies required the total cost of business-as- to meet the requirements of the usual upgrades to the building EnerPHit standard and enjoy the would be roughly $3.64 million. significant benefits available. Subtracting these costs produces We have included cost estimates a net additional cost of $6.5 for the various measures, and million to achieve EnerPHit although deep financial analysis certification (which equates to is outside our purview, there is $53/sf, or $40,000/unit). Phasing clearly a pressing need for access the work adds a significant to capital to perform these premium of $1.6 million (due to critical upgrades. the additional general conditions To convince building owners and recurring setup costs), while to embark on costly and also delaying delivery of the full disruptive projects, we must benefits of the retrofit. These identify the clear benefits of figures are high, and we explore transforming their buildings— methods to reduce them, but which include comfort, health the costs of inaction across the and asset value in addition to building sector are far higher energy savings. Passive House and incremental approaches to has a demonstrated record of energy efficiency are unlikely delivering improved interior to meet our climate action comfort and air quality as well goals and may not improve the as reliable, consistent energy valuation of the building enough savings from heating and cooling to warrant the effort. systems. The deep retrofit In the pages that follow, described in this report delivers we outline strategies selected a far superior asset for both to minimize disruption to owner and occupant while also the occupants. However, the playing a central role in avoiding project would still require both climate catastrophe. equipment and finish work in The primary barriers every major room of the building, to embarking on such an including extensive work in extensive upgrade are capital the common areas and at the and disruption to tenants. The building exterior. While many total estimated cost of all the buildings perform efficiency

6 be-exchange.org Pursuing Passive Executive Summary Figure 1: The subject building faces many challenges common to a wide variety of New York City buildings, including masonry exterior walls with no insulation, aging windows and merely adequate ventilation. upgrades to individual systems, challenge faced by virtually there are limited examples every community is how to of occupied buildings that connect the individual costs perform the type of integrated of upgrading buildings to the retrofits delivering the level broader societal benefits of of greenhouse gas reductions avoiding climate catastrophe, as needed for most cities to meet well as developing strategies to their climate action goals. cope with those impacts we will Extensive, holistic upgrades to not be able to avoid. This report existing buildings can deliver outlines the retrofit strategies raw efficiency along with a high required for one building type quality living environment, and in New York City to meet the can enable a future powered by obligations imposed on us by the renewable energy along with specter of global climate change. resiliency in the face of future We hope this is the starting point climate fluctuations and crises. for a deep discussion about As Amory Lovins of the Rocky how we can deliver the benefits Mountain Institute has stated, outlined in the most efficient “The good news about climate ways possible, and how we can change is that it is cheaper to incentivize as many buildings as fix than it is to ignore.”3 The possible to undertake them.

Pursuing Passive Executive Summary be-exchange.org 7 the building

The project team selected an existing building with features and challenges common to many high-rise multifamily buildings in the region.

Figure 2: Typical Existing Floor Plan

Living Room Living Room Bed Room Living Room

Bed Room Living Room Bed Room Living Room Bed Room

Kitchen Kitchen Kitchen Bath Bath

Bath Kitchen Foyer Foyer Foyer F Kitchen Foyer Bath Elevator Bath

Bed Room Bed Room

Bath Bath B Foyer Foyer

Living Room Bath Living Room Bath Bath Bath Kitchen Kitchen Living Room Living Room Bed Room Bed Room Kitchen Kitchen Living Room Living Room Kitchen Kitchen

Dining Dining Dining Dining

Each of the 15 floors includes 11 apartments except the ground floor with 9. Apartments range in size from studios to two-bedroom units, gathered around a central corridor.

This study describes the New York City (as well as many feasibility of upgrading an existing other regions) and has many of the multifamily building in New York most common challenges that will City to meet the Passive House be encountered by anyone looking standard for retrofits. The building to perform a deep retrofit of an selected for study is a 15-story, occupied multifamily building. market-rate residential building on The owner of the property a small campus of nearly identical generously made drawings and buildings in Brooklyn. Constructed other information about the in 1950, the building has masonry building available but wished to exterior walls that enclose 163 remain unidentified in the report. apartments across 123,000 gross square feet. The tower is typical of a large swath of buildings in

8 be-exchange.org Pursuing Passive The Building Figure 3: Existing Building Systems Assessment

Elements Issues Elements Issues

Exterior walls Cooling No insulation Poor thermal performance Simple masonry. 4” face brick Window AC units, located in No air barrier Creates drafty conditions bonded to 6” concrete block. most major rooms Major thermal bridges at Major thermal bridge Plaster interior surface. perimeter floor beams Noisy, inefficient High long term maintenance costs

Windows Domestic Hot Water Little thermal resistance Heavy energy losses from Aluminum, double-hung Heat exchange at steam boiler High air leakage circulation loop frames (no thermal break), with constant recirculation Major comfort issues Requires running steam double-paned glazing with loop Condensation risk boiler in shoulder and small metal spacers Poor solar heat gain cooling seasons properties

Heating Ventilation Poor responsiveness No direct fresh air Two-pipe steam system Exhaust only at kitchens, Overheating common introduction served by duel-fuel boiler bathrooms and corridors. Each High short-term System is not balanced, in basement (serves 2 other type collects under the roof to maintenance costs drives infiltration from buildings.) Includes 25 riser meet at one fan. High replacement costs exterior and adjacent units pairs and simple radiators in Energy intensive each major room.

Figure 4: Existing Wall Section

Exg. Window

Plaster

Brick and masonry wall

Steam radiator

Finish floor

Concrete floor slab

Steel Perimeter beam Horizontal chase

The existing exterior walls contain no insulation, and the steel perimeter beams at each floor aggravate the situation, providing a clear pathway for heat to escape in winter, compromising comfort and encouraging interior condensation. The study proposes that the steam radiators be removed and most of the distribution piping abandoned. Figure 5: Like many buildings of this era, the window to wall ratio is low, in this case 21%.

Pursuing Passive The Building be-exchange.org 9 policy context

Our study connects the progressive goals of our City and State governments with specific strategies for an individual building.

New York City has addressed their annual energy and water the challenges posed by gobal use, and to undergo a whole climate change through a mixture building energy audit once every of long term planning and the ten years. The GGBP also required implementation of specific commercial spaces to submeter programs. As noted earlier, energy and upgrade their lighting buildings account for roughly 70% systems to current code, and of New York City’s total carbon established, for the very first emissions.4 Although a higher time, a building energy code for percentage than most US cities, the City of New York (with more nearly 40% of GHG emissions stringent standards than the New in the United States are from York State energy code).7 buildings; if US buildings were a In 2015, the City reaffirmed its country, they would be the fourth focus on buildings with the release largest global emitter of GHG of OneNYC. The current climate emissions, behind only China, the action commitments outlined rest of US emissions, and India.5 in OneNYC revolve around an As early as 2007, the City of aggressive goal of reducing New York identified buildings as citywide carbon emissions 80% a critical sector in their climate by 2050 (“80 x 50”), using 2005 as action plan, PlaNYC.6 This plan a baseline.8 This aggressive plan resulted in the development of envisions nearly all of the roughly the Greener, Greater Buildings one million buildings in New York Plan (GGBP, 2009) which required City undergoing energy efficiency large buildings to benchmark retrofits by 2050. The Mayor’s Office of Sustainability has committed City agencies to this effort, and the Administration and Figure 6: Total CO2 Emissions, by Country (2015) City Council have enacted new laws and implemented a series 10 of initiatives designed to plot the long-term road map for such reductions, including analysis 8 9,040,000 of pathways for both public and private buildings. A major component of the 6 City’s efforts is the New York City Retrofit Accelerator, a program connecting private sector 4 buildings with resources and advisory services to realize energy

emissions, million metric tons emissions, million metric 3,049,000 2 efficiency projects. The program 2 CO 2,066,000 1,948,000 includes a High Performance Retrofit Track to promote deeper retrofits of buildings than typical 1 China 2 US (less buildings) 3 India 4 US (buildings) (See NYC Retrofit Accelerator If US buildings were a country, their CO2 emissions would rank 4th in the world behind sidebar for more information). only China, the rest of US emissions, and India.5 Public sector efforts by the City also include the passage

10 be-exchange.org Pursuing Passive Policy Context Figure 7: NYC's Pathway to 80 x 50

2005 Baseline Citywide 60

50 2005 Baseline Buildings

40 16%

30 26%

20 42% 44% 60% From Buildings From 60% Citywide GHG Reduction 80%

10 GHG Emissions in Million Metric Tons CO2e Tons in Million Metric GHG Emissions 30% GHG reduction target from buildings 63% 80%

2010 2020 2025 2030 2040 2050

Citywide Emissions Building Emissions

To meet the 80 x 50 goal, the CO2 emissions of all NYC buildings must be reduced by more than 60%. The challenge moving forward is connecting this citywide goal to actions within individual buildings.2

of two 2016 laws that require in 2025. Legislation is pivoting Base Building in Context City projects meet LEED-Gold to focus directly on the building standards and be designed to use energy use, with bills currently In 2016, the City of New York no more than 50% of the median under consideration that would published the One City: Built to Last Technical Working Group Report9 energy use of similar buildings. limit fossil fuel use in existing outlining available pathways for Based on the benchmarking buildings relative to size and retrofitting NYC buildings to meet data compiled by the City, this occupancy type. If they become the “80 X 50” target set down by “low energy intensity building” law, the proposed mandates would Mayor De Blasio. This report divided target is the first of its kind in the take effect in 2030, impacting the buildings of the City into more than 20 typologies. The building country. These laws also mandate thousands of buildings across selected for this study fits within that the City develop a plan every borough of New York City. the “Multifamily, Post-war (to 1980), to ensure that capital projects New York State has also greater than 7 stories” typology, from 2030 forward use no more made significant commitments to which includes, in total, 322 million than 38 kBTU/sf/year (for new combating climate change. The square feet of building area, more than 5% of citywide building construction) or 42 kBTU/sf/ signature State level goal is an area and 15% of multifamily year (for renovations)- numbers 80% reduction by 2050, with an buildings. A rough estimate that match Passive House interim goal of a 40% reduction indicates that this segment houses requirements. in emissions by 2030 (baseline nearly 1 million people. These initiatives to improve of 1990). This plan includes an the energy performance of City aggressive efficiency milestone buildings are complemented by in 2025 that should keep the increasing the stringency of New State ahead of its original pace to York City energy codes in an drawdown emissions. The goals effort to drive the performance are supported by specific, heavily of new construction and major resourced programs like NY REV, renovations. Stretch codes which aims to radically transform were recently mandated for the generation and delivery the 2019 and 2022 code cycles, of electricity statewide, and transitioning to a code based on RetrofitNY, which seeks to create whole building energy use targets a market for holistic, rapidly

Pursuing Passive Policy Context be-exchange.org 11 State Wide Efficiency Focus About/Publications/New-Efficiency ventilation systems- and installing them New York State has also committed in just a few days. RetrofitNY hopes to The keystone of New York State energy significant resources to their RetrofitNY connect design and construction teams efficiency measures is a commitment program, designed to pair scalable, with large portfolios of buildings and to an 80% reduction in overall carbon holistic retrofit solutions with large provide assistance in the development of emissions by 2050 (and 40% by 2030). portfolios to create a volume market for repeatable, rapidly deployable solutions The State has recently made a further rapid building upgrades that approach tailored to the northeast market. As you will commitment to further reducing energy or exceed Passive House levels of see, the RetrofitNY program has particular use by 185 trillion BTUs by 2025, a 40% performance. Modeled on a European relevance to the findings of this report. improvement on the original 2030 program called ‘Energiesprong’ which target. This 2025 target is described in a industrialized the process of re-cladding Details available here: white paper titled New Efficiency: New small buildings with modular units that https://www.nyserda.ny.gov/All- York, available here: nyserda.ny.gov/ contained new heating, cooling and Programs/Programs/RetrofitNY

NYC Retrofit Accelerator deployable building retrofits. benefit from efficiency upgrades. The direction of City and State Reducing energy consumption The NYC Retrofit Accelerator policies are leading to a future saves money, but energy was created to accelerate energy efficiency retrofits in privately in which much energy use in efficiency projects compete for owned buildings. The program buildings is electrified, while other capital dollars with many other employs a team of “efficiency policies and programs are focused opportunities to increase the advisors” who assist building on greening grid energy sources value of a given asset. For an owners, managers and other and introducing the flexibility existing building, these dollars decision-makers in undertaking retrofit projects. Efficiency advisors required to support distributed are particularly scarce and might provide assistance with developing a generation. The findings of this be spent upgrading lobbies and scope of work, selecting contractors study will support City and State common spaces, or correcting to perform the work, identifying efforts while providing relevant maintenance issues. It can be financing and incentives, and building owners or managers difficult for energy efficiency verifying energy and water savings. The program includes a High with guidance on the feasibility of retrofits to compete with these Performance Retrofit Track (HPRT), transforming their asset to realize more immediately tangible designed to begin piloting the deep deeper energy conservation. improvements. The situation energy retrofit paths identified is exacerbated by the variable in the City’s Buildings Technical nature of retrofit projects. Working Group. The HPRT offers specialized assistance to building Market Challenges There is no simple answer to owners and decision-makers to the question: how much energy develop 10-15 year capital plans that The policy measures outlined will an efficiency retrofit save? sync retrofits with the building’s above are in place to overcome There are as many answers as capital replacement schedule. HPRT significant structural challenges there are projects, and decision projects are expected to achieve 40-60% reductions in energy savings in the market. Building owners makers often perceive this from a typical building. and managers routinely miss variation as risk. Additionally, opportunities for energy savings most efficiency projects are More information is online at: during major improvements of proposed as individual measures www.nyc.gov/retrofitaccelerator. systems. Many building owners (replacing a single piece of do not have long-term capital equipment or upgrading a single plans in place, and those who do system), making it difficult to rarely consider energy efficiency promote energy efficiency at projects. Decisions about major significant scale. equipment replacement tend This study provides guidance to occur during emergencies for a specific building type to when the most expedient encourage capital planning option is typically selected, with that supports deeper retrofits. limited regard for long-term Such plans have the potential to utility costs or other benefits of shift the expectations of energy high performance options. In efficiency retrofits from a burden some cases, mature real estate to an opportunity, encouraging organizations have capital building owners to remain planning in place, but even competitive as more and more these often do not mix capital efficient projects come on line and operating expense budgets, to meet our steadily progressive severely limiting their ability to energy codes.

12 be-exchange.org Pursuing Passive Policy Context passive house & enerPHit

Following the Passive House criteria for retrofits, called EnerPHit, ensures ensures a building with high quality interiors and low utility bills.

Passive House • Highly efficient mechanical ventilation with heat or The Passive House standard is energy recovery a set of design principles and a voluntary standard for energy New construction and major efficient buildings created by renovation projects utilize the the Passive House Institute ‘Classic’ Passive House standard, (PHI). Buildings adhering to the which includes a maximum energy Passive House standard are well demand for heating or cooling of insulated and relatively airtight, 4.75 kBTU/sf/yr, a total primary use dramatically less energy, energy demand maximum of often rely on renewable energy 38.0 kBTU/sf/yr, and airtightness sources, and are more resilient of 0.60 air changes per hour (at in the face of power outages 50 pascals of pressure.) Retrofit and extreme weather. They projects can use the ‘EnerPHit’ are also extremely beneficial standard, which relaxes these for the occupants, providing requirements and provides both excellent indoor air quality prescriptive and performance and comfortable temperatures paths to certification, outlined along with balanced, highly in Figure 11.10 Passive House filtered ventilation. The Passive has a strong track record of House standard relies on several delivering savings close to those fundamentals: anticipated—especially regarding energy for heating and cooling— • Insulation of the building further reducing both perceived envelope (optimized to the and actual risk.11 location and project) to minimize heat transfer EnerPHit • Windows that are carefully specified, positioned and The Passive House standard for shaded to provide the retrofits, EnerPHit, relaxes the appropriate amount of heat airtightness and energy demand loss or gain depending on targets compared to the ‘Classic’ the season Passive House standard for new construction, acknowledging • An airtight building envelope that there is little that can be done about the massing of an • Reduction of thermal bridges existing building, the location

Pursuing Passive Passive House & Enerphit be-exchange.org 13 Figure 8: Passive House interiors are typically among the most comfortable available in the marketplace, with excellent air quality due to the balanced and highly filtered ventilation, and much improved acoustics because of the high-performance windows and appropriately insualted exterior walls.

Figure 9: Measuring Passive House Performance

9 8.7 8.6 8.2 7.9 7.7 7.6 7.5

5.6 4.5 Heating Energy (kBTU/sf/yr) Energy Heating

0

48 Units 24 Units 24 Units 6 Units

PH Energy Model Measured Performance

Studies find that most Passive House projects use less energy than estimated in their energy models, especially heating energy. All but one of the multi-unit refurbishments monitored above used less energy for heating than estimated in the PHPP software.11

14 be-exchange.org Pursuing Passive Passive House & Enerphit and size of its windows, existing rather than focusing solely What’s In a Name? thermal bridges, and other on energy efficiency, with factors. EnerPHit also provides principles designed to produce The concept of a Passive House two certification pathways. The the healthiest, most comfortable is sometimes confused with the Energy Demand Method is largely interior while using only a “passive solar” houses popularized identical to the basic Passive fraction of the energy consumed in the 1970s. However, Passive House projects have active heating, House standard, except the by a typical building. This is an cooling, and ventilation systems, demand limits fluctuate based important distinction, as many and are ‘passive’ only in the sense on climate zone (see Figure 11). of our existing buildings are not that the bones of the building—the The Component Method takes a particularly comfortable–they low maintenance parts such as prescriptive approach in which are often too hot or too cold an optimized envelope and high performance windows—do much the individual components need with less than ideal ventilation. of the work before the higher to meet specific requirements Passive House provides superior maintenance mechanical systems depending on climate and air quality through highly filtered are engaged to temper the interior location but not overall heating air at appropriate temperatures conditions. Because of its name, and or cooling demand limits. These and humidity levels, ensures because the Passive House standard was first applied to detached prescriptive requirements can comfortable temperatures on the houses, it is often assumed that differ significantly from those that interior surfaces of exterior walls the standard is only applicable would be calculated using the and windows, and dramatically to small residential buildings. In Energy Demand method. In both reduces the potential for interior fact, it applies to the vast majority cases, an energy model (using the condensation and the mold that of building types, from civic and institutional projects to commercial Passive House Planning Package, often results. For buildings with and large multifamily structures. or PHPP, software) is developed to significant interior air quality or Though developed in Germany, the determine specific parameters for thermal comfort issues, these Passive House standard is applicable each project, based on climate, benefits alone may make a globally and projects have been orientation, and other building Passive House retrofit attractive. certified in nearly every climate zone from equatorial to arctic. characteristics. EnerPHit also The measures required to meet provides a long-term planning these comfort requirements tool that allows the project team often include recladding the to package various upgrades exterior and providing new, more into phases, indicating the ways responsive heating, cooling and in which these upgrades impact ventilation systems—significantly one another and how much each transforming the building as a phase can be expected to save, place to live or work. providing a basis for simple capital In the past, some energy planning. In this study we have efficiency initiatives have focused on the EnerPHit Energy addressed occupant comfort Demand Method. only obliquely, with the needs of the occupants acting as a kind of Comfort and Quality, backstop to attempts at drawing plus Savings down energy use. The Passive House focus on providing the Passive House is organized greatest comfort for building around occupant comfort, occupants remains a fundamental

Figure 10: Passive House Standard Criteria

Heating Cooling Air-tightness Primary Renewable Renewable Demand* Demand* (ACH @50 Energy Primary Energy Energy (+latent) pascals) Demand* Demand* Generation*

Passive House Classic 4.75 4.75 0.6 38 19 - Passive House Plus 4.75 4.75 0.6 - 14.3 19 Passive House Premium 4.75 4.75 0.6 - 9.5 38

EnerPHit (existing buildings) 4.75–11 9.75 1.0 varies 38 varies

*kBTU/sf/yr

Pursuing Passive Passive House & EnerPHit be-exchange.org 15 Figure 11: EnerpHit criteria

Opaque Wall Insulation Windows Ventilation (r-value) Climate Zone Heating Demand Cooling and Exterior Interior U-Value Min. Heat Min. Humidity (according to PHPP) Limit Dehumidification Recovery Recovery (kBTU/sf/yr) Demand Limit

Arctic 11.0 Equivalent to 63 23 0.08 80% - Cold 9.5 Passive House 47 19 0.11 80% - Cool-temperate 7.9 requirement for 38 16 0.15 75% - new construction

Warm-temperate 6.3 19 11 0.18 75% -

Warm 4.7 11 8 0.22 - - Hot - 11 8 0.22 - 60% Very hot - 23 13 0.18 - 60%

Figure 12: Passive House Ventilation Criteria

Passive House Typical / Code Heat recovery efficiency >75% 50% Watts per CFM <0.77 - Coefficient Of Performance >10 - Leakage (@ ERV) <3% - Sound <25 dBA -

The Passive House standard includes a variety of performance requirements for ventilation systems, many of which are either less stringent or not addressed in US codes.

(and fundamentally positive) the unit itself, and the sound distinction that recommends experience by the occupants, the this approach. last a rather unique criteria that In addition to the energy speaks to Passive House concerns demand and airtightness figures for the comfort experienced by above, the Passive House the occupants and not just the standard includes specific interior hard numbers of energy use. comfort criteria that determine window performance and dictate construction detailing at locations of potential thermal bridging, such as the window installation details. More details on thermal comfort are included later in this report. There are also efficiency criteria for the ventilation systems, mitigating against simply adding fresh air without regard for the energy costs of doing so. To meet these criteria, Passive House projects must utilize heat- or energy-recovery ventilation systems. Beyond the efficiency of heat recovery the requirements include a cap on the amount of energy used to deliver each unit of air (in cubic-feet-per-minute, or CFM), the leakage within

16 be-exchange.org Pursuing Passive Passive House & EnerPHit retrofit criteria

Figure 13: Design Condition Assumptions

Design Condition Winter Summer Outside 14.4 F 70 F (wet bulb) / 86.8 F (dry) Interior 68 F / 25% RH 77 F / 50% RH

Design conditions assumed for the purposes of studying strategies in the PHPP energy modeling software.

Figure 14: Passive House Performance Criteria vs. Existing Conditions

PH Criteria Proposed Existing Delta Heating energy demand* 6.34 6.33 35.11 82% Cooling energy demand* 5.71 4.66 5.8 20% Primary Energy Demand* 39.93** 36.58 99.44 63% Primary Renewable Energy Demand* 60/45/30 30.17 123.14 75% *kBTU/sf/yr **varies with project parameters

Airtightness (ACH 50) 1.0 1.0 5.0 5X Window U-value (average) 0.18 0.144 0.8 5X Walls (R-value) - 10.0 2.4 4X

Comparison of i) the criteria to meet the EnerPHit standard, ii) the estimated performance of the proposed retrofit, and iii) the existing conditions, where known.

Figure 15: Thermal Bridging Performance vs. Existing Conditions

Thermal Bridge Before* After* Delta Parapet 0.55 0.17 3X Perimeter Beam @ Floor Slabs 0.20 0.04 5X *BTU/(h-ft-F)

Teams pursuing Passive House must demonstrate that the primary thermal bridges through the envelope are mitigated to protect against interior condensation, heat loss and thermal comfort problems inside. Two examples are included here.

Pursuing Passive Retrofit Criteria be-exchange.org 17 retrofit strategies

Multiple strategies have been explored in each category to determine the most effective solution that limits disruption to the occupants.

To meet the Passive House- openings at the elevator shafts EnerPHit criteria outlined and fire stairs. The introduction previously, the project team of properly installed, high analyzed available options performance windows will for each major category have a dramatic impact on the of improvement: envelope airtightness of the building as a (insulation, airtightness, and whole. If an exterior-insulation- windows), heating and cooling and-finish-system (EIFS) is applied systems, ventilation, and to the exterior the adhesive itself domestic hot water systems. will act as an air barrier across the opaque wall surface. A series of remedial measures would improve Envelope the airtightness of the shafts, fire stairs and existing duct risers. A high performing envelope is the foundation of the Passive Insulation House standard, with a significant emphasis on airtightness, the right amount of insulation, and high EnerPHit Target R-10

performance windows and doors. Existing R-2.4

Proposed Airtightness Install new exterior insulation system

EnerPHit Criteria 1.0 ACH Existing 5.0 ACH Walls: As with any large multifamily building, the building Proposed under consideration possesses New airtight layer at façade, carefully a low ratio of exterior envelope detailed window install, correct shaft issues (walls, windows and roof) to occupied interior space. Coupled with the limited area of windows It is assumed that major points (only 21% of the exterior walls), of infiltration through the this produces a building whose existing building exterior are the loads are not dominated by windows (including the perimeter envelope losses or gains. As such, condition, the operable sash our analysis finds that only an connections, and the window additional R-10 must be added to AC units) and the roof level the exterior walls. This translates

18 be-exchange.org Pursuing Passive Retrofit Strategies Passive House and the Law of Expanding Returns

The development of US energy codes are might reduce spending in other areas. In envelope performance and the heating driven by two primary factors that obscure our insulation example, imagine if rather and cooling systems. The fact that Passive the advantages of high performance than providing just the code mandated House is seen as such a revelation by so components and systems. The first is R 10 wall, providing an R 30 wall allowed many in our industry speaks to the manner that our codes focus on the performance you to significantly downsize your heating in which our current code paradigm of individual elements rather than their system. In that scenario, increasing the has quietly shaped the way we look at holistic impact on overall performance amount of insulation may actually result in decisions about building performance. of the building, and the second is using spending less money. Even if something like the full Passive the concept of diminishing returns to The opportunity costs of this paradigm House standard is not adopted as our determine cost effectiveness of individual in terms of carbon emissions is significant. energy code, it will be a huge improvement components. Sometimes increased performance can if the principles embedded in the standard First, the performance requirements reduce first costs. become our typical approach to design of various building components, whether Certainly, there is little about our codes decisions, altering both the cost and these be window units or the insulation that precludes project teams from pursuing performance of our buildings positively. of exterior walls, are evaluated on a holistic solutions that take advantage component by component basis with little of the type of synergies described here. Postscript: This piece owes a great regard for how these choices might impact And the role of our codes is to act as a debt to the work of Amory Lovins of the one another. For instance, all other things backstop, to determine the minimum Rocky Mountain Institute. For a deeper being equal, the selection of extremely that must be provided, not to establish exploration of these concepts we highly high performing windows may allow a industry leadership. But our codes are the recommend Natural Capitalism: Creating project to install less insulation to meet the central reality of the building industry, the Next Industrial Revolution which he project’s demands, or vice-versa. Currently setting the tone for virtually all design and co-authored with Hunter Lovins and our energy codes provide prescriptive construction decisions. Paul Hawken. criteria for both, without regard to how Passive House has been designed to they impact one another. Under this take advantage of the interaction between paradigm, you don’t get to reduce your levels of insulation because of your high performance windows. Despite the fact that higher performing elements might pay for themselves many times over across their life span while providing far superior comfort, our prescriptive code paradigm masks their cost effectiveness and reduces the chance that they will be considered. Second, the performance criteria of specific components are generally selected by determining a point of diminishing Cumulative resource savings returns. Take insulation as an example: the first few inches of insulation in an exterior wall assembly are the most critical inches. Moving from a wall with R1 to an Marginal cost of efficiency upgrade of efficiency cost Marginal wall with R5 provides a huge step forward in performance, both in terms of comfort and saved energy, for very little cost. 1 The greatest resource savings of a 3 In certain scenarios, increasing Moving from R5 to R10 you begin to see given component are achieved with performance of one element can diminishing returns on the dollars spent the first upgrades to performance, for have dramatic impacts on efficiency. for each unit of increased performance. instance, going from single to double A high performance window, for It is at this point that codes professionals glazed windows. instance, might allow a project to typically determine that it is no longer forego providing heating at the cost effective to increase the performance 2 Our energy codes typically set window interiors. of the component in question, and set performance requirements based on the prescriptive requirements for that the moment of diminishing returns— 4 Taken together, the more expensive element. This criteria is perfectly sensible the point at which the direct returns window has resulted in eliminating with regard to the individual component per dollar spent on improved the cost of the heating system—so in question, but discourages consideration performance declines. the higher performance option is less of those occasions when increasing the expensive. performance of a particular component

Pursuing Passive Retrofit Strategies be-exchange.org 19 to 2” of R-5 XPS insulation, or (EIFS), or a ventilated rainscreen, Figure 16: EIFS Detail 2.5” of R-4.2 rigid mineral fiber both of which require scaffolding board. Many people assume the entire building exterior. Existing masonry EIFS that pursuing Passive House requires adding a large quantity EIFS: Installation of an EIFS of insulations in walls and roofs, system requires mechanically but this is typically the case only fastening a layer of exterior in smaller buildings with a high sheathing to the existing brick to ratio of exterior surface to interior produce a clean, stable substrate. space. Conventional energy (If the existing brick is sufficiently codes usually require the same stable this sheathing layer can amount of insulation in both large be omitted and the insulation and small buildings, whereas can be installed directly against Passive House calculates the the brick.) The required layers of appropriate amount of insulation rigid insulation are then adhered needed (assuming other criteria directly to the sheathing without like airtightness and window mechanical fastening. (Figure 16) specifications are met.) In fact, In this assembly the adhesive is because this specific building actually the air barrier. A mesh- Adhesive & Sheathing Stucco has a limited window area and reinforced multi layer coating lacks the more egregious thermal resembling stucco (typically The proposed EIFS system would likely include a layer of sheathing fastened to bridges (like balconies), the wall proprietary) is applied over the existing masonry, with the insulation R-value required by Passive House the insulation to finish the new adhered directly to the sheathing. is actually less than current energy facade. (See Figure 17) The adhesive acts as an air barrier. code. This is not a particularly Insulation needs to return common set of circumstances, at the jambs and heads of each but illustrates the degree to window opening, with a special which Passive House tailors detail for the sills, presumably in requirements to the specifics of metal. It also needs to encapsulate the project. the parapet, including the top and Two basic strategies offer rear faces, with a metal coping themselves to provide the cap over the assembly. This is the additional insulation required to least expensive exterior insulation meet the EnerPHit standard: an option, but these systems have Exterior Insulation & Finish System a history of moisture problems

Figure 17: EIFS typically utilizes expanded polystyrene board insulation. The product shown here utilizes recycled wood fibers, providing the requisite thermal properties with far lower life cycle costs.

20 be-exchange.org Pursuing Passive Retrofit Strategies related to fine cracks that can complementary uses for the Figure 18: Rainscreen Detail develop in the stucco finish, building roof area, including green allowing water to seep behind roofs (to supplement insulation, Existing masonry Rainscreen this outer layer where there is reduce the heat island effect, no system to allow the moisture improve stormwater performance to drain back out of the wall and provide wildlife habitat), as assembly. Regardless, these well as the potential installation of commonplace EIFS systems photo-voltaic systems. Insulation represent the most cost-effective will also be required on the inside means of improving the insulating face of the parapet above the roof. properties of the wall while limiting air infiltration. Windows

Rainscreen: These systems are more expensive than EIFS EnerPHit Target U=0.18 systems, but can produce Existing U=0.80 an extremely durable façade system with a wide variety of Proposed Replace existing windows with PH-certified, aesthetic options, most of which triple-glazed windows, with appropriate significantly increase curb install details appeal. (Figure 18) Rainscreen systems require frequent points at which the faced system connects mechanically to the Passive House requires careful existing building structure. selection of high performance These penetrations are costly, windows to ensure interior but also interrupt the otherwise comfort and to optimize heating continuous layer of exterior and cooling demand. To maximize insulation. This requires careful comfort and reduce the potential While more expensive, a rainscreen system detailing and may result in the for condensation, these windows provides a far more attractive and durable need for additional R-value of often require triple-glazing, exterior facade that should not suffer the insulation to compensate for the though not always in transitional maintenance challenges often experienced with EIFS products. penetrations in the insulation spaces such as lobbies or common layer. (Though many systems areas. Passive House windows are now available that include meet stringent standards for elements with low thermal airtightness and thermal bridging conductivity, like fiberglass.) with continuous gasketing, robust Rainscreen systems allow for the hinging and locking mechanisms, installation of façade components and frames incorporating (insulation, air barrier, sheathing, extensive thermal break materials. etc.) in the correct order and in a Passive House determines manner allowing for easier long the window performance term maintenance. (Figure 18) requirements based on several Properly constructed rainscreen systems should not suffer from the moisture problems often associated with less expensive Figure 19: Available Passive House Windows façade systems, like EIFS. Frame Mtl. U, total U, Frame U, spacer Roofs: A total of R-23 is needed at the roof, easily reached with Schuco Alum. 0.144 0.176 0.031 2” of XPS insulation board, and Heroal Alum. 0.13 0.13 0.022 not dissimilar to the insulation Schuco uPVC 0.114 0.134 0.016 board that exists currently. Munster uPVC 0.13 0.15 0.022 This can easily be included when Aluplast uPVC 0.14 0.19 0.022 the roof membrane requires replacement. Any roof membrane Several manufacturers offer products in the US that meet Passive House requirements, replacement program should be a market that has been growing significantly each year. prepared to accommodate other

Pursuing Passive Retrofit Strategies be-exchange.org 21 Figure 20: The primary Passive House window The following table compares the U-value requirements of criteria are as follows: the Passive House windows with that of the existing and that mandated by current code.

Assumptions PH Window U-value 0.18* Winter design temp 14.4 °F Existing U-value 0.8 Installation PSI value** 0.023 Delta 5X Window Criteria Code U-value .55** U-glazing* 0.115 Delta 3.4X U-frame* 0.155 Glazing edge** 0.020 *Assumes carefully detailed installation that mitigates thermal Solar Heat Gain Coefficient 0.325 bridging at window perimeter. (A poorer installation would require a more stringent U value.) *BTU/h/ft2/F **BTU/hr-ft-F **Code U values do not take installation conditions into account.

Figure 21: Existing Window Although the frames of the proposed Figure 22: Proposed Window Passive House certified windows Passive House windows are larger than the existing, because the benefit from generous thermal breaks within the frame, typically retrofit would allow for the elimination of window AC units the include triple glazing, and, perhaps most importantly, include daylight area of the windows are effectively increased by about 15%. gasketing and hardware that ensure airtightness.

factors, including the size of each by the local context. Standard window opening, the interior energy codes do not calculate the conditions and thermal bridging losses associated with varying characteristics of the window installation details. installation. Another primary The availability of Passive driver is the winter exterior design House certified windows in temperature assumed within North America, while limited, the PHPP software. The thermal is increasing steadily. To reach comfort requirements for New the US market, windows must York (in the PHPP) are currently not only meet Passive House based on an exterior design standards but must also temperature of 14°F. EnerPHit fulfill National Fenestration allows some exemptions if heat is Rating Council (NFRC) and delivered at the window surface. other US certifications. Many The required window criteria for a manufacturers of Passive House project is partially dependent on certified windows specialize in assumptions about the thermal wood frame units, which are the properties of the installation norm in Europe, even in multi- itself, since the performance of story buildings. Here in the US, a window is directly impacted wind load requirements typically

22 be-exchange.org Pursuing Passive Retrofit Strategies Passive House Windows itself, the leakage increases opportunities delta is not reached on the coldest day of Passive House windows differ significantly for condensation and discomfort. Under the year. As a result, a person wearing a from typical windows, with far higher our current testing procedures, a poorly thin shirt can sit next to a Passive House performance regarding both energy use designed leaky window can have the same window in winter, and not feel a chill. and human comfort. total U-value as a highly airtight unit. Although double-glazing may The former will perform far worse than the be sufficient in common areas and US energy codes view window latter, but the consumer has no reasonable hallways—places where occupants performance primarily through the prism means of telling the difference between are rarely sedentary near the glass for of heat transfer of the total window unit, them. Many window experts would go long periods—triple-glazing is typically without isolating the performance of so far as to say that the airtightness of required for Passive House projects. But individual components (the frame itself a window unit is more important than Passive House certified windows are more vs. the glazing unit, for instance) and with the U-value, but our energy codes do than just triple-glazed, they meet stringent only nominal limits on air leakage. While not requiring testing that would inform standards for airtightness and thermal this certainly simplifies the testing and decisions on this basis. bridging with continuous gasketing, robust selection of windows, it produces energy hinging and locking mechanisms, and and comfort compromises by allowing Enter Passive House frames that incorporate extensive thermal one component with relatively strong break materials (Figure 22). It is probably performance to obscure poor performance Passive House tackles window true that the airtightness, thermal breaks in other areas. The components of performance by looking primarily at their and other measures are as important to window units that directly impact contribution to interior comfort, and the overall performance of Passive House performance include i) the frame itself with regard to heat transfer they assume windows as the triple glazing. In general and the makeup of any thermal break, ii) windows should provide energy balance. terms, it is better to have a tight window the operating sashes and their hinging As such, the window criteria in Passive than a low U-value, but best to have both. and locking mechanisms, iii) the spacers House includes individual U-values for both (often aluminum) at the edge of insulated the frames and the glazing components glazing units (IGUs), iv) the gas (often air, (not just the total U-value) and they include sometimes argon) between glazing panes, stringent airtightness requirements. and v) the number of panes of glass. Each Here in the US we see windows of these can impact the other quite directly. as a breach in the envelope, with the You may have an aluminum frame with an performance of the window unit mitigating excellent thermal break, but aluminum (slightly) the energy losses through the spacers in the IGU can effectively opening. One goal of Passive House bypass the thermal break, increasing the is to configure the placement, area, potential for condensation and amplifying performance and installation of windows discomfort for those near the windows. such that the heat losses are lower than the A typical code compliant window, annual solar heat gains through the glazing, for example, will require that the interior meaning that the windows reduce total surface be conditioned by a heating or heating demand rather than increase it. cooling system at certain times of the A fundamental element of this year to avoid condensation and mitigate perspective is basing window performance discomfort. A high-performance window, requirements on the specific climate however, might eliminate the need for that impacts of the location. Our energy codes perimeter heating and cooling system, but already do this to some extent, requiring this cost reduction is rarely considered different U-values for different climate when we evaluate the cost effectiveness of zones around the country. But Passive the window. House takes this to a far more granular Additionally, testing for U-values in the level, using the peak temperature extremes US is done with equal pressure on either in a specific location to determine the side of the window unit, a lab condition overall U-value of the window units and that is effectively never encountered in using interior comfort as an additional real life. Pressure differences are often consideration beyond heat loss. Passive quite severe and air leakage (around the House starts by asking that the interior window glazing, at hardware locations, or surface of the window never be more than at the sashes) bypasses the performance seven degrees Fahrenheit different than the of the individual window components. air temperature of the room (the threshold This convection heat transfer actually at which people feel discomfort because increases the conductive heat transfer. of radiant heat transfer.) The window and Not only is heat lost (or gained) via the air glazing U-values are set to ensure this

Pursuing Passive Retrofit Strategies be-exchange.org 23 necessitate aluminum frame House windows are typically of Figure 23: Heating and Cooling units, or polymer based frames the casement or tilt/turn type, the Reductions with metal reinforcement. Figure windows may need to be designed 19 lists several of the windows to accept a window AC unit 35.1 that currently meet both the for several years, with the void Passive House criteria and other replaced by triple glazing when requirements for this project, a new cooling system is finally including the Shuco unit modeled in place. There is no technical and priced for the feasibility study. impediment to this, but window manufacturers do not currently Phasing: There are effectively two offer units specifically suited options for window installation. to this purpose and will need a

kBTU/sf/yr The most effective method is strong market indicator before

82% Reduction to install new windows from they are likely to invest in the the exterior when the exterior required research.

6.3 Reduction 21% 5.7 insulation system is installed, thus 4.7 utilizing scaffolding once and limiting disruption to the tenants. Heating & Cooling However, if the building owner Heating demand Cooling demand wishes to delay the expense of Once improvements to the Existing* EnerPHit implementing exterior insulation, envelope are complete, (demand it is feasible to install new windows heating and cooling demand is method) from the interior, realizing dramatically reduced. (Figure 23) * Based on energy modeling, calibrated significant comfort and energy to utility bills cost benefits. Because the new Heating high-performance windows so Upgrades to the building envelope, dramatically reduce air infiltration, including new exterior insulation, EnerPHit Estimate 6.3 kBTU/sf/yr airtightness and high-performance best practice suggests installing windows, result in a 80+% reduction in a balanced ventilation system as Existing 35.1 kBTU/sf/yr heating demand and 20+% cooling demand. soon as possible after the window installation, to ensure that the Proposed Remove steam radiators, install VRF system tighter envelope doesn’t create with rooftop condensers and cassettes in unhygienic conditions. Careful each major room positioning of the new window will be critical to avoid thermal bridges when all phases of the retrofit are complete. The heating demand reductions of more than 80% allow for either Phased Retrofits and Window scaling back the existing steam AC: Passive House window delivery system or replacing this performance criteria essentially system with something providing precludes the use of double-hung far smaller capacity and far windows. The “meeting rail” greater efficiency. connection between the upper Our analysis indicates that and lower sashes and limited the heating demand is so low engagement offered in the sliding that the heat produced by the track at the jambs is simply too steam risers, not including the weak to meet the airtightness radiators, is sufficient to meet and thermal break requirements the overall heating demand for a essential to both human comfort significant portion of the year. Put and energy savings. Assuming another way, with a fully improved that a window replacement envelope, even with the radiators program will occur prior to turned off apartments will the conversion of the heating experience periods of overheating and cooling system, provisions in the shoulder seasons solely must be made to accommodate due to the heat from the risers. window AC units in the period Given the size and quantity of between new windows and new the steam risers in the building, cooling systems. Because Passive the heat output of the risers

24 be-exchange.org Pursuing Passive Retrofit Strategies could meet 40% of the annual Changes to the cooling system heating load of the fully improved however, are not driven primarily envelope, which is over 50% of by cooling demand but by the the heating season. The potential fact that window air conditioning for overheating will necessitate (AC) units do not meet the a steam riser control system to comfort and envelope criteria prevent overheating even when all of Passive House. With regard apartments have the radiators off to comfort, window AC units because the room temperature set and the assemblies required point is satisfied. for their installation represent Phasing out the steam heating significant thermal bridges, system is further complicated impairing thermal comfort and because the steam system that raising the risks of condensation. serves the building is actually The airtightness of these units a small district system, serving is also substandard, and even a total of three buildings. A if the units are provided with building by building conversion a carefully designed thermal will be required to achieve the full jacket in the winter months, their efficiency of the retrofit upgrade. installation almost universally For the purposes of this study, we results in a porous element in the assume the full conversion of this exterior façade. They are also not building includes the removal of particularly efficient. (See also the steam boiler system. “Phased Retrofits and Window AC” above.) These issues require Cooling the introduction of a cooling system other than window units. Through-wall, packaged EnerPHit Estimate 4.7 kBTU/sf/yr thermal air conditioning units

Existing 5.7 kBTU/sf/yr are another common solution in New York and around the United Proposed States. While these represent an Remove window AC units, install VRF system improvement over window units, the same issues regarding thermal bridging and airtightness preclude The cooling demand reductions, a PTAC system from meeting the while more modest, will result requirements of Passive House. in significant electricity savings. (In the Optimal Plan later in this

Heating & Cooling Options in every major room in the building to contributor to climate change and one insulate this piping would be costly and of the primary advantages of a central The study assumes that heating and seems an untenable level of intrusion AWHP plant is that the refrigeration cooling demands are met by the while the building is occupied. The system would be packaged and the introduction of a Variable Refrigerant other option would be to run new refrigerants charged in the factory, Flow system, described elsewhere in hydronic piping on the exterior of the greatly reducing concerns about leakage this section. building, similar to what is proposed when compared to a VRF system. Converting the existing steam for the refrigerant lines. In either case, A third option might be the provision system to a hydronic system is a the existing radiators would need to be of water source heat pumps in each common upgrade for buildings of this replaced with appropriate fan-coil-units. apartment connected to a condenser type and, while possible, it seems a The most effective centralized water loop whose water is heated by less attractive option when the various solution would likely be an air-to- a central AWHP plant and cooled by a challenges are considered. Among the water heat pump (AWHP) plant that heat rejection plant like an evaporative most attractive aspects of a steam-to- delivered hot and cold water to the cooling tower on the roof. In addition to hydronic conversion is the potential selected distribution system. While the significant hydronic piping required, to use the existing distribution piping there is not currently a well developed the units in each apartment would each (though not the radiators) to serve the market of heat pumps at the scale of take up about four square feet of space. interior spaces. However, since chilled this application it might be feasible Given the above issues, refrigerant water would be delivered in the 40-50 to install a high efficiency boiler and leakage concerns notwithstanding, at F temperature range, all the piping rooftop chiller system now and replace time of writing a new VRF system seems would need to be insulated to avoid it with an AWHP plant when they are the most effective solution. condensation. Opening the pipe chases available. Refrigerant leakage is a major

Pursuing Passive Retrofit Strategies be-exchange.org 25 section we discuss the significant A compressor and heat exchanger potential for high-performance are located in an outdoor packaged units to improve the unit. Refrigerant is distributed viability of deep retrofits.) throughout the building to fan-coil Another option is to convert units (FCUs) where the refrigerant the steam system to a hydronic heats or cools air as needed. system, which entails replacing The ability of the system to the steam boiler with a hydronic operate at varying speeds allows plant, replacing the steam for efficiency and greater control radiators in every room with of interior temperature. Fan Coil Units, and introducing The terms most commonly a new cooling tower assembly, used to describe refrigerant- presumably on the roof. This is based air conditioning systems a somewhat common upgrade can be a little confusing. The term for post-war buildings, but it is “VRF system” typically refers to expensive and complicated to larger systems with expansion implement and, all other things valves at the FCUs that allow being equal, often costlier to for longer piping runs, a greater operate (due to pump and fan number of FCUs on each energy, among other things) refrigerant loop, and in some than the other primary option, a cases, heat recovery. Although Variable Refrigerant Flow (or VRF) VRF systems are, technically, system, detailed below. “heat pumps,” this term usually The overheating issues refers to smaller systems utilizing described above essentially variable speed compressors. preclude the continued use of the Often found in homes or small steam system, and the existing commercial spaces, these window AC units do not meet systems are also often referred Passive House requirements. to as “mini-splits,” “ductless,” or To meet the heating and cooling “ductless mini-splits.” Whatever demands of the project we elected the terminology, the fundamental to study the installation of a new technology of these various VRF system. See the Heating & refrigerant based systems remains Cooling Options sidebar for more essentially the same. details on this choice. VRF systems have several benefits compared to more traditional systems, offering a Variable Refrigerant Flow much higher level of control than Systems (VRF) ducted systems, and they can be much quieter. Standard hydronic Commercialized in the 1980s, VRF systems also provide a high level systems use refrigerant as the of control, but pump and fan medium for cooling and heating. energy to operate them can be

Figure 24: Similar to "mini-split" systems, VRF systems utilize interior cassettes to deliver heating and cooling. A unit similar to the one shown here would sit above the window in each major room, replacing the steam radiators and window AC units.

26 be-exchange.org Pursuing Passive Retrofit Strategies Figure 25: Distributed VRF Diagram

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In a distributed VRF arrangement, a small tower would be constructed at one end of the building to house condensing units serving each floor. Refrigerant lines would run above the ceiling in the hallway and serve cassettes mounted above each foyer. Small ducts would deliver tempered air to adjacent rooms.

excessive, making those systems Refrigerants require new refrigerant lines or other less attractive from an energy equipment replacement—an expensive efficiency perspective. While Variable Refrigerant Flow (VRF) and disruptive prospect. Leakage of In Passive House projects, systems such as the one described HFCs can occur during installation, in this report offer high efficiency commissioning and disposal of the a common problem is that the and other important benefits, there systems, so training installers is critical smallest heating and cooling remain concerns about the significant moving forward. How critical? If the units available are far larger than global warming impact of the leakage is high enough, the global is necessary. Even VRF systems hydroflourocarbon (HFC) refrigerants warming impact of the HFC could are somewhat too large in most utilized within these systems. Although potentially outweigh the benefit of not refrigerants that severely deplete burning fossil fuels over the life of the cases, although they do offer the ozone have been largely phased out system. lowest capacities on the market since the 1987 Montreal Protocol, their VRF systems have a prominent when compared to other options replacements—mostly HFCs—are very role to play as we drive toward providing both heating and potent greenhouse gases. Recognizing electrification of the built environment, cooling. this impact, in 2016 roughly 200 but ensuring they are installed and countries signed the Kigali Accord, a maintained appropriately and that there In buildings that may commitment to dramatically reduce is a smooth transition to refrigerants experience the simultaneous the use of HFCs by 2050. Kigali was a with low global warming impact will be need for heating and cooling due remarkable show of global unity, but incredibly important if we are to meet to differences in internal gain or HFC replacements are proving difficult our climate action goals. excessive solar gains in some areas, to find. Those looking to utilize VRF systems A fuller treatment of this issue VRF offers the ability to recover must contend with the possibility that is available here: heat from one side of the system the specific refrigerant the system is https://www.buildinggreen.com/ and provide it to the other. This designed for might be phased out, feature/cost-comfort-climate-change- heat recovery option improves and that the replacements might and-refrigerants the performance of the system but typically requires additional controls and, in some cases, extra refrigerant lines. This type of system is ideal for office spaces with differing uses spread around the building and for hotels where occupants have varied temperature requirements. Heat recovery is not included in this proposal. In the subject building, a

Pursuing Passive Retrofit Strategies be-exchange.org 27 VRF cassette would replace access to the exterior would each existing steam radiator, require significant reductions with the cassette mounted in one or more apartments, over the window above the which seems untenable. Another existing radiator (Figure 24). This distributed option is to build a arrangement frees up a portion small footprint tower at one end of of floor area. Coupled with the the building to carry condensing removal of the window AC units units. An obvious location for and the high performance of the such a tower is the north façade windows themselves, it will now of the building. The new tower be feasible to sit comfortably would likely be clad for aesthetic directly next to these windows purposes but would not need to in all seasons. Assuming this include conditioned space. The configuration frees up space next condensing units in this tower to each window that is the width would deliver refrigerant along of the window and 3 feet deep, the spine of each floor to serve the retrofit adds roughly 4,000 a ceiling-mounted VRF unit in square feet to the usable area of the foyer of each apartment the building. (Figure 25). This option would There are two primary options be relatively expensive, given for deploying a VRF system: the need to build the small distributed or centralized. mechanical tower, and the interior runs of refrigerant (including Distributed VRF: In a distributed those through the northernmost arrangement, condensing units apartments from the condensing are designed to serve specific tower to the interior corridor) zones, presumably one or two would be extremely disruptive to floors, and located throughout the occupants. the building. Unfortunately, in the subject building there are Centralized VRF: In a centralized no extraneous mechanical or arrangement, large condensing common area spaces that might units would be located on the be repurposed for such units, roof serving interior VRF units via and creating such space with vertical refrigerant runs. There are

Figure 26: Centralized VRF, Option 1: Replace Existing Risers

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The existing steam risers serve each major room in the building and could be removed and replaced with vertical refrigerant lines, although this would entail opening these chases from floor to ceiling in every major room.

28 be-exchange.org Pursuing Passive Retrofit Strategies Figure 27: Centralized VRF, Option 2: New Central Shafts

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In this scenario new shafts are created at each end of the hallway, elimianting some closet space in the four end units while providing easy access to the hallway for distribution.

Figure 29: Centralized VRF, Option 2 Schematic three options for locating these scenario (Figure 27), the vertical refrigerant risers, listed from most refrigerant lines would be located disruptive to least: in two newly created shafts at either end of the central corridor. 1 In existing steam riser As luck would have it, there are locations 6-foot deep closets at each end of 2 In new central shafts the corridor. Without understating adjacent to the corridor the disruption this would cause 3 On the exterior of the for the four apartments that would existing façade be impacted, one can imagine that a small portion of these Replace existing steam risers: closets might be considered a The idea of replacing the old reasonable sacrifice for a modern heating risers with new ones is heating and cooling system. If appealing, as they are evenly the chases are the full width of distributed around the perimeter the corridor (4'-8", also the depth of the building, adjacent to each of the back to back closets) radiator which will be replaced the chase would only need to with a new fan coil unit (FCU.) be 6" deep. If one assumes 4" (Figure 16). However, this work shaft wall the closets will have would be extremely disruptive lost only 10" of width. From the to the apartments as the chases risers, horizontal lines would run containing the existing steam along the ceiling of the corridor, riser would need to be opened feeding fan-coil units mounted New central shafts would allow the rooftop in every major room of every at the foyer ceiling of each unit units to directly serve distribution in the apartment on every floor. It is (Figure 29). Reaching bedrooms hallways at each floor. highly likely the old steam riser and other ancillary spaces would piping would require removal. This be difficult, requiring either sort of significant construction running refrigerant to cassettes throughout the building seems serving those spaces, or ducting untenable, though it is technically tempered air from the entrance possible. ceiling units. Both scenarios represent New central shafts: In this significant disruption to every

Pursuing Passive Retrofit Strategies be-exchange.org 29 room in every apartment, of this system is a 160’ foot limit Figure 33: Centralized VRF, especially in the most congested on the vertical distance of any Option 3 (preferred) Schematic areas of the plan—the kitchen cassette from the condenser, and bath spaces adjacent to the as well as a 100 foot limit on corridor. Although this scenario the vertical distance between requires a single supply and any cassettes served by single return riser for each floor rather riser. Due to this, each “stack” than for each stack of cassettes, of cassettes would be divided the increase in horizontal piping into upper (floors 8-15) and required means that more material lower (floors 1 to 7) portions with is required than the other options. separate supply & return risers. Another barrier to this scheme (See Figure 33) Small penetrations is headroom in the hallway. The through the existing masonry most viable ventilation option would be required at each will include a wide duct along cassette location, to minimize the ceiling of the hallway, leaving interior refrigerant runs. little space for refrigerant piping, and necessitating crossovers that would certainly drop below VRF & Recladding comfortable levels. One consequence of the exterior riser arrangement is that the Exterior risers: The most plausible refrigerant lines would have to scenario is to run vertical be installed in the same phase as refrigerant lines on the outside the exterior recladding system of the building with each supply/ (whether EIFS or rainscreen.) In this option each rooftop condenser unit return pair of risers fed by a In either case, 4" of additional serves a "stack" of cassettes, one per floor. rooftop condensing unit (Figure 30). insulation would be added to Vertical distance restrictions require that separate supply and return refrigerant lines The new VRF cassettes would be provide depth for the insulated serve the lower and upper floors. located above the major windows riser lines, with the 2" of insulation in each apartment and to avoid required to meet Passive House crossover of lines on the façade, over that. (See Figure 32) With a supply and return would run this arrangement, a rainscreen vertically on opposite sides of the cladding system would be highly windows. The primary restriction preferable to an EIFS system:

Figure 32: Refrigerant Lines Detail

Interior plaster

Exg. concrete block

Exg. brick

3 layers, 2” insulation

1" Refrigeration Piping Piping Insulation

Installing the refrigerant lines on the exterior requires additional insulation to maintain a flat façade (and to maintain the continuous 2" required to meet Passive House.) The need to remove and patch EIFS to service these lines recommends the rainscreen recladding over the EIFS.

30 be-exchange.org Pursuing Passive Retrofit Strategies Figure 30: Centralized VRF, Option 3: Risers on the Exterior

Living Room Living Room Bed Room Living Room

Bed Room Living Room Bed Room Living Room Bed Room

Kitchen Kitchen Kitchen Bath Bath

Bath Kitchen Foyer Foyer Foyer F Kitchen Foyer Bath Elevator Bath

Bed Room Bed Room

Bath Bath B Foyer Foyer

Living Room Bath Living Room Bath Bath Bath Kitchen Kitchen Living Room Living Room Bed Room Bed Room Kitchen Kitchen Living Room Living Room Kitchen Kitchen

Dining Dining Dining Dining

Return Supply Cassette

The preferred VRF option limits interior construction by placing the new refrigerant lines on the outside of the existing masonry walls and directly accessing the new cassettes over each window.

Figure 28: Proposed Wall Section any future work on the buried refrigerant lines could be done without permanent aesthetic impact because the visible cladding is removable. With an New high performance EIFS system, any future work window would require cutting away the stucco exterior and re-patching, with predictably poor aesthetic Brick and results. masonry wall

Rainscreen Ventilation

Removed steam radiator EnerPHit Criteria 75% efficient Finish Floor (energy recovery), Insulation humidity control Existing No heat recovery, no humidity control Proposed New VRF Cassette Convert existing exhaust system to balanced system utilizing rooftop energy recovery ventilation units

Ventilation represents an underappreciated component of the quality of interior spaces. The need for balanced and properly The fully retrofitted envelope includes new recladding with sufficient insulation as well as high-performance windows, filtered fresh air receives far less while the new VRF cassettes are installed above the window attention than heating and cooling in each major room. systems but has just as significant

Pursuing Passive Retrofit Strategies be-exchange.org 31 Figure 34: Existing Ventilation Plan

Living Room Living Room Bed Room Living Room

Bed Room Living Room Bed Room Living Room Bed Room

Kitchen Kitchen Kitchen Bath Bath

Bath Kitchen Foyer Foyer Foyer F Kitchen Foyer Bath Elevator Bath

Bed Room Bed Room

Bath Bath B Foyer Foyer

Living Room Bath Living Room Bath Bath Bath Kitchen Kitchen Living Room Living Room Bed Room Bed Room Kitchen Kitchen Living Room Living Room Kitchen Kitchen

Dining Dining Dining Dining

Kitchen Bathroom Cooridor

Most ventilation systems of this era perform only adequately, relying heavily on infiltration from the exterior (and adjacent apartments) to make up air exhausted from kitchens and bathrooms.

Figure 31: VRF Scenario Matrix

Pros Cons 1 Replace Steam Risers Tenants: No loss of interior square footage Tenants: Major disruption to every Phasing: Strong flexibility major room in every unit Efficiency:Close proximity to FCU units

2 New Interior Chase Tenants: Somewhat limited in-unit disruption Tenants: End units (4) lose 10” of closet space (except end units) relative to scenario 1 Phasing: Not dependent on other phases Tenants: New ceiling mounted FCU locations needed Tenants: Piping/Ducts needed to rooms off corridor

3 Exterior Risers Tenants: Least interior disruption Cost: 4” additional exterior insulation Tenants: FCUs in same location as exg. Radiators (for flat facade) Materials: Less linear feet of refrigerant piping Phasing: Vertical risers must be installed with exterior insulation

an impact on the comfort and these systems rely on fresh air health of occupants. Despite that is typically provided at the this, many live or work in spaces corridors as well as random with less than ideal ventilation, infiltration through the windows and some significant portion and gaps in the exterior envelope. of buildings have ventilation (Many post-war buildings have systems that are almost entirely corridor exhaust as well, and no non-functional. The multifamily mechanical supply air at all.) This residential market is dominated by infiltration air is often the source exhaust-only ventilation systems of moisture that leads to mold that draw air out of kitchens and formation and can be the source bathrooms and exhaust it to the of asthma-inducing contaminants exterior, often at the roof. To like PM 2.5 and ozone. Common replace the volume of air pulled areas such as corridors usually out of the building by the exhaust, have separate supply air systems.

32 be-exchange.org Pursuing Passive Retrofit Strategies Figure 35: Energy Recovery Ventilation units similar to this Swegon unit would serve the new ventilation system, resulting in highly filtered, balanced fresh air delivery at a minimal energy cost.

Engineers often argue that Existing Ventilation System pressurizing the hallways prevents smells from transferring from the The existing ventilation strategy of apartments into the corridors and the subject building is typical for thereby bothering the neighbors. the type and age of the building: However, negative pressures in stale air from the kitchens and apartments often result in air baths in the apartments, as well being drawn between these areas as the corridors, is exhausted out through common walls, spreading of the building and fresh air is odors and reducing both the supplied to the corridors on each effectiveness of the system and floor. Vertical duct risers located the comfort of the occupants. throughout the building extend The Passive House standard from the lowest floor up to the requires balanced ventilation that underside of the roof where they delivers properly filtered supply combine and then connect to air directly to habitable spaces, three roof-top fans: one for the while stale air is removed from kitchen exhausts, one for the bath kitchens, baths, and laundries. exhausts and one for the corridor This approach is made possible exhaust air (Figure 34). In older, in part by the airtight envelope less airtight buildings, exhaust- which in addition to benefits only systems have been shown mentioned elsewhere (improved to provide adequate (but not air quality, air temperature, and excellent) ventilation if properly acoustics) ensures the balanced designed and air sealed—though ventilation draws little air via it must be stressed that most infiltration from the exterior or ventilation systems of this post- adjacent apartments. Passive war era are neither designed or House ventilation systems must maintained properly. However, also be at least 75% efficient, exhaust-only systems in a building which necessitates the use retrofitted to Passive House of energy or heat recovery airtight standards will be unable units (ERVs/HRVs) to handle to provide the desired fresh air temperature and moisture from the exterior and instead will differentials in the supply and pull air from neighboring hallways return streams. and apartments. Conceptually, there are three distinct options for providing ventilation: decentralized, semi-

Pursuing Passive Retrofit Strategies be-exchange.org 33 Figure 36: Floor Plan: Central Ventilation

Living Room Living Room Bed Room Living Room

Bed Room Living Room Bed Room Living Room Bed Room

Kitchen Kitchen Kitchen Bath Bath

Bath Kitchen Foyer Foyer Foyer F Kitchen Foyer Bath Elevator Bath

Bed Room Bed Room

Bath Bath B Foyer Foyer

Living Room Bath Living Room Bath Bath Bath Kitchen Kitchen Living Room Living Room Bed Room Bed Room Kitchen Kitchen Living Room Living Room Kitchen Kitchen

Dining Dining Dining Dining

Supply Bath return Kitchen return Transfer grille

In the proposed scenario the existing ventilation shafts are repurposed, converting the system from exhaust-only to balanced. Rooftop ERV units serve the new supply risers, and transfer grilles allow the reufrbished exhaust lines to extract from each room.

decentralized and centralized. ventilation shafts (Figure 36). A more popular option for Decentralized ventilation: multifamily highrise projects, Individual ERVs/HRVs are this arrangement results in the provided in each apartment, fewest number of ventilators, usually requiring two penetrations preserving valuable floor area through the exterior wall per and easing maintenance. Reusing apartment. an existing central system Finding a location for the will save significantly on duct ventilator can be difficult, installation costs. especially in an existing building The ventilation shafts in in NYC where every square foot of the building under study can space is valuable. Maintenance is be repurposed and the system often a concern with this approach converted from exhaust only to because the filters in each ERV/ balanced. For the purpose of this HRV need to be replaced or study, a centralized scheme has cleaned at least twice a year. been explored. Figure 34 indicates the Semi-decentralized ventilation: location of the existing ventilation A single ERV services all the risers in the building. The kitchen apartments on one floor. and bathroom risers were Advantages include ease of access originally sized to exhaust 50 cfm for maintenance and elimination from each bathroom and kitchen. of problems that can result from The corridor supply shaft was stack effect in the building. The sized to provide the code required primary disadvantage is the need 0.5 cfm per square foot of floor for a large mechanical space on area for that space which equates every floor. to approximately 250 cfm/floor. The proposed design is illustrated Centralized ventilation: ERVs in Figure 36. on the roof or at the base of At the four apartments at the the building (Figure 35) serving ends of the building, the kitchen stacks of floors through central exhaust riser will be converted

34 be-exchange.org Pursuing Passive Retrofit Strategies to a supply riser. Transfer grills will move air from the kitchen Interior Insulation to the bathroom exhaust to help As the building is freestanding and fully material is offered in a thin, rigid board remove moisture and odors from occupied, this analysis focused on the with a layer of plasterboard adhered to the apartment. Small soffits can feasibility and benefits of installing it, ideal for retrofit applications because be constructed to hide the new new windows and applying insulation after being adhered to an existing from the exterior. Although scaffolding interior wall, one can simply apply a supply ducts which can be run a building of this scale is costly, it layer of joint compound and paint. In down the foyers. presents the most likely option because this particular case, adding just one The seven apartments in the the impact on the tenants is limited layer of 30mm (1.2 inch) Aerogel board middle of the floor will receive and because it results in the highest would provide enough insulation to supply air from the corridor performing building with least number meet the EnerPHit component method of complications. The team analyzed criteria. supply shaft. A main trunk line the feasibility of insulating the building Another future option might be approximately 6" x 24" can be from the interior, and while possible, it vacuum insulated panels (VIPs). Only run down the corridor and small raises the following concerns. recently available in commercial 4" ducts can be used to penetrate If insulation is applied in the interior, volume, these panels achieve up to into each apartment to supply both the perimeter beams at floor level R-50 per inch so only a 1/2 ” panel is and the interior partitions that meet the sufficient. However, VIPs are mylar approximately 45 cfm to the living exterior wall represent major thermal wrapped and if they are punctured rooms and bedrooms to balance bridges that impact the heating and (either during construction or later in out the exhaust flows. The total cooling demand as well as the comfort life), the insulating properties fall to flow rate needed for the 7 center criteria. Because of these bridges, effectively zero. apartments is approximately even adding R-50 of interior insulation Despite satisfying the component (equivalent to 10” of XPS insulation method requirements, interior 315 cfm which should be possible board) will not allow the building to insulation does not resolve the thermal to achieve through the existing meet the demand criteria. As a result, bridges that remain at the floors and corridor riser. Thorough duct any interior insulation strategy is interior partitions. The thermal bridge sealing will be required using an possible only if the component method at the floor could be improved by aerosolized product along with is followed. introducing a wedge of rigid insulation To satisfy the component method where the ceiling meets the exterior constant air-flow regulating interior insulation of R-13 is required. wall. If installed two inches deep at (CAR) dampers at each register Achieving this with conventional the exterior wall, and tapered over to ensure that the proper flow insulation materials is not tenable given 20 inches to just ¼ inch, the surface rates can be achieved throughout the 4-5” loss of interior space. Non temperature of the floor above will the building. conventional options include Aerogel, be moderated sufficiently to avoid an advanced insulation product used most condensation issues. Windows To handle the ventilation, this in petrochemical industries for many need to be installed with thermablock study assumes that three Swegon years and recently adapted for the material at the perimeters, reducing Gold rotary heat exchangers building industry. This product is thermal bridging at each opening. If (1 size 50, 2 size 14) replace the essentially a gel that has had its liquid thermablock is not used at the window existing rooftop exhaust fans. component replaced with 90% air, by install, then tempered air would need to volume. It is highly insulating, providing be introduced at the windows to avoid Ducting just under the roof will roughly R-10 per inch. In the UK the condensation. need to be reconfigured such that the exhaust and intake flows through each ERV are within 10% of each other.

Domestic Hot Water

EnerPHit Estimate 6.8 kBTU/sf/yr Existing 14.1 kBTU/sf/yr Proposed Replace existing steam heat exchanger with high efficiency boiler

The study assumes that the existing steam heat exchanger for domestic hot water (DHW) is replaced with a high efficiency gas-fired boiler connected to the existing distribution system.

Pursuing Passive Retrofit Strategies be-exchange.org 35 Other options include EnergyStar rated and elevators to Renewable Energy utilizing air to water heat pumps be higher efficiency models. Although this analysis does (AWHPs) for DHW, but these are not include costs or payback not currently a standalone option calculations for the provision of solar for a building of this scale in this Summary Of Proposed Strategies photovoltaic panels (PV) the Passive climate. Although highly efficient House energy modeling software and widely used in single family Based on the above analysis, the (called PHPP) does allow for easy modeling of contributions from homes, AWHPs have a lower following set of retrofit strategies on-site renewable energy output than boilers and the units are proposed. generation. available in the US cannot meet Using this module within the the simultaneous demands of a 1 New windows + roof PHPP, we can determine that building of this scale. In fact, it installing PV on the elevator tower insulation + airtightness above the roof and across 60% of is common for AWHPs in larger measures (shafts, etc.) the roof area comes to 3,500 square buildings to be paired with a feet on the elevator tower and traditional boiler for use during 2 Centralized ERV supply & 1,700 square feet on the flat roof of winter (when AWHP output return ventilation system PV panels. These are estimated to decreases) or at peak demand produce 52,000 kWh/yr or 178,000 kBTU/yr per year, roughly 16% of the periods. 3 EIFS and sheathing at existing building electricity demand However, as the carbon exterior (incl. airtightness and roughly 21% of the retrofitted intensity of the grid decreases, layer, and VRF risers at building electricity demand. the carbon reduction potential exterior) Recognizing the drive to net-zero of AWHPs grows and it is energy buildings, Passive House now ALT 3: Rainscreen system includes two certification levels for anticipated that systems that can in lieu of EIFS the provision of renewable energy, service buildings of this scale Passive House Plus and Premium. will be developed for the US and 4 Install VRF roof top units, For the case study building Passive other markets. One of the more replace steam radiators House Plus certification would promising recent developments require 19.05 kBTU/sf-yr, or 38.04 with VRF cassettes, connect kBTU/sf-yr for Passive House has been the introduction of CO2- to risers Premium. The figures outlined for based heat pump systems that ALT 4: High-performance this project come to 22.05 kBTU/sf- utilize a “split-system” arrangement packaged units in lieu of yr, which would qualify the project with an outdoor compressor, VRF system for Passive House Plus certification. improving efficiency dramatically (The same figures apply for EnerPHit projects.) and alleviating issues related to 5 Replace domestic hot water interior AWPHs cooling interior heat exchanger with high spaces even in winter. Smaller efficiency boiler multifamily buildings can stack these CO2-based split systems in 6 LED lighting and controls, modules to meet demand. energy efficient elevators, EnergyStar appliances

Lighting These are listed in the proposed order of phasing (see next chapter.) The modeling assumes that all lighting, currently a mixture of compact or linear fluorescent Optimal Plan (Near Future) lamps, is replaced with appropriate LED technology. The analysis and proposed Occupancy controls in common strategies listed above are based areas and back-of-house spaces on products available in the are assumed, to reduce lighting United States today. But a heating levels during unoccupied periods. and cooling option is available in the United Kingdom and Europe that is both more affordable Plugs & Process Loads and represents fewer phasing challenges: high-performance Plug loads are modeled as packaged heating/cooling unchanged in the before and after units. Superficially similar to the scenarios. In the retrofit scenarios, through-wall packaged-terminal- all appliances are assumed to be air-conditioning-units (PTACs)

36 be-exchange.org Pursuing Passive Retrofit Strategies so common throughout the US, would be as follows: these high-performance units utilize heat pump technology to 1 New windows + more efficiently deliver heating Roof Insulation and cooling. Unlike through-wall PTACs, these high-performance 2 Centralized ERV supply & units typically house the ‘outdoor’ return ventilation system coils in an interior enclosure, (w/ in-line heating) obviating the need for an exterior condenser, and only require 3 EIFS and sheathing at two 4" exterior ducts and a exterior (incl. airtightness 1" condensate line opening, layer) massively reducing the thermal bridging, air infiltration and 4 Replace steam radiators discomfort issues associated with with high performance traditional PTACs. The supply packaged heating/cooling and return ducts have self closing units baffles. The units have inverter- driven compressors, which tend 5 Replace domestic hot water to be quieter than the constant- heat exchanger with high speed compressors common to efficiency boiler PTACs in US. In the case of the proposed 6 LED lighting and controls, strategies for our subject building, energy efficient elevators, these units would replace the EnergyStar appliances VRF system, including the rooftop units and entire system of exterior façade refrigerant risers and connections. In addition to significant cost savings, this system would obviate the need to install the exterior refrigerant risers at the same time as the exterior recladding (whether EIFS or rainscreen) is installed. Rather than replacing the entire steam heating system at once, these units could be phased in over time, presumably with each stack of rooms served by a specific steam riser. To ensure the heating demand is easily met, simple resistance heating would also be provided within the newly introduced balanced ventilation system. For heating purposes, these high-performance units would provide supplemental heating directly controllable by the occupants. Further research would be required to ensure that such units could meet the requirements of our cold climate, but they represent a promising potential retrofit solution.

The stages of this optimal plan

Pursuing Passive Retrofit Strategies be-exchange.org 37 retrofit phasing

Although a full retrofit is the least disruptive overall, phasing has been carefully explored so that owners might align upgrades with financial or other milestones.

Most building owners would likely Phasing the work, however, raises prefer to implement a deep retrofit the total project cost by more of this nature in phases over a than 15% due to duplication of significant period of time, perhaps general conditions and startup 15-20 years. Each phase requires costs. Phasing also significantly less capital (and therefore smaller delays full realization of operating construction loans), and allows the cost savings and carbon emissions kinks of each system to be worked reductions, not to mention the out over time. (Financing options myriad benefits to the occupants. are described later in the report.) When one considers how quickly

Figure 37: Long Term Impact of Retrofit Scenarios

800 Total 709

Total 501 Reduction 29%

Total 340 Reduction 52%

60% Target emission savings 1b/sf emission savings CO2 Total 252 Reduction 64%

0 Year 1 Year 10 Year 20 Year 30 Year 40 Year 50

Existing Building Phased Retrofit BAU Retrofit Complete Retrofit

Although a phased retrofit is a far better option than business-as-usual replacements of equipment, performing the full retrofit in a single phase produces significantly improved outcomes, including earlier enjoyment of the full benefits of the retrofit.

38 be-exchange.org Pursuing Passive Retrofit Phasing our City and State carbon replace that equipment once it reduction goals are approaching, has been made redundant by the the timing of retrofit phasing is introduction of new heating and far from academic. If the primary cooling systems. motivation for embarking on such an extensive retrofit is the increase Phases in asset valuation, it would make sense to transform the property 1 Year 0 as quickly as funding will allow. Envelope 1: windows + If an owner does choose to roof insulation pursue a retrofit in phases, the order is influenced by a number 2 Year 4 of factors. Window replacement Ventilation system has been selected as the first (balanced ERV system + phase because it is clear from exhaust) energy modeling that it provides the greatest number of comfort 3 Year 8 and energy benefits, although the Envelope 2: wall insulation & ventilation or exterior insulation airtightness phases could occur prior to window replacement. Decisions 4 Year 12 about phasing will be influenced Replace heating/cooling by the specifics of each building’s systems with VRF system systems, including their ages and ongoing maintenance costs. If 5 Year 16 both the window replacement Replace domestic hot and the exterior insulation occur water boiler with high prior to the ventilation upgrade, efficiency model there is a significant risk of developing moisture problems. 6 Anytime Since the current domestic hot Upgrade lighting to LED, water system relies on the steam upgrade elevators, install system boiler, it makes sense to energy efficient appliances

Figure 38: Energy Reductions by Retrofit Phase

99.44

88.1 82.8

55.6

45.6

kBTU/SF/YR 41.6 36.6

0 1 2 3 4 5 6 Existing Windows Ventilation Insulation VRF H&C DHW LED+Apps

The fully completed retrofit is estimated to reduce total building energy use by 63%, with more than 60% of those reductions the result of new exterior insulation and high-performance windows.

Pursuing Passive Retrofit Phasing be-exchange.org 39 benefits & costs

The benefits of a complete Passive House retrofit result in a radical transformation of the building, from improved comfort, air quality, and aesthetics, to more responsive heating and cooling systems, to far lower utility bills.

The building industry tends to poor thermal performance of view the individual elements of exterior walls and windows. For energy efficiency projects as instance, the subject building of distinct entities that must prove this study has no insulation within their worth in simple payback the exterior walls and includes terms without reliance on other very low performance windows. measures. This approach severely Standard windows pose major limits the ability of the industry challenges to interior comfort— to improve the building stock and in winter, standard glazing offers prepare for the future, and it has a cold radiant surface while poor a calamitous impact on efforts to installation and degraded seals at reduce carbon emissions. the operable elements produce Passive House benefits derive drafts and frequently incubate from the combined result of condensation which can lead several highly interconnected to the development of mold. In measures reliant on one another summer, standard windows offer to produce extremely comfortable limited protection from solar heat buildings that use limited energy. gain while remaining a source of No single measure in Passive air infiltration and condensation. House is significantly attractive The higher performance windows on its own, but together they required by Passive House transform the building. The contribute significantly to benefits achieved are similarly improved air quality and allow bundled: thermal comfort without residents to be comfortable sitting high air quality does not represent next to a window in any season. a successful reinvention of a Since the space immediately next building, but taken together they to a poorly performing window can reposition a building, in on the coldest or hottest days investment terms, from Class B, is typically unused, it could be or even C, to Class A. argued that installing Passive House windows increases usable Thermal Comfort: As stated square footage. Exterior wall earlier, the improvements in insulation also improves interior interior comfort are one of the comfort and reduces the threat primary advantages of pursing of condensation, though less Passive House certification. Most dramatically than installing standard buildings suffer from better windows. a host of issues that degrade Understanding the science interior comfort, chiefly the of thermal comfort is critical to

40 be-exchange.org Pursuing Passive Benefits & Costs Figure 39: Thermal Comfort and Interior Temperatures

Existing Passive House

Outside Outside 18° 36° 66° 18°

45° 65° 45° 63.4°

48° Inside 66° Inside Delta 23° 68° Delta 2° 68° ✕ ✓

Insulating the exterior and installing high-performance windows ensures that the inside surface temperature of the exterior walls remains warmer throughout winter and, most importantly, closer to the interior air temperature. Research indicates that comfort is significantly compromised when this difference is greater than 7 degrees F. We estimate the existing building suffers from a difference nearly 3x this figure.

understanding the importance 7 degrees F. Figure 39 illustrates of insulation, airtightness, and the difference between the air high-performance windows. The temperature and the interior difference between the interior surfaces of the exterior walls and air temperature and the surface windows in the existing building temperature of the exterior once the Passive House envelope walls and windows drives at measures are complete. least three major components of On a winter day, the existing interior comfort: drafts, radiant building produces highly temperature and condensation. uncomfortable conditions When the difference in these near the exterior walls, with temperatures is large enough a difference between air and the warm interior hits the cold surface temperatures of more surface, cools and then falls than 20 degrees, almost three toward the floor creating a times the recommended delta, dramatic internal draft—air certain to produce significant movement that occupants drafts and radiant chills for anyone experience as a chill, even if the near the walls or windows. Passive ambient air temperature remains House is a completely different constant. You may remember from story, with the exterior insulation high school physics that warm and high-performance windows objects radiate heat towards cold providing a comfortable interior ones, and this remains true if the that will not produce internal objects are humans and exterior drafts or radiant chills. Imagine walls. If the exterior walls and how differently you’d dress when windows are significantly colder leaving the house for the day if the than the ambient air temperature, temperature outside matched the humans feel chilled near the interior temperatures above. exterior walls and windows. If it is in the mid-40s outside, most Research by the Passive House of us would wear an insulated Institute12 indicates that these jacket; if it’s in the mid-60s, we’d draft and radiant temperature wear something light or no coat discomfort issues generally occur at all. An upgraded envelope when the difference between air offers a clear and dramatic impact and surface temperature exceeds on comfort.

Pursuing Passive Benefits & Costs be-exchange.org 41 A related element of comfort Energy Cost Savings: In addition in Passive House projects is the to the raw utility savings outlined steadiness of the temperature in Figure 40, the reduced energy within the spaces. In a typical use of Passive House certified building, the heating and buildings also significantly cooling systems cycle on and mitigates risk by insulating the off frequently as the envelope owners and tenants from utility loses or gains heat. Residents cost fluctuations. In the near feel these frequent changes in future it is likely that utilities will air temperature (and the drafts look to charge more for energy created) as discomfort. But the delivered in peak periods and that higher performing envelope of energy will be more expensive a Passive House project means than in prior years. The impact that the changes in interior of both factors is mitigated by temperature happen more slowly Passive House certified buildings. and less frequently, meaning the heating and cooling system is Net Costs: Figure 41 includes used less often and the residents conservative estimates of the experience a more balanced, costs of each phase of proposed comfortable interior environment. work. These figures include the costs to furnish and install Health: Air infiltration and all the required components of condensation are among the each phase, including all general primary vectors for poor indoor conditions such as scaffolding and air quality. The former can be protection, together with on site the source of moisture and staff. The following costs are also myriad pollutants (including included: carcinogens like PM 2.5) while the latter is the foundation of Insurance 4% interior mold growth. Additionally, Overhead 2% the balanced, highly filtered Fee 8% ventilation system in a Passive Contingency 10% House building provides ample amounts of fresh air. This The table includes costs for mixture of reduced pollutants each retrofit phase, if delivered and increased fresh air can separately, as well alternates provide a far healthier building for two of the phases, and the interior than typical. costs of business-as-usual (BAU)

Figure 40: Annual Energy Cost Savings by Phase

Electricity Gas kBTU/SF/YR kWh/YR $/YR* kBTU/SF/YR therms/YR $/YR** total ($) Existing Utility Costs 11 396429 $79,286 64.29 79077 $83,031 $162,316

Utility Cost Savings by Phases 1 Windows 0 0 $0 10.23 12583 $13,212 $13,212 2 Ventilation -0.68 -24507 $4,901 6.51 8007 $8,408 $3,506 3 Ext. Insul. 0.21 7568 $1,514 24.36 29963 $31,461 $32,975 4 VRF 0.82 29552 $5,910 7.13 8770 $9,208 $15,119 5 DHW 0.15 5406 $1,081 3.25 3998 $4,197 $5,279 6 Plugs/Appliances 1.94 69916 $13,983 0 0 $0 $13,983

Totals 2.44 $17,587 51.48 $66,486 $84,073

* Cost kWh $0.20 ** Cost therms $1.05

42 be-exchange.org Pursuing Passive Benefits & Costs Figure 41: Retrofit Construction Costs by Phase

Phase Est. Cost ($) Alternates BAU Costs Windows/Roof insulation $4,494,000 - -$652,000 Ventilation (balanced ERV + exhaust refurb) $1,447,000 - -$324,000 Exterior insulation + airtightness $2,528,000 -$1,150,000 Alt: Exterior rainscreen + airtightness $1,191,000 Install VRF system (remove steam/PTACS) $3,071,000 -$1,261,000 Alt: Install HP Packaged H/C units (remove steam/PTACS) -$1,054,000 Replace DHW boiler $250,000 - -$250,000

Total costs, phased $11,790,000 (A) General Conditions reduced (if single phase project) $1,655,000 (B) Total, alternates (net) $137,000 (C) Total offset costs $3,636,000 (D)

Total costs, single project $10,135,000 (A-B) Net costs, phased $8,154,000 (A-D) Net costs, single project $6,498,000 (A-B-D) + Alternates, single project $10,272,000 (A-B+C) + Alternates, multiple phases $11,928,000 (A+C) Optimal Project (net, future) $6,635,000 (A-B-D+C)

Phasing the retrofit delays the full benefits of the retrofit while adding $1.6M to the $10.1M cost of doing the work in a single phase. If the BAU costs of equipment upgrades are deducted, the net cost of the retrofit is $6.5M, less than 8% of the current market value of the building.

upgrades that the building might asset value, liens or other reasonably expect to perform obligations, tax subsidies enjoyed, over time. The sidebar on page rental revenue history, credit 44 outlines the scope of the score and credit history. Owners BAU items. will need to describe the full suite of benefits to lenders, from energy cost savings, to interior Financing comfort and air quality, to risk mitigation and improved asset Simple energy efficiency projects value. Opportunities for financing are typically evaluated by the building energy efficiency number of years required to pay retrofits include: back the expenditure from utility savings. But this is an insufficient Operating Budget/Reserves: lens through which to evaluate Before assessing outside financing a deep retrofit that transforms a needs, owners should carefully building in almost every capacity. analyze the ability of current Instead, we should evaluate these operating budgets to finance projects based on their impact on portions of an energy efficiency the total value of the building. retrofit, including consideration of At the same time, we should any reserves. identify mechanisms to connect the overall societal benefits of Construction/Equipment Loans: these projects to the costs borne Whether secured by the property by the individual building. (construction loan) or equipment, Prospects for financing a excellent credit is usually required project of this sort vary wildly due for these shorter term, project- to the great number of variables based loans with relatively high involved. These include, but interest. are not limited to, ownership structure, current debt service,

Pursuing Passive Benefits & Costs be-exchange.org 43 PACE Loans: Property Assessed many circles will be to compare Scope of BAU Upgrades Clean Energy (PACE) loans are these figures to far less costly Upgrade work that would be financed through a buildings equipment upgrades. But the required regardless of the retrofit. property tax assessment and project envisioned in this study is Estimates are in the ‘BAU Costs’ typically cover work related to not just an efficiency upgrade, it column in Figure 41. energy efficiency and renewable is a radical transformation of the energy projects. Longer term asset, improving the performance Phase 1 Windows/Roof Full roof replacement. Standard than standard equipment loans, and character of virtually every window replacement (Passive providers typically require the aspect of the property. House window units and Passive energy costs savings exceed the It would be ideal to point House level installation are more debt service on a monthly basis. to the costs of similar projects, expensive.) Although anticipated in the near but the lack of comparable Phase 2 Ventilation future, PACE loans are not currently transformations of existing Maintenance and repair costs of the available in New York City. buildings is one of the reasons existing system. this study was undertaken. Affordable Housing Loan The other primary means of Phase 3 Exterior Recladding Significant ongoing maintenance Programs: For rent regulated providing tenants with 21st costs of façade repair, including properties, the New York century performance is to build additional local law 11 compliance City Department of Housing new. New construction costs costs. Preservation and Development in New York City for high-rise (NYC HPD) offers subsidized loans apartment buildings currently Phase 4 VRF System 13 Replacement costs of the boiler and and grant programs to finance average $302 per square foot . the maintenance costs of the steam energy efficiency projects. NYC The retrofit described in this heating system. HPD also manages the J-51 tax report provides similar comfort benefit program, which provides and energy performance at less Phase 5 DHW Boiler tax abatements and exemptions to than one-third the cost. Heat exchanger replacement. offset building capital investments Ultimately, the appropriate in rent regulated properties. benchmark for a deep, holistic Some NYC HPD programs are retrofit of the type described also available to unregulated here might be asset value. The properties that enter into a costs of the optimal retrofit regulatory agreement. are roughly 12% of the current market value of the property. Mortgage Refinance: Proceeds New apartment buildings in the from mortgage refinancing are vicinity have an average sale cost a likely means of securing funds that is roughly twice that of the to perform the type of deep, subject building. It is clear that the holistic building transformations retrofit described here—featuring described in this study. a completely new exterior Some lenders offer interest skin, vastly improved interior rate reductions for projects conditions, and highly responsive, pursuing energy efficiency, or efficient systems—would deliver size supportable loans based an increase in market value several on planned energy savings. times greater than the costs. Pairing a mortgage refinance with a construction loan is also a common financing approach for capital improvements.

It is important to make appropriate comparisons when discussing projects of this scope, especially when they are not commonplace in our market. The total cost of the optimal retrofit described in the study is estimated to be $10,135,000, or roughly $82 per square foot, or $62,000 per unit (Figure 41). The temptation in

44 be-exchange.org Pursuing Passive Benefits & Costs conclusions

A substantial percentage of our building of significantly higher existing building stock must value that will allow our undergo deep, holistic retrofits community to meet its climate if we are going to meet our action goals. Inaction is not an climate action goals and avoid option. the most calamitous impacts New York City and State of global climate change. The are both currently working problem of climate change on programs that incentivize can seem overwhelming in deep retrofits of buildings and scale and complexity, but the demonstrate clear national responses required can be leadership on this issue. Chief broken into a series of small among these are the High actions. What must each city Performance Track of the do? Each building? What are NYC Retrofit Accelerator and the steps that building should NYSERDA’s RetrofitNY program take? Implementing the answers (see page 12). Many of the to these questions is the surest recommendations within this path to a sustainable future and report align with the mission the subject of this report. of these programs. Moving There are, of course, many forward, we will need to different pathways to producing incentivize the more effective highly efficient buildings. delivery of retrofitted systems, We’ve selected the Passive whether this means creating House pathway to inform this a strong market demand for report because of its focus on modular recladding systems comfortable, healthy spaces or ensuring that efficient and its strong track record of equipment such as the high delivering significant heating performance packaged heating and cooling energy savings. and cooling units discussed The costs are substantial, but earlier in this report are the benefits are extensive and available here. We will also need result in a radically transformed to identify mechanisms that

Pursuing Passive Conclusions be-exchange.org 45 connect the broader societal buildings, and commercial benefits of deep retrofits with properties. the costs to individual building owners. This might involve Modular Systems Research: property tax relief briefly The costs estimated here discussed above, or PACE assume current methods of programs, or some mixture of production and construction, these and other initiatives. processes that have been resistant to change while other sectors have advanced Path Forward productivity significantly. Additional research, perhaps Based on the various findings in concert with the RetrofitNY and lessons within these pages, program, is required to we recommend the following determine the feasibility of path forward to build on the creating modular retrofit work of this report, and further systems that might encapsulate explore both the feasibility of buildings of this type in a new deep retrofits and ways to scale envelope and perhaps include their implementation. heating, cooling and ventilation systems. Deep Retrofit Studies: Building on this foundational Finance and Policy Research: feasibility study, we recommend There currently is a limited quickly applying this analytical market for the type of extensive framework to multiple and holistic retrofit of an other building typologies to occupied building described determine the commonality here. Both policy-makers and of the findings and to provide real estate stakeholders should additional guidance for owners. develop a firm grasp on the These studies could provide financial and policy instruments less contextual narrative and that might directly incentivize process description, but no less such a market. technical information on the strategies required to meet our High Performance Systems climate action goals. Additional Research: This report identifies challenges that might be a specific product, available explored in these studies include in the EU and the UK, that would lot-line buildings, mixed-use significantly reduce the cost and

46 be-exchange.org Pursuing Passive Conclusions complexity of the deep retrofit. This study finds that buildings Further study should identify can definitely play a leading systems (such as air-to-water role in ensuring such a future. domestic hot water heat pumps) Now we to need to determine or products that are either the most effective means of available elsewhere or are on grasping this opportunity. the cusp of commercialization, that could significantly improve the feasibility and dramatically reduce the cost of these radical transformations of existing buildings.

Education and Training: Extensive education and technical training is required to enable high performance retrofits to move forward at scale. These activities should be directed not just towards architects, engineers and related consultants, but at building owners and managers, the finance sector, and virtually every category of professional that influences decisions about buildings and the way they use energy.

It is clear from our analysis that it is feasible to transform an occupied building of this type to meet the demands of our coming century, while providing a living environment of far higher quality than most of us currently enjoy. Our task is to ensure a sustainable, equitable future for our communities.

Pursuing Passive Conclusions be-exchange.org 47 acknowledgements

Contributors Disclaimer

Primary Author While every effort has been made Yetsuh Frank to contain correct information, Building Energy Exchange neither Building Energy Exchange nor the authors or project advisors Lead Technical Advisor makes any warranty, express or Lois Arena implied, or assumes any legal Steven Winter Associates responsibility for the accuracy, completeness, or usefulness Passive House Modeling of any information, apparatus, Jan Steiger product, or process disclosed, or Passive House Institute represents that its use would not infringe privately owned rights. Cost Estimating None of the parties involved in Greg Bauso the funding or the creation of Monadnock Construction this study assume any liability or responsibility to the user or Technology Support any third party for the accuracy, Sam McAfee completeness, or use or reliance Fentrend on any information contained Mike Woolsey in the report, or for any injuries, Swegon losses or damages arising from Ken Levenson such use or reliance. 475 Building Supply Reference herein to any Joe Fox specific commercial product, Mitsubishi process, or service by its trade name, trademark, manufacturer, Graphic Design or otherwise does not necessarily Brette Richmond constitute or imply its endorsement, recommendation, Editing or favoring by Building Energy Angela Riechers Exchange. The views and opinions of authors expressed herein do not necessarily reflect those of This report made possible by the Building Energy Exchange support from: Board or Advisory Groups. As a condition of use, the user pledges not to sue and agrees to waive and release Building Energy Exchange, its members, its funders, and its contractors from any and all claims, demands, and causes of action for any injuries, losses or damages that the user may now or hereafter ©Building Energy Exchange have a right to assert against such All Rights Reserved parties as a result of the use of, or October 2018 reliance on, the report. be-exchange.org

48 be-exchange.org Pursuing Passive Acknowledgements end notes

1 https://www1.nyc.gov/assets/sustainability/downloads/pdf/ publications/New%20York%20City's%20Roadmap%20to%20 80%20x%2050_Final.pdf

2 http://www.nyc.gov/html/builttolast/assets/downloads/pdf/ OneCity.pdf

3 Urban Green Expo Keynote, September 23, 2009

4 nyc.gov/onenyc

5 https://www.ucsusa.org/global-warming/science-and-impacts/ science/each-countrys-share-of-co2.html#.W65TQBNJFTY

6 http://www.nyc.gov/html/planyc/downloads/pdf/publications/ full_report_2007.pdf

7 http://www.nyc.gov/html/gbee/html/plan/plan.shtml

8 nyc.gov/onenyc

9 https://www1.nyc.gov/assets/sustainability/downloads/pdf/ publications/TWGreport_04212016.pdf

10 https://passivehouse.com/02_informations/01_ whatisapassivehouse/01_whatisapassivehouse.htm

11 https://passipedia.org/operation/operation_and_experience/ measurement_results/energy_use_measurement_results

12 https://passiv.de/downloads/05_fenster_optimierung- baukoerperanschluss.pdf

13 https://therealdeal.com/2018/05/15/surprise-nyc-remains-most- expensive-place-to-build-in-the-world-report/

Photo Credits

Inside Cover Yetsuh Frank 1 Yetsuh Frank 5 Yetsuh Frank 8 Field Conditions & Pavel Bendov 17 GUTEX 19 Shildan 20 Schuco 24 Mitsubishi 35 Swegon

Pursuing Passive End Notes be-exchange.org 49 BEEx: the building energy exchange connects New York City real estate and design communities to energy and lighting efficiency solutions through exhibitions, education, technology demonstrations, and research. We identify opportunities, navigate barriers to adoption, broker relationships, and showcase best practices at our resource center in Manhattan.

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