Passive House and High Performance Housing: A Report to the UMORE Park Management Team
Submitted by John Carmody Dan Handeen
Center for Sustainable Building Research College of Design University of Minnesota
Mar. 8, 2012
Passive House and High-Performance Housing
Contents 1 Introduction 3 Part 1: The Passive House Concept 3 What is a Passive House? 4 History 4 Origin of Performance Requirements 6 Critiques of the PassiveHouse Software 7 Passive House Certification Strategies in Minnesota 11 Advantages of Passive House 12 Challenges to Building Passive Houses in Minnesota 19 Part 2: Results and Conclusions 19 Results 24 Life Cycle Cost Comparison 34 Conclusions 37 Part 3: Building Survey and Case Studies 38 Certified Passive Houses 38 Waldsee BioHaus 38 The NewenHouse Prototype I 39 Konkol Residence 39 Isabella EcoHouse 40 Non-Certified Passive Houses 40 Bagley Classroom 40 Skyline House 41 Esko Farmhouse 41 Synergy, TE Studio 42 The Holm Retreat 42 The Erickson Home 43 High Performance Houses 43 The Walker House 43 Stemwell House 44 Case Study I: Konkol Residence (TE Studio) 46 Case Study II: Synergy high-performance home (TE Studio) 48 Case Study III: NewenHouse Prototype I (Coulson Architect) 50 Case Study IV: Isabella EcoHome Experiment Station (Compass Rose) 52 Web Resource List
College of Design Passive House and High-Performance Housing
ACKNOWLEDGEMENTS
The authors are grateful for the opportunity to conduct this study on Passive House and other high perfor- mance housing approaches that might be appropriate in meeting the goals of the University of Minnesota’s UMORE development. We appreciate the direction, support, and feedback of the UMORE Management team including Charles Muscoplat, Carla Carlson, Larry Laukka, Tom LaSalle, Ken Larson, Steven Lott, Julie Boudurtha, Lorri Chapman, and Allie Klynderud.
The report has required the assistance of many people in collecting case study information and providing insights into energy efficient construction in Minnesota. We would like to thank: Tim Eian, TE Studio Stephan Tanner, INTEP Philipp Gross, TE Studio Edwin Dehler-Seter, Concordia Language Villages Mike LeBeau, Conservation Technologies Rachel Wagner, Wagner Zaun Architects Carly Coulson, Coulson Architect Sonya Newenhouse, Madison Environmental Group Malini Srivastava, NDSU Nancy Schultz, Compass Rose, Inc. Ray Pruban, Amaris Homes Brad Richardson, Christian Homes Ed VonThoma, Building Knowledge
The report was also enhanced by discussions with other building researchers at the University of Minnesota including Pat Huelman, Louise Goldberg, Garrett Mosiman, and Rolf Jacobson.
Cover images, clockwise from top left: Isabella EcoHome Research Station, Compass Rose Design; NewenHouse Prototype, Coulson Architect; U of M Duluth Bagley Classroom, Salmela Architects; The Konkol House, TE Studio.
College of Design Passive House and High-Performance Housing
Introduction Purpose and scope This study grew out of a desire to explore innovative The report consists of three sections. Part 1 provides approaches to meeting the aspirational goals of an overview of the principles and issues inherent the UMORE Park development for a low-energy, to Passive House construction, and investigates low-impact sustainable community. During a study some of the complexities, challenges, and benefits trip of sustainable community design in Europe, of a Passive House approach to construction. The the Passive House concept was introduced to the second part includes the results and conclusions. UMORE management team. This report is intended Part 3 comprises a survey of Passive House build- to further explore the Passive House concept as ings in Minnesota, in addition to some other high- it might be applied to the UMORE development performance buildings for comparison purposes. project in Minnesota. The report also examines This is provided in order to establish a spectrum of examples of advanced energy efficient construction construction types related to energy efficiency and now occurring in Minnesota so that the Passive energy performance. Four case studies are docu- House concept can be put into a larger context of mented in greater depth. high performance housing options. Much of the information in the report is based on interviews and data collection from Passive House and other advanced energy efficient homes on Minnesota.
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Part 1: The Passive House Concept The Passive House Certification Criteria What is a Passive House? For a building to be certified as a Passive House, it must meet the following criteria: In its most basic definition, a Passive House (PH) Heating energy consumption ≤ 4.7 kBtu/ft2/yr. is a building for which thermal comfort (ISO Cooling energy consumption ≤ 4.7 kBtu/ft2/yr. 7730) can be achieved solely by post-heating or Primary energy consumption ≤ 38.1 kBtu/ft2/yr. post-cooling the fresh air mass required to achieve Airtightness ≤ .6 ACH@50pa sufficient indoor air quality conditions – without the Also recommended but not required: need for additional recirculation of air. Design heating load ≤ 10 W/m2 Window heat transfer coefficient ≤ U-0.14 In execution, a Passive House is a very well- insulated, virtually air-tight building that is primarily heated by passive solar gain and internal heat 3) The airtightness of the building must be no more sources such as occupants and electrical equipment. than 0.6 air changes per hour at 50 pascals pressure, Energy losses are minimized. Any remaining heat as measured by a blower door test. demand is provided by a very small source. Avoid- ance of heat gain through shading and window The Passive House standards also recommend, but orientation also helps to minimize any cooling load. do not require, the following: 1) A maximum designed heating load for the build- A certified Passive House refers to a building or ing of 10W/m2 (3.4 Btu/hr/ft2).* structure that has met the certification criteria set 2) Windows with a maximum U-value of 0.14. forth by the Passive House Institute (PHI) in Darm- stadt, Germany. Passive House experts and practitioners add multiple 1) The building must use no more than 4.746 kBtu/ aspects of what the Passive House approach implies. ft2 per year for heating or cooling, as calculated Simplicity, durability, low-maintenance, and com- using the Passive House software. fortable are all adjectives used to describe a Passive 2) The building must use no more than 38.1 kBtu/ House building. “Passive House is economically, ft2 per year in primary (source) energy for all energy environmentally, and socially responsible and per- consumed, including heating, cooling, and electric manently feasible. [It provides] quality of life at low loads, as calculated using the Passive House soft- cost and low impact to the planet,” says Tim Eian, a ware. Passive House architect based in Minneapolis. *This is the estimated maximum amount of heat that can safely and effectively be supplied via ventilation air. Heating demands in excess of 10W/m2 will require additional heat sources.
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Origin of Performance Requirements Heating/Cooling Energy The 4.75 kBtu/ft2/yr (15kWh/m2/yr) number is set to be the optimum amount of energy for a German home to be able to heat itself without requiring a typical furnace or heating system. The number is based on analysis of economic data, and results in a roughly 80%-90% reduction in overall energy usage compared to a typical home.
Primary Energy A schematic description of Passive House design elements. It was quickly noticed that the heating needs of the building could be met by very inefficient means, such as incandescent light bulbs. This defeated the History underlying point of the heating standard, and did not The Passive House concept originated in Darmstadt, address the greater systemic problems due to electri- Germany under the name PassivHaus. Dr. Wolfgang cal power generation. Through analysis of global Feist, a physics professor, was researching high-per- warming projections and carbon emissions, the Pas- formance homes. Drawing from superinsulation and sivHaus Institut proposed that the optimal amount passive solar design techniques that originated in the of primary energy (that is energy generated off-site) US and Canada, he and his colleagues proposed the consumed by all operations in the building, includ- idea that if the insulation levels were high enough, ing heating, cooling, and electrical processes, should the need for a typical furnace and air distribution system (and its associated cost) could be eliminated. The money that would have been spent on a furnace could instead be put toward greater insulation and airtightness measures, and thus be cost-competitive with conventional construction. This initial theory has been proven over the course of about 30 years by the careful analysis of over 100 European Passive Houses by the PassivHaus Institut or PHI.
The first PassivHaus. Constructed near Darmstadt, Germany in 1991.
4 College of Design Passive House and High-Performance Housing be less than 120 kWh/m2 (31.8 kBtu/ft2) per year, as sure performance in relation to a reference building. calculated using the Passive House software. This figure is based on a Central European energy Calculation and Software mix. Because of inefficiencies in heat production To aid in the design of such a high-performance and electrical distribution, it requires roughly 2.7 building, Dr. Feist and PHI developed a tool called units of source energy to provide one unit of energy the Passive House Planning Package, or PHPP. It for use at the building. In the US, however, there is is essentially an intricate Excel spreadsheet that even greater inefficiency, estimated at a factor of 3.1 calculates the energy flows of a particular building source units to one site unit. Electrical fuel sources based on the user’s entries. The spreadsheet requires and grid efficiencies vary widely, but if the PH entries relating to very specific aspects of the build- primary energy standard was adjusted to account for ing, such as window frame U-values and appliance average US electrical grid distribution, it would be efficiency ratings. The PHPP calculations include closer to 105 kWh/m2 (27.7 kBtu/ft2) per year. the effects of occupancy, solar orientation, shad- ing, and location-specific climate variations based Airtightness on climate data sets. Additionally, it calculates the To meet the heating or cooling energy requirement energy lost through thermal bridging in the user- of the Passive House, control of the indoor environ- defined assemblies. By comparing the results of the ment is necessary and an airtight structure ensures PHPP with actual measured data from constructed this control. An airtightness level of 0.3ACH50 Passive Houses, the developers have been able to is about as low as economically reasonable for a adjust and verify the accuracy of the PHPP to a very timber structure, while humidity levels and building close percentage. durability are adversely affected at airtightness lev- els above 1.0ACH50. The Passive House standard One of the strengths of the PHPP is that it places of 0.6ACH50 strikes a balance between economic particular emphasis on the heat losses created by feasibility and adequate hygrothermal control. the thermal bridging of structural components. The effectiveness of different types of thermal envelope Clear Benchmarks for Rating and Comparison assemblies has been well researched. The weakness The Passive House standards are unique in that they lies in the connections where materials meet. “The set specific, predictable and measurable energy per- big things have been figured out. Now it’s down to formance targets. This sets a standard against which the details,” according to Passive House designer any building can be measured. This is in contrast to and architect Rachel Wagner. programs such as the US Department of Energy’s Energy Star program or the US Green Building Unlike some other energy modeling software that Council’s LEED for Homes program, which mea- calculates results in a “black box,” the PHPP is
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relatively transparent. Because it is Excel-based, the simplified calculation techniques are theoretically user is able to directly investigate the ways in which problematic in extreme climates such as Minnesota. the results are calculated. Although somewhat daunt- However, the Passive House experts concluded that ing at first, the PHPP is relatively easy to use. The the insulation levels of a Passive House are so high most intimidating aspects are the number and the that the temperatures and energy demands do not specificity of inputs that it requires for accurate cal- fluctuate as drastically as in a typical home, so hour- culation. Regardless of whether or not one is seek- by-hour calculations are not necessary. ing Passive House certification, the PHPP provides a robust and thorough means of checking the energy Cooling Energy Requirements balance of a high-performance building, and shows The PHPP was validated by observing the behavior the impacts of changes in design or components. of buildings in Central Europe. Because the climate there is milder than the Upper Midwest of the US, Rachel Wagner, says that her office will initially there is some concern over whether or not the PHPP model a client’s home to the 2006 IECC standard, adequately addresses latent heat in Minnesota’s hot, which is very similar to Minnesota’s current build- humid summer. ing code. Then they enter the specifications of the energy efficient home they actually plan to build. Data Entry When the energy calculations of the “improved” Because of the popularity of the Passive House house are shared with the clients, “They never say movement in Europe, many companies provide data ‘no’.” for their products that can be easily entered into the PHPP. Additionally, there are some products, such Critiques of the PHPP Software as windows or heat recovery ventilators, that are Some building scientists believe the software to be certified “Passive House” components. Only a few overly simplistic. Unlike most energy-modeling American manufacturers currently provide the same programs, the PHPP calculates the energy balance of type of data or receive such certification, so enter- the building as a whole, not as separate conditioned ing component data in the PHPP can be somewhat zones. This could potentially affect the thermal com- difficult. The default performance numbers in the fort of individual rooms as heat distribution may not PHPP are particularly harsh against components that be adequate or ideal. are not PH-certified. For instance, the efficiency of a non-PH HRV is entered at 12% less than it is rated. Another critique is that the PHPP calculates monthly energy balances instead of performing time-resolved Need for User Accuracy simulations. While not a problem in relatively mild Because of the intricacy and interrelated nature of and stable climates such as central Europe, these the PHPP, each entry field needs to be understood
6 College of Design Passive House and High-Performance Housing and correctly filled. Omitted or incorrect numbers can have significant effects on Impacts of Building Geometry the end results of the spreadsheet. on Volume and Surface Area
Area Calculation Another common issue with the PHPP is how floor areas are calculated. While the standard area measurement in the US is based on exterior wall measurements (as per ASHRAE), the PHPP uses Treated Floor Area (TFA), which is similar to the 2 Finished Floor Area or conditioned space Floor area - 1200 ft Volume - 10800 ft3 area.A TF refers to the area inside the ex- Surface area - 3000 ft2 Floor area - 1200 ft2 terior walls, minus interior walls and stair- Volume - 13800 ft3 cases as well as columns over a certain Surface area - 5277 ft2 size; and 60% of secondary spaces such as storage, mechanical rooms and base- Technologies in Duluth, says that it is much more ments. While this may not be a difficult concept, the efficient and cost-effective if you “start with the problem arises when values are given per unit area. [energy performance] goal and design to that, rather Cost per square foot or energy use per square foot than start with a design and force it to meet a goal.” could vary greatly depending on which type of area is used, with the ASHRAE technique giving a result Simple Shapes with up to 30% lower costs and greater efficiency. Because of the relationship between surface area and volume, simple geometry makes for a more efficient Passive House Certification Strategies in building and is rewarded in the PHPP. Fewer bump- Minnesota outs, dormers, and wings means less surface area Since Passive House is a set of performance criteria, per unit of conditioned floor area. Simpler geometry and not a prescriptive method, there are many ways also implies fewer structural connections and less to work toward meeting the specific performance possibility for thermal bridging. And because they criteria. There are a number of common strategies, have fewer edges and joints, it is also easier to however. The first one, and probably the most achieve the airtightness standard with simple-shaped important, is to set the performance criteria as the buildings. goal at the beginning of the process. Passive House energy consultant Mike LeBeau of Conservation
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Window section comparison
Standard Energy Star Window Typical Passive House Window U-0.35 U-0.17
Insulation To meet the low levels of allowable heating energy, Regardless of what type of insulation or wall as- high amounts of insulation are crucial in Minnesota. sembly is utilized, it is important to make sure that Insulation values for a Minnesota Passive House moisture will not remain in the wall. walls are typically about three times as much as is called for by Minnesota Building Code. High insula- High-performance Windows tion values can be achieved in many different ways Because of the amount of sunlight that we receive in and with different materials. Many designers prefer Minnesota, windows can provide an annual net gain a low-tech approach that uses double stud walls and in heating energy. However, windows do not gener- densely-packed cellulose insulation. The materials ally insulate as well as opaque walls. For this reason, are relatively inert, and they have low environmental high-performance triple- or quadruple-glazed win- impact along with being relatively inexpensive. dows with a low U-value and tightly-sealed frames Other designers prefer insulated concrete forms for are used for Passive House construction. Windows their ease of construction, durability, and waterproof are also “tuned” based on their solar orientation, construction. A high-tech route is to use vacuum with windows that have higher solar heat gain coef- panels. These panels insulate very well and enable ficients placed on the south side of the building. thinner walls, but they are not forgiving in construc- tion.
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Comparison of Wall, Roof, and Slab Sections for Three Building Energy Standards
Typical MN Code Advanced Passive House
Wall R-19 R-35
R-58 Roof
R-38 R-60 R-77
R-10 R-10 Slab
R-44 Graphic by TE Studios Graphic by
Backup Heat For most of the year, passive solar heating is ad- simplicity, different types of electric heaters are fre- equate. However, during periods of extreme cold, a quently used, including baseboard, radiant panel, and backup heat source is required and it is unrealistic to radiant floor. Air-to-air heat pumps are also frequently distribute all necessary heat through the ventilation used. Another backup option is a wood stove, which system in Minnesota. Because of their ease and can provide security if all other utilities fail.
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The Heat Recovery Ventilator
Passive Solar Design A fundamental Passive House strategy is to use the sun to heat the building. This is achieved by orienting the building to maximize the opportunity Exterior shading device on the Biohaus near Bemidji, MN for passive solar gain through windows into the conditioned space. Minnesota’s climate and amount of sunshine can provide a net heat gain with proper solar-oriented design and window placement. Exterior Shading Devices Passive Houses rely on solar heat gain through Heat-Recovery Ventilation windows. While large south facing windows ensure To achieve the energy performance and airtightness comfort during the winter months, they can let in in a Minnesota Passive House, a heat recovery uncomfortable amounts of light and heat in the ventilator, or HRV, is an almost necessary compo- summer and “swing seasons” of spring and fall. To nent. These devices draw in fresh air from outside counter unwanted solar gain, numerous types of and exhaust stale air from inside. While doing so, exterior shading devices are used. These can include they transfer the heat from the exhaust air to the active devices, such as awnings and roll-up shades, incoming air and thereby save heating energy. Heat and passive elements, such as balconies and roof recovery ventilation can provide greater occupant overhangs. Depending on where the window is comfort and support occupant health via increased placed, even the wall thickness can provide shading. fresh air levels over a typically-ventilated building.
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Passive House Certification in the United States Advantages of Passive House The Passive House Institute in the United States Decreased Energy Costs (PHIUS) has begun training professionals in Passive The Passive House performance criteria are House design and use of the PHPP, and certifying primarily concerned with low energy usage. If this buildings as official Passive Houses. They are decreased energy use is translated to dollars, a clear acutely aware of the challenges to achieving certi- benefit of building a Passive House is decreased fication given the range of climates in the United operating energy costs. States (such as Minnesota), and have begun investi- gation into creating an alternate set of performance Energy Security criteria that are more locally appropriate. While this Requiring less energy to heat, cool, and enjoy your has been met with resistance by PHI in Germany, house means less fuel need be consumed. Although it seems to be the logical next step in spreading the the US has large reserves of coal and natural gas, standard to other more demanding climates. and good access to oil, the fluctuations and volatil- ity of the fuel markets are unpredictable, and less Some other northern European countries have reliance upon them provides a measure of security. modified the targets or devised their own targets to be more attainable. For example, Sweden has Passive Survivability slightly more lenient targets for their northern Passive Houses can be designed to maintain oc- projects compared to their southern projects. France cupant comfort and building function if utilities are and Norway as well have devised their own sets of unavailable for some reason. Wagner says about her performance targets to be more location-specific. If projects: “If the propane runs out or the electrical the Passive House energy use targets are modified grid is cut off, the health and well-being of the to reflect the specific climates in which the project occupants and the systems within the building are is built, it may increase the number of projects that not threatened.” attain certification. Occupant Health It should be noted that one can still design and The underlying premise of Passive House is that all certify a Passive House building without taking heating can be distributed using only the ventilation the training, and buildings can be certified by any air. The ventilation is intended to be an assurance recognized Passive House affiliate around the world, of good air quality inside the home. Most existing not just those in the country where the building homes and many new ones simply recirculate air resides. within the building, adding little fresh air. Older homes that use radiators often have no ventilation system, and thus no fresh air intake. Passive Houses
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are designed to have higher indoor air quality hundred years. The use of higher-quality compo- than many existing homes because of increased nents implies less maintenance or replacement over ventilation levels. It should be noted, however, that time, resulting in reduced maintenance expenditures. building a very airtight house in Europe has lower air quality risks since standards regarding VOC and Brand Recognition other pollutant emissions from materials are more Despite the skepticism, confusion, and excitement stringent than in the US. If a Passive House is built over the Passive House concept, it has quickly is the US without these standards, care should be become the standard by which high-performance taken to select materials with low-VOC emissions to building is measured. The E.U. has mandated that ensure a non-toxic indoor environment. all new single-family homes shall be Passive House compliant by 2020. The term Passive House was Simplicity relatively unheard of three years ago, but has gained By replacing the typical furnace and its associated popularity and recognition -- and it is regarded as a ductwork with simpler systems such as an HRV challenging standard to meet. If one builds a Passive with electric backup, the complexity of the heating House in Minnesota, it is a remarkable achievement. system can be reduced. A number of homeowners have been able to install their own heating systems: Accountability and Ease of Use Instead of bending metal for ductwork, running The Passive House approach provides a proven tool gas lines, and installing a large furnace, the HVAC and proven method. If projects are certified accord- systems consisted of a single box with “plug-and- ing to the Passive House standard, the designers play” distribution ductwork, similar to vacuum and builders are held accountable to meeting the cleaner hose. It requires drilling holes, running the stringent criteria. The PHPP provides a coherent ducts to the registers, and plugging them in. and comprehensive means of guiding and testing throughout the design process. A simpler system also implies less noise, less energy consumption, and fewer components to replace over Challenges to Building Passive Houses time. in Minnesota Passive House sets a standard for energy use - a very Durability aggressive standard. Passive Houses have been built In keeping with a basic tenet of sustainability, in Minnesota, and are performing beyond expecta- Passive Houses are intended to be long-lasting tions. The concept has been proven and it is known structures. Because of the careful analysis of enve- to be feasible, but it does not come without some lope profiles typically undertaken in Passive House challenges. design, the structures should last more than one
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Initial Construction Costs While the costs associated with the construction utility rates, construction methods, and access to of Passive Houses in Minnesota vary from project high-performance building components. to project, there will always be increased cost compared to conventional construction. The higher- Availability of Components performing components, such as windows, doors, One obstacle to the construction of Passive House and appliances, coupled with the increase in enve- buildings in Minnesota is the lack of access to lope materials and the labor needed to install them, crucial high-performance building components. will generally lead to a greater first cost. “You don’t While European manufacturers and consumers have have to bring the windows from Germany,” says embraced high-efficiency products, the American Wagner, “but the windows are going to be expensive market is in the early phases of developing high- wherever you go. You restrict options when you performance components. However, according to need such high performance - but you do need that Rachel Wagner, the lack of technologies is “not as level of performance.” big an obstacle as it is being made out to be.” LeB- eau adds that “We have good windows, and we have Some estimates for building a single-family Passive the beginning of good mechanical systems.” While House come in as low as 3% over a comparable there are a handful of American manufacturers “code” home, but are more generally assumed building high-performance windows, for example, to be in the range of 10-20% higher. Even when certified Passive House windows are currently only measured against the anticipated lower utility costs available from Europe. However, one Wisconsin- over the life of the building, the up-front costs are a based manufacturer and a Colorado-based manu- significant deciding factor, and generally the most facturer are slated to start producing PH-certified influential one. However, it should be noted that windows in the near future, and Optiwin, a German many construction costs are associated with finishes, PH-certified window company, is considering US- and not related to energy performance. Thus, esti- based fabrication. mates and final construction costs are highly related to client or owner preferences and can vary widely. Other high-technology approaches such as vacuum panels and phase change materials have very little The Passive House performance standard is based market presence in the United States, although one on Central European cost effectiveness studies, Minnesota manufacturer is producing phase change and the cost of increased insulation and higher- materials for integration into multiple applications. performing components is justified using European Product integration and market acceptance of these construction and utility cost estimates. This reason- technologies remains to be seen. ing may not be applicable or relevant to other areas of the world depending on local resources, climate,
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Finely-tuned Design When the building energy use is so low, reducing Another challenge to building Passive House in any heat loss becomes increasingly important, and Minnesota is finding building professionals that commonly overlooked weaknesses such as thermal understand the subtleties and particularities of build- bridging need to be addressed. Successful Passive ing a Passive House. According to Norbert Klebl, a House design requires structural engineers who Passive House developer in Colorado, “The biggest understand how certain structural conditions can challenge for high performance affordable home compromise thermal integrity and will instead builders is to find competent and imaginative sub- design details to avoid them. contractors.“ The idea that heating can be distributed solely by the ventilation system is not common and Finally, the actual construction of the building is requires a deep understanding of the interactions be- the most important aspect of performance. Even the tween the heating, ventilation, and energy systems in best-designed structure will fail if the builder does a building. Many engineers will over-design systems not understand the plans. The airtightness require- to avoid risk of insufficient performance. While this ment in Passive House creates the need for excep- approach generally guarantees the desired thermal tional attention to detail on the part of the builder. outcomes, it can also result in energy consumption Passive House designer Rachel Wagner commented that far exceeds the Passive House standards. On the that one of her projects did not attain Passive House other hand, an oversimplification of the mechanical certification only because the blower door test came system can lead to thermal comfort issues. in 0.1ACH50 above the allowable limit. The home builder learned from that experience and the next Seemingly insignificant loads such as pumps and PH house they built came in 30% under the limit. compressors can require large amounts of electricity. These types of loads are not typically considered in Beside the airtightness consideration, there is the an HVAC design, but can have detrimental effects simple matter of quality construction. In an ironic against the pursuit of PH certification. twist regarding high-performance buildings, energy consultant Mike LeBeau says he has seen many To be successful, a Passive House design requires more building failures due to rainwater intrusion a finely-tuned system that responds uniquely to than due to airtightness issues: “People worry way the needs of the house within the limited amount more about perm ratings... than they do [about] of energy available. HVAC professionals need to window flashing.” design specifically to the task at hand, and work with precision and creativity to match the systems to the building and the PH energy use targets.
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Architectural Differences that permit such low energy consumption are gener- The architectural implications that result from Pas- ally quite thick, which results in walls from 16 to 24 sive House design could potentially dissuade buyers inches thick. This is considerably different than the or clients from wanting to pursue it. The need for standard 8-inch-thick residential wall with which solar heat gain makes it necessary to have larger most Minnesotans are familiar. windows on the south side of the house. In contrast, the north side of the house will ideally have very Design Conflicts few, if any, windows in order to minimize heat loss. Occasionally, there are conflicts between desired This may be incompatible with certain architectural outcomes. One example could be the desire for trees styles, and may be different in appearance than a in the nearby landscape versus the need to optimize “normal” Midwestern home. However, any distribu- solar gain. Depending on the local conditions, it may tion of windows is theoretically possible if their be necessary for the trees to be trimmed or removed. compromised thermal performance is mitigated by Similarly, a desired view from inside the house may other means. suggest that the main windows should look to the north, rather than the south, where they would be According to Duluth-based Architect Carly Coulson, most suitable from an energy perspective. However, a Passive House typically has more glass than a carefully considered design by qualified and knowl- traditional-looking home. She uses different clad- edgable professionals can resolve these challenges. ding treatments and architectural elements such as pergolas to break up the appearance. The window Moisture and Durability units themselves are an additional consideration Even though the Passive House concept has proven since the windows in a Passive House are usually effective in a number of Minnesota buildings, the casement type, rather than double hung, because long-term health impacts and durability of some of of improved air sealing capabilities. The mullions these structures is unknown. The concern lies with often seen in traditional windows can also decrease Minnesota’s hot, humid summers. Typical construc- thermal performance. tion has enough air and heat flow through the wall to “dry out” any humidity that may have entered. In Because of the relationships of surface to volume, a Passive House wall, there is very little heat energy Passive House certification is easier to attain with to carry moisture out. The effect may be that a simpler geometry. At a minimum, this optimization Passive House’s high insulation levels are very safe of surface area can lead to simple gabled house and effective in the cold, dry winter, but could retain forms with no articulations of the exterior walls. harmful levels of moisture in the summer. Further At its geometric extreme, this could mean a cube- research and long term monitoring is required to shaped building. Additionally, the insulation levels adequately address this issue.
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Many Americans are disinclined toward having With regard to the effect of humidity on the wall limits imposed on their living spaces, and although structure, the quality of construction is crucial. they may be concerned about how much money they The danger of harmful moisture accumulation is spend, they do not want to be told how to spend it. much greater from poor airsealing rather than from Passive House sets a limit on energy use that some diffuse vapor flow through the assembly. Because people may find arbitrary or unnecessary. Equivalent Passive Houses are generally more airtight, they to living in a typical house or driving a vehicle, per- are potentially less prone to moisture problems. sonal habits and priorities have a significant impact LeBeau is concerned that there could be a high on energy use and whether or not the performance degree of failure in US Passive Houses if basic criteria are met. building science and quality construction principles are not heeded: “Optimism and excitement [about It is commonly perceived that occupants of energy- the Passive House concept] make it seem like these efficient buildings will be subject to uncomfortable buildings are immune to forces of nature.” temperatures and unable to use “regular” appliances. However, Passive Houses address these issues with One way to address this issue is the application of appropriate technologies to ensure user comfort. hygrothermically symmetric building assemblies The default indoor design temperature for the PHPP such as Insulated Concrete Forms (ICF’s) and is 20ºC, or 68ºF, and can be adjusted by the user if Structural Insulated Panels (SIP’s). These wall types desired. It is then up to the designer to assemble a have the vapor barrier in the thermal middle of the thermal envelope and HVAC system that meets the wall and allow any moisture to dry toward both the design criteria. Similarly, the electrical use is capped inside and outside of the wall. An additional security at a certain figure depending on the size of the home. of ICF walls is that they contain biologically inert It is up to the designer and homeowners to outfit the materials like foam and concrete, which do not building with energy efficient appliances that meet promote bacterial or fungal growth. their lifestyle needs within that energy budget.
Public Perceptions In the end, a Passive House is simply a building The energy use limits put forth by Passive House are that has been designed to perform to certain set of quite aggressive. An 80-90% reduction in home en- criteria--How the occupants decide to live in it is ergy use can be seen as nearly impossible to achieve entirely up to them. If they decide to exceed the without sacrificing comfort, style, and familiarity. It modeled electrical use or turn up the thermostat, the is also viewed as prohibitively expensive, especially building does not prohibit them from doing so. in an extreme climate such as Minnesota’s.
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Integration with Other Building Programs and still be achieved while meeting the code require- Regulations ments, the issues that these particular codes are The Passive House standard focuses on reducing meant to address are not relevant when one builds energy use, and thus indirectly addresses greenhouse Passive House type construction. gas emissions. It does not address site, water, materials, and other sustainability issues. However, by combining Passive House with other criteria such as LEED or the Living Building Challenge, one can address a broader scope of sustainable design. Conflicts may arise between different building programs, however.
Salmela Architect designed the high-performance Bagley Classroom Building on the Duluth campus of the University of Minnesota. Carly Coulson was the project architect for the building, which is certified LEED Platinum and is seeking Passive House certification. As Coulson applied those two standards to the building, she noticed occasional incompatibilities. For instance, LEED offers credits for reflective or high-albedo roof materials to avoid urban heat island effects. However, an optimized Passive House design would suggest a solar absorp- tive material in order to reduce the heating load of the building. Another example is that LEED recommends ventilation rates at 30% beyond the code requirement. Heating and cooling this extra ventilation air requires energy that could make PH compliance difficult.
Passive House architect Tim Eian also notes a few specific code issues related to radon mitigation and plumbing venting that conflict with the Passive House design approach. While PH certification can
College of Design 17 Passive House and High-Performance Housing
18 College of Design Passive House and High-Performance Housing
Part 2: Results and Conclusions
The purpose of this study is to determine the current examples of community scale Passive House devel- status and viability of the Passive House concept in opments, market issues, and conclusions. Minnesota and to answer questions about its ap- plicability at UMORE Park. Case studies and inter- Results views with designers and other experts are the main Overall Viability and Performance of Passive sources of information to answer these questions. Houses in Minnesota This section includes the cost and performance If UMORE is to meet One Planet goals for carbon results that were compiled on case study houses and energy, Passive House design is one viable as well as a discussion of some key topics such as approach that is being successfully applied in the impact of Passive House design on planning, Minnesota. Several examples of certified and non-
The BioHaus at the Concordia German Language Village near Bemidji, MN. Designed by Stephan Tanner, the BioHaus was the first certified Passive House building in the US.
College of Design 19 Passive House and High-Performance Housing
certified but highly efficient houses have been built to the Passive House standard. Examples of these in Minnesota and Wisconsin. Many of these houses are included in the analysis for comparison of costs are designed to use 70%-80% less energy than a and performance. In Part 3 of the report, a survey of typical house built to code. This would be equivalent several Passive House and highly efficient projects to a HERS rating of 20-30 (where 0 is no energy use in Minnesota and Wisconsin are described. Data and 100 is a typical code building). from four of the case study houses are presented in detail. For some of the projects in the survey, The Passive House concept has been proven in costs were not available. The results in this section Minnesota for over five years at the BioHaus at the are drawn from this collection of certified Passive Concordia German Language Village near Bemidji, House and highly efficient projects. and it is currently exceeding the PH performance criteria by 10%-15% in climate zone 7. Passive Initial Costs for Passive House and Other High House seeks the same sort of reduced environmental Performance Projects impacts as programs such as the 2000-Watt society, Table 1 shows nine projects—five with actual con- and the Swiss Minergie standard, but also provides a struction costs and three with estimates for projects design tool to achieve it. designed but not yet built (costs were not available for one of the projects). Based on data collected The Passive House movement is still at an early so far, Passive House costs range widely, from a stage in Minnesota. As documented in the previous custom home at $342 per square foot to a simple section, there are many potential advantages as well single-family home at $100 per square foot. Two as some known challenges that have appeared. Our examples of more conventional high performance research has revealed five certified Passive House houses by Amaris Homes and Christian Builders projects in Minnesota and western Wisconsin at in Minnesota are in the $90-$140 per square foot this time—three single-family houses and two range. Note that Table 1 shows cost per square foot small institutional buildings (a classroom on the information in two ways—TFA (treated floor area) University of Duluth campus and a classroom/ and the ASHRAE method for calculating floor area. dormitory at Concordia Language Village). There The ASHRAE method is the more common way that are also three projects that have been designed and costs per square foot are calculated in the US build- will undoubtedly meet the certification requirements ing industry. Floor areas are measured to outside when built. One of these is a prototype Passive walls and include all partitions and stairs. The TFA House and the other two are designed for clients method is used in the Passive House software and in northern Minnesota. In addition, there are a does not include wall thicknesses and unconditioned number of high performance houses that are close spaces. It should be noted that there can be quite
20 College of Design Passive House and High-Performance Housing
significant differences between the two figures. a code building in Minnesota. In addition, four of Compounding this issue is that professional apprais- the houses include photovoltaic (PV) solar systems ers cannot legally count any below grade space, in the cost. While the PV systems are part of the regardless of grade, finish, or space conditioning. overall strategy to attain net zero energy in these houses, they are a costly way to reach that goal and The cost differences shown in Table 1 cannot be tend to obscure the cost of the house itself. attributed solely to energy-efficiency improvements because of the difference in finish materials and The case studies typically do not clearly identify other design features. The Passive House profes- the added costs for Passive House construction. sionals interviewed for this report estimate a 3% In the process of developing the Synergy Passive to 20% cost increase to build a Passive House over House prototype home, TE Studios performed some
Table 1: Construction Costs of Case Studies (ft2) (ft2) $/ft2 $/ft2 Project Location HDD TFA ASHRAE Cost TFA ASHRAE Certified Isabella Isabella, MN 9818 2134 53842 $1,841,328.00 $862.85 $342.002 Passive House Konkol Hudson, WI 7876 1973 2757 N/A N/A N/A (all include PV) Newenhouse Viroqua, WI 7795 833 1233 $254,000.00 $304.92 $206.00
Skyline Duluth, MN 9900 2660 2950 $775,000.00 $291.35 $262.71 Non-certified Synergy* Minneapolis, MN 7876 1692 2300 $321,805.00 $190.19 $139.92 Passive House Synergy (no PV)* Minneapolis, MN 7876 1692 2300 $299,000.00 $176.89 $130.00 Holm* Biwabik, MN 9818 1531 2200 $230,000.00 $150.23 $104.55 Erickson* Ely, MN 9818 1060 1500 $150,000.00 $141.51 $100.00
High-performance Stemwell House Plymouth, MN 7882 43061 4306 $388,721.04 $90.271 $90.27 Walker House Rogers, MN 7981 33561 3795 $367,122.00 $109.39 $96.74 *Not yet constructed or not yet completed (estimates only). 1Calculated conditioned floor area, not true TFA. 2Figure includes ALL enclosed space, including unconditioned areas.
Table 2: Passive House Initial Construction Cost Comparison MN Code Passive House Cost Increase Building Envelope $54,291.00 $66,315.00 22% Fenestration $18,800.00 $51,632.00 175% Mechanicals $17,700.00 $23,300.00 32% Other $108,058.00 $108,058.00 0% Site $50,000.00 $50,000.00 0% Total $248,849.00 $299,305.00 20% PV for Zero Energy $125,000.00 $22,500.00 -82% Total Zero Energy $373,849.00 $321,805.00 -14% Calculations performed by TE Studios based on a two-story, 1,667 single-family home.
College of Design 21 Passive House and High-Performance Housing
Table 3: Energy-Efficient Home Initial Construction Cost Comparison Code Code Upgraded Upgraded Cost R-value Cost R-value Cost Difference Above Grade Sheathing/framing $2,592.89 $3,636.60 $1,043.71 Wall insulation R-19 $938.40 R-26.5 $5,278.50 $4,340.10 Ceiling insulation R-38 $983.84 R-60 $2,649.66 $1,665.82 Below Grade Wall insulation R-10 $1,159.20 R-24 $4,567.20 $3,408.00 Underslab insulation R-0 $- R-10 $1,173.90 $1,173.90 HVAC system upgrades Upgrade to Variable Speed Furnace $700.00 $700.00 RenewAire ERV System $1,500.00 $1,500.00 Upgrade to 14 SEER A/C $500.00 $500.00 Upgrade from 14 SEER to 15 SEER Heat Pump $800.00 $800.00 Zone Controls $2,100.00 $2,100.00
Totals $5,674.33 $22,905.86 $17,231.53 Cost per square foot $2.54 $10.24 $7.71 Based on 2,236ft2 home. Source: Amaris Custom Homes
Table 4: Predicted Energy Performance of Case Studies
Total Annual Heating (Btu/ft2)/ Annual Total Energy TFA Heating (kBtu/ft2 yr/(HDD/ Energy per ft2/yr. Location HDD (ft2) (Btu) TFA/yr) yr) (Btu-site) (Btu) Isabella Isabella, MN 9818 2134 9600000 4.50 0.45820 0 0.00 Isabella no PV Isabella, MN 9818 2134 9600001 4.50 0.45820 13000000 6.09 Certified PH Konkol Hudson, WI 7876 1973 6208168 3.15 0.39951 -9153037 -4.64 Konkol no PV Hudson, WI 7876 1973 6208169 3.15 0.39951 13867353 7.03 Newenhouse Viroqua, WI 7795 833 3915100 4.70 0.60295 0 0.00 Newenhouse no PV Viroqua, WI 7795 833 3915101 4.70 0.60295 9245000 11.10
Skyline Duluth, MN 9900 2660 19410000 7.30 0.73707 39900000 15.00 Synergy* Minneapolis, MN 7876 1692 7464135 4.41 0.56011 0 0.00 Non-certified PH Synergy no PV* Minneapolis, MN 7876 1692 7464136 4.41 0.56011 18923000 11.18 Holm* Biwabik, MN 9818 1531 1837200 1.20 0.12222 15310000 10.00 Erickson* Ely, MN 9818 1060 1166000 1.10 0.11204 10494000 9.90
High-performance Stemwell House Plymouth, MN 7882 4306 38100000 8.85 1.12257 103000000 23.92 Walker House Rogers, MN 7981 3356 62900000 18.74 2.34840 129600000 38.62 *Not yet constructed or not yet completed
22 College of Design Passive House and High-Performance Housing detailed cost analyses and arrived at a number of It is possible to achieve very good energy perfor- relevant conclusions. Their calculations are based mance with more conventional construction using on two versions of a two-story 1,667 square-foot advanced practices such as greater amounts of single-family home (Table 2). The first model is insulation, air sealing, and more efficient mechanical built to meet the Minnesota code, and the second systems. Table 3 shows the cost increases in the $10 model meets Passive House performance criteria. per square foot range for these items provided by They estimate a 20% increase in initial construc- one contractor based on a 2,236 ft2 home. tion costs to build a Passive House instead of a Minnesota code minimum house. If the expenses Energy Performance are included for a net-zero photovoltaic system, the As shown in Table 4, predicted total energy use for Minnesota Code home requires such a large array to all Passive House projects is quite low—below 20 meet its energy needs that it winds up costing more kBtu/sf-yr. In the four cases using PV solar systems, than the Passive House with PV. net energy use is zero (or in one case a negative number because it produces more than it uses). The
45
Total energy use per square foot per year 40
35
30
25
20
kBtu/ft2/yr 15
10
5 Net zero energy Net positive energy Net zero energy Net zero energy 0
-5
-10 Konkol Skyline Holm* Isabella Synergy* Erickson* Newenhouse Konkol no PV Konkol Walker House Walker Isabella no PV Synergy no PV* Synergy Stemwell House Stemwell Newenhouse no PV
College of Design 23 Passive House and High-Performance Housing
two more conventional high performance houses use best practices such as a well-insulated, airtight 24 and 30 kBtu/sf-yr by comparison, and achieved envelope and highly efficient mechanical systems. Home Energy Rating Systems (HERS)** ratings of 40 and 57, respectively (where 0 is no energy use Life Cycle Cost Comparison and 100 is a typical code building meeting the 2006 Considering the limited number of Passive Houses IECC). A HERS rating of 85 or below qualifies for built so far in Minnesota and the wide range of the US EPA Energy Star program and a rating below construction costs, it is too early to draw definitive 60 is considered very good. conclusions about cost versus performance. Usually, there is no clear side-by-side calculation available of In one interview, Ray Pruban of Amaris Custom the costs and benefits of a Passive House compared Homes also noted very good performance at little to a more conventional alternative. However, there to no additional construction cost in two other is one example that illustrates some of the tradeoffs. projects. One was a LEED for Homes project in In their case study of the Synergy prototype Pas- Hugo, Minnesota that achieved a HERS rating of sive House, TE Studios provided a side-by-side 47 that was built for $229,000 excluding lot (1,624 comparison of cost and energy for three scenarios ft2 of conditioned space and 800 ft2 unconditioned). shown in Table 5. These are 1) A base case house Another was a 3400 ft2 LEED for Homes project meeting the Minnesota code, 2) The Synergy Pas- in Northfield, Minnesota that was built for ap- sive House prototype, and 3) The Synergy Passive proximately $400,000 ($117/ft2) excluding lot and House with enough photovoltaics (PV) to meet the achieved a HERS rating of 20. Amaris Homes apply net zero energy goal. Construction estimates range from $248,849 for the base case to $299,305 for ** The software used to calculate HERS ratings does not adequately calculate certain aspects of Passive House design. This is a known the comparable Passive House. The addition of PV issue and is currently being resolved between the Passive House Institute of the US, and the Residential Energy Services Network. to meet net zero energy costs $22,500. Costs per
Table 5: Passive House Cost and Energy Comparison Base Synergy PH Synergy PH with PV kWh/yr (site) 30880 5546 0 kWh/sf/yr 18.5 3.3 0.0 annual energy cost $1,456 $554 $0.00 annual maintenance cost $2,488 $1,244 $1,244 savings over base $2,146 $2,700
cost $248,849 $299,305 $321,805 cost/sf $149 $180 $193 cost above base $50,456 $72,956 Energy costs are extrapolated from Synergy report as follows: $488.84 per year natural gas (44,440 kBtu per year @ $1.10/therm) $432.00 per year electricity (4,320 kWh per year @ $0.10/kWh) Source: TE Studio
24 College of Design Passive House and High-Performance Housing
square foot range from $149 to $193 across the three cost savings over the lifetime of both Passive scenarios. Projected annual energy and maintenance Houses compared to the conventional code house costs appear in Table 5, and show an annual cost going into the future once the breakeven point has savings over the base case for the two Passive House been crossed. scenarios. Understanding Life Cycle Costs In their case study report, TE Studio performed a There are many ways to analyze the costs and life cycle cost analysis for the three scenarios shown benefits of a more energy efficient house. Each in Table 6. Assuming a 6.5% energy inflation rate, method has its advantages and disadvantages and the Synergy Passive House costs less to own and they are based on several assumptions that may operate after approximately 19 years. The Synergy change in the future. The conclusions drawn from Net Zero Passive House costs less to operate after any such life cycle cost analysis do not necessarily 21 years. As the graph shows, there are significant take into account all of the relevant factors in the
TE Studio Life Cycle Cost Comparison Chart $900,000
$800,000
$700,000
$600,000
$500,000 Base
$400,000 Synergy
$300,000 Synergy Net Zero
$200,000
$100,000
$- Year 1 Year 10 Year 20 Year 30 Year 40 Year 50
Table 6: TE Studio Life Cycle Cost Comparison Base Synergy Synergy Net Zero Year 1 $252,294 $300,854 $330,299 Year 10 $288,395 $316,731 $339,247 Year 20 $345,187 $340,722 $349,190 Year 30 $434,351 $377,036 $359,132 Year 40 $584,282 $436,480 $369,075 Year 50 $848,281 $539,345 $379,017
Includes estimated maintenance expenses and 6.5% annual energy inflation rate. Source: TE Studio
College of Design 25 Passive House and High-Performance Housing
decision making process. Tables 7 and 8 show Simple Payback 1 (with no energy inflation rate). the results of several ways of looking at life cycle The most basic payback calculation is to divide the costs based on the basic data from the TE Studio investment (added construction cost) by the annual comparison presented in the previous section. The cost savings to obtain the number of years it takes analysis in Table 7 is based on energy cost savings for the cumulative cash flow to reach zero. In Table only while the analysis in Table 8 includes savings 7, this number is 56 years for the Passive House and in both energy and maintenance costs for the Passive 50 years for the Net Zero Passive House based on Houses. energy cost savings alone. In Table 8, the payback period is 25 years for both the Passive House and
Table 7: Life Cycle Cost Comparison (Energy costs only) Base Synergy Synergy Net Zero Initial construction cost1 $248,849.00 $299,305.00 $321,805.00 Construction cost increase over base case house $50,456.00 $72,956.00 Annual energy cost savings1 $902.10 $1,456.70 Simple payback 1 (assumes no energy cost inflation) 56 years 50 years Simple payback 2 (assumes energy cost inflation2) 25 years 25 years Net present value 1 (2% discount rate)2,3 $1,792.00 $402.00 Net present value 2 (4% discount rate)2,3 $(13,533.87) $(20,575.82) Year 1 net monthly cash flow4 $(180.48) $(248.27) 30 year lifetime cost2,4 (mortgage + energy costs) $560,236.83 $575,801.74 $586,993.92 Notes: 1TE Studio estimate. 2Energy inflation rate of 6.23% natural gas and 3.75% electricity. Figures based on annual cost averages 1970-2009 from www.eia.gov. 330 year NPV. 4Based on 30 year mortgage of initial construction cost at 4.5% interest rate with no down payment.
Table 8: Life Cycle Cost Comparison (Energy and Maintenance costs) Base Synergy Synergy Net Zero Initial construction cost1 $248,849.00 $299,305.00 $321,805.00 Construction cost increase over base case house $50,456.00 $72,956.00 Annual energy cost and reduced maintenance savings1 $2,146.35 $2,700.95 Simple payback 1 (assumes no energy cost inflation) 24 years 27 years Simple payback 2 (assumes energy cost inflation2) 18 years 15 years Net present value 1 (2% discount rate)2,3 $29,658.99 $28,268.94 Net present value 2 (4% discount rate)2,3 $7,981.66 $939.71 Year 1 net monthly cash flow4 $(76.79) $(144.58) 30 year lifetime cost2,4 (mortgage + energy + maint. costs) $634,891.53 $613,129.09 $624,321.27 Notes: 1TE Studio estimate. 2Energy inflation rate of 6.23% natural gas and 3.75% electricity. Figures based on annual cost averages 1970-2009 from www.eia.gov. 330 year NPV. 4Based on 30 year mortgage of initial construction cost at 4.5% interest rate with no down payment.
26 College of Design Passive House and High-Performance Housing the Net Zero Passive House when energy and result of an NPV calculation is a positive number maintenance cost savings are included. over the time period specified, it is considered a good investment, if it is a negative number it is not Simple Payback 2 (with energy inflation rate) a good investment. Net Present Value 1 in Tables 7 The Simple Payback 1 approach described above and 8 shows the results of NPV calculations with does not account for the fact that energy costs are a 2% discount rate. Net Present Value 2 shows the likely to increase over time. Simple Payback 2 in results of NPV calculations with a 4% discount rate. Tables 7 and 8 shows the number of years it takes The discount rate represents the cost of borrowing for the cumulative cash flow to reach zero with an money or earning interest on money and must be energy inflation rate of 6.23% for natural gas and established by the individual. Net Present Value 3.75% for electricity (based on 30 year averages in 1 (2% discount rate) is a positive number over 30 Minnesota). In Table 7, this number is 24 years for years in Table 7 for both the Passive House and the Passive House and 27 years for the Net Zero Net Zero Passive House meaning they are good Passive House based on energy cost savings alone. investments over the time period of the analysis. In Table 8, the payback periods are 18 and 15 years Net Present Value 2 is a negative number in Table respectively when energy and maintenance cost 7 (energy savings only) for both Passive Houses savings are included. The inflation rate is applied meaning that it is not a good investment when the to the energy cost only, not maintenance. The discount rate is 4%. However in Table 8 where both Simple Payback 2 method including energy and energy and maintenance costs are included, both maintenance cost savings was used by TE Studio in Passive Houses are a good investment with a posi- their life cycle analysis with a 6.5% overall energy tive NPV at a 4% discount rate. inflation rate. Net Monthly Cash Flow Net Present Value Net Monthly Cash Flow analysis is another way to Simple payback analysis has its shortcomings. It evaluate an investment in energy efficiency. The does not account for cash flow that occurs after monthly mortgage payment is calculated for the payback has been achieved and does not measure additional money spent for the energy efficiency the long-term value of an investment. It also ignores improvement. This is compared to the monthly the time value of money—the principle that money energy savings. Any investment with a positive net received in the future is not as valuable as money re- monthly cash flow is attractive to the homeowner. ceived today. Net Present Value (NPV) is an analysis Net monthly cash flow is negative for both Passive tool that accounts for the time value of money by House scenarios in Table 7 when only the energy discounting cash flows that occur in the future. If the savings are considered. In Table 8 where energy
College of Design 27 Passive House and High-Performance Housing
and maintenance savings are considered, the net fective way to meet these goals. The second is to ask monthly cash flow is still negative in both cases but what is a cost-effective level of investment in energy the amount is smaller. In both cases, the mortgage efficiency measured by payback, net present value, interest rate is 4.5%. and other conventional economic analysis tools. Simple payback periods based on no energy cost 30-Year Lifetime Cost inflation over 30 years might be considered too long. A final method of comparing alternative scenarios is However, with the inclusion of energy cost inflation 30-year lifetime cost. This represents the total of the estimates and maintenance cost savings, the payback initial construction cost, the energy costs, and the period can be significantly less (as low as 15 years). cost of the mortgage payment on borrowed money The Net Present Value method of cost analysis over 30 years. In this calculation, the present value produces a range of results as well. The investment of money spent or saved in the future is not taken is positive (worth investing) when the discount into account. In Table 7 where maintenance costs rate is 2% but it is negative (not worth investing) are not included, the 30-year Lifetime Cost for the when the discount rate is 4%. Other methods show Passive House is $575, 802 versus $560, 237 for the negative monthly cash flow for energy savings alone base case (a 3% increase). The lifetime cost for the as well as when both energy and maintenance cost Net Zero Passive House is $586,994 (a 5% increase savings are included. Similarly, the 30-year lifetime over the base). In Table 8 where energy plus mainte- cost is slightly higher for the Passive House options nance costs are included, the 30-year Lifetime Cost versus the base case when energy costs alone are is $613,129 versus $634,892 for the base case (a 4% considered but are lower when maintenance cost decrease). The lifetime cost for the Net Zero Passive savings are included as well. House is $624,321 (a 2% decrease from the base). There is one key factor in considering long term Life Cycle Cost Summary investments in homes that is not recognized by any The preceding life cycle cost analysis discussion of these life cycle cost analysis methods: That is that is not intended to provide definitive answers about energy efficiency improvements actually increase the economic viability of Passive Houses. Instead, the value of the home. The benefits of the invest- it serves as a means to illustrate the many issues ment are not only monthly energy and maintenance and variables that might be considered in such a savings but also the additional money gained on decision. There are two ways to consider cost- resale of the house due to the improvements. effectiveness. The first is to ask what is the most cost-effective way to reach carbon-neutral or zero- It is important to remember that all of this analysis net-energy targets. Passive House is a very cost-ef- is based on one hypothetical set of data prepared
28 College of Design Passive House and High-Performance Housing by TE Studio to provide information on the af- fordability of the Passive House concept. Changes in key assumptions can significantly change the results and conclusions. For example, the 20% cost premium that TE Studios attributes to Passive House construction is higher than some other designers have noted. As the cost difference is reduced, the life cycle costs are more attractive for the Passive House. Similarly, energy price increases or carbon taxes designed to increase fossil fuel energy prices would make the analysis more favorable for The Nestwerk Passive House multifamily residential project in Dresden, Germany. investing in the Passive House. On the other hand, the maintenance cost savings in the TE Studio Passive House Market Acceptance and Develop- projections have yet to be verified over time. Finally, ment any life cycle cost analysis does not include other There is not enough information at this point on qualitative benefits that are not accounted for such the market for Passive House designs. However, as comfort, health, and security. a rapidly growing movement of Passive House developments implies that developers see a potential Multi-Family Structures market for energy- and environmentally-conscious Because of the relationship of surface area to homebuyers. volume mentioned previously, it is generally easier for larger and multi-family buildings to meet the performance criteria. While the UMORE project is primarily focused on single-family homes, some medium-density multifamily housing is likely to be included, as well. Cost premiums may also decrease with larger buildings as a result of purchasing efficiencies. Many multi-family Passive House projects are found in Europe.
A multifamily residential Passive House project in Germany.
College of Design 29 Passive House and High-Performance Housing
to get a whole series of ‘No’s,’ and keep asking the question, and ask- ing the question, ask ‘why not, why not, why not?’ until you can finally bust through and get someone to say, ‘well maybe if this is done this way,’ then suddenly, ‘yeah, I guess it would work if you did it that way.’ And all you’re looking for is that opening.”
Phase three at the Ecovillage in Ithaca, New York will be another Jackson Meadows sustainable development near Marine on St. Croix, MN test of the Passive House concept at There will be an important regional test of the a development scale in the US. The market for Passive Houses at Jackson Meadows in Third Residential Ecovillage Experience, or TREE, Stillwater, Minnesota where 14 homes will be built is a development designed around the most cutting- to the PH standard as Phase 2 of the development. edge concepts in neighborhood design, including Implementation has been slow because of the gen- rainwater management, district solar energy, and eral downturn in the housing market, but developer Passive House energy performance. The TREE Harold Teasdale remains committed to sustainable project has secured thirty of the forty Joint Venture community design. “Jackson Meadow is all about Partners they need to start the project, and they plan pushing upstream,” says Teasdale. “There’s this to break ground in early spring of 2012. whole system in place. You just have to be willing
Jackson Meadows sustainable development near Marine on St. Croix, MN
30 College of Design Passive House and High-Performance Housing
In Arvada, Colorado, the GEOS development is planning for zero net energy use by combining Passive House energy efficiency measures with solar electric and geothermal systems. Geothermal systems were integrated largely because of the roofspace limita- tions in the density they desired. Three hundred housing units are planned in a mixed-use neighbor- hood with traditional street layout that balances solar access with New Urbanist densities. Developer Norbert Klebl estimates that home- The layout of multiple Passive House buildings at the Third Residential EcoVillage Experience (TREE) in Ithaca, NY. owners will be able to purchase the homes at no additional cost, because the increase in mortgage payments will be more than offset by the energy cost savings.*** There are currently 12 interested homeowners, but the project remains idle until more funding is secured.
Layout to Optimize Solar Gain Passive House takes much of its inspiration from the solar and energy efficient housing movement of 1970’s America. One of the most basic concepts is how to design the building and the neighborhood to maximize use of solar energy. The solar-optimized layout may be different than that of a typical development. The first Layout to optimize solar access along a North-South access in Denmark. principle is that buildings should not shade each other in the winter months, when the need for solar gain is highest. Proper orientation and spacing of buildings, along with careful tree selection and placement, will ensure adequate solar gain to meet the energy perfor- *** Boulder Green Building Journal, Spring 2007.
College of Design 31 Passive House and High-Performance Housing
An example of spacing and layout for optimal solar gain on a cluster of one-story houses. The shadows represent the sun’s angle at 2pm on Dec. 21st in Rosemount, MN.
An example of spacing and layout for optimal solar gain on a cluster of two-story houses. The shadows represent the sun’s angle at 2pm on Dec. 21st in Rosemount, MN.
32 College of Design Passive House and High-Performance Housing mance targets. The figures on the previous page illustrate the spacing required for one- and two-story developments in Minnesota. It is unlikely that this constraint will limit density up to 5-6 units per acre but could result in some unconventional layouts with respect to how units are oriented to streets. One example of a single-family Passive House develop- ment in Denmark has houses spaced apart and angled to face South along a North-South street.
Planners for the GEOS development partnered with the National Renewable Energy Lab to analyze optimal solar layouts for a medium-density develop- ment. The study resulted in a staggered building placement, or “checkerboard” plan, which provides solar access to each building.
Passive House Design and District Energy The “checkerboard” layout to optimize the solar gain of the GEOS development in Arvada, CO. As the need for energy diminishes in individual houses, the economics of district energy systems are affected. During the European tour, comments were The GEOS development is taking a hybrid ap- made that the energy demand for Passive Houses proach, planning to build “mini districts” of 3 to 6 was so low that it was not cost effective to develop homes sharing one water-to-water heat pump with a district energy systems. A study in Montreal, vertical geothermal loop. The homes average around however, concluded that it was more cost effective 1500ft2 and will meet PassiveHouse standards so the to achieve 50-75% of the Passive House standard heat loads including domestic hot water will be less and use a district system to provide the remaining than 10 kBtu per unit. Heat pumps of 3 to 4 tons will energy. This will have to be analyzed on a case- suffice for each district. Energy recovery ventilators by-case basis to determine whether it is more cost will be assisted by earth tubes from REHAU primar- effective to invest in energy efficiency in individual ily for cooling but also for preheating of winter air. houses versus investing in efficient district energy The ERV delivery ducts will distribute the base heat- systems. ing load of about 5 kBtu. The peaks will be covered by small electric baseboard heaters.
College of Design 33 Passive House and High-Performance Housing
Another project under development in Colorado is conventional construction using advanced practices moving farther away from district energy, by reli- such as greater amounts of insulation, air sealing and ance on newly-available smaller ground-source heat more efficient mechanical systems. Two examples of pumps that make unit-based geothermal systems more conventional high performance houses in the more feasible. However, the lower cost of district study are in the $90- $140 per square foot range. systems per unit still makes them financially appeal- ing for the time being. • Considering the limited number of Passive Houses built so far in Minnesota and the wide range of Conclusions construction costs, it is too early to draw defini- • If UMORE is to meet One Planet goals for carbon tive conclusions about cost versus performance. and energy, Passive House design is one viable However, if carbon-neutrality or net-zero-energy approach that is being successfully applied in Min- is the desired goal, Passive House is very likely a nesota and Wisconsin. Several examples of certified cost-effective way to reach those targets. and non-certified but highly efficient houses have been built in the region. Predicted total energy use From a strictly financial perspective, one can use for several Passive House projects is quite low— more conventional economic analysis tools such as below 20 kBtu/sf-yr. Four Passive House designs payback and net present value to determine cost- use PV solar systems to achieve net zero energy (or effective levels of investment in energy efficiency. in one case a negative number because it produces Comparing the Passive House to a Minnesota house more than it uses). The two more conventional high built to meet code, simple payback periods based performance houses in the study use 24 and 39 kBtu/ on no energy cost inflation over 30 years might be sf-yr by comparison. considered too long (over 50 years). However, with the inclusion of energy cost inflation estimates and • Cost premiums for Passive House construction maintenance cost savings, the payback period can are estimated in the 3-20% range. Based on data be significantly less (as low as 15 years). The Net collected so far, Passive House costs range widely, Present Value method of life cycle analysis produces from a completed custom home at $342 per square a range of results as well. Looking at energy costs foot to a simple single-family home estimated alone, the investment is positive (worth investing) at $100 per square foot. Because of the range of when the discount rate is 2%, but it is negative (not projects and differences in finish, there is no clear worth investing) when the discount rate is 4%. The side-by-side calculation available of the costs and investment is always positive when both energy and benefits of a Passive House compared to a more maintenance costs are included. Similarly, the 30- conventional alternative. It is also possible to year lifetime cost is slightly higher for the Passive achieve very good energy performance with more House options versus the base case when energy
34 College of Design Passive House and High-Performance Housing costs alone are considered but are lower when tures, followed by net-zero energy structures, and maintenance cost savings are included. then Passive House.
• In addition to decreased energy and maintenance • Because of common walls and more compact costs, the Passive House concept has advantages configuration, it is easier to meet the Passive House including, durability, energy security, passive surviv- standard with multi-family buildings. ability, and occupant health. The Passive House has • Passive House and other low energy designs may growing brand recognition, is easy to use, and holds be used with district energy systems. As the need designers accountable. for energy diminishes in individual houses, the • The Passive House Concept has challenges such as economics of district energy systems are affected. higher initial costs, availability of some high per- This will have to be analyzed on a case-by-case formance components and materials, lack of profes- basis to determine whether it is more cost effective sional engineers capable of developing finely-tuned to invest in energy efficiency in individual houses designs, lack of experienced contractors, potential versus investing in efficient district energy systems. architectural limitations, and concern over possible Decisions regarding district systems should be moisture problems if not built correctly. Many of analyzed against multiple factors, including fuel these challenges are likely to be addressed as the type, long-term fuel availability, and greenhouse gas Passive House movement matures and experience is emissions. gained in the region. • Ideally, neighborhoods with Passive House con- • Passive House is not the only certification pro- struction should be designed to permit solar access gram that will result in significant energy savings for each home. This is unlikely to affect density (although it has an emerging brand recognition as but may require some unconventional layout with a very high standard). Passive House is successful respect to how units are oriented to the street. On because it uses a simple performance standard and the other hand, the Passive House concept can be provides the tools to achieve it. To maintain the carried out with less than ideal solar access. goals of UMORE, a similar type of standard with • UMORE Park could sponsor some type of compe- accountability is desirable. It may be beneficial to tition inviting innovative high performance housing use Passive House in combination with systems such demonstration projects. Passive House would be one as Minnesota GreenStar, LEED, or the Living Build- of these and could be monitored and compared side ing Challenge, for example. Perhaps multiple levels by side with other options. Such a competition could of performance would be appropriate at UMORE with the high end marked by carbon-neutral struc-
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capture the excitement and enthusiasm surrounding Passive House construction.
36 College of Design Passive House and High-Performance Housing
Part 3: Building Survey and Case Studies
The third part of this report comprises a survey of These three groups of houses provide a spectrum Passive House buildings in Minnesota in addition to of construction types related to strategies, costs and a number of other high-performance buildings. The energy performance. buildings fall into three categories: 1. Certified Passive Houses At the end of this section, four more extensive case These houses have received official certification studies are documented to explore performance, cost from the Passive House Institute. Only a few exist and design strategies in greater depth. These are: in the Minnesota-Wisconsin region. • Passive House in the Woods, TE Studio 2. Non-certified Passive House • Synergy House, TE Studio These buildings are designed to meet Passive • Newenhouse, Coulson Architect House standards but either did not pass certi- • Isabella EcoHouse, Compass Rose, Inc. fication or are still in the process of receiving certification. 3. High-performance Houses These houses are not necessarily designed to meet Passive House standards but are examples of energy efficient house design.
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Certified Passive Houses
Waldsee BioHaus Stephan Tanner, Intep LLC The Waldsee BioHaus is a 5,000ft2, two story classroom and dorm complex completed in 2006 outside of Bemidji, Minnesota. It was the first building to be Certified Passive House in the US. It is extensively monitored, and incorporates in- teractive feedback displays that show visitors how the house is performing in real time. It has been exceeding the Passive House performance criteria by 10%-15%. Total project cost was $1,100,000 photo by John Carmody ($220/ft2 gross).
The NewenHouse Prototype I Coulson Architect The NewenHouse Prototype 1 is a two-story, 1250ft2 single-family home completed in 2011 near Viroqua, Wisconsin. It uses a solar hot water system, has PV installed to achieve net-zero, and a rainwater collection system. It is seeking LEED-H Platinum certification and has the highest HERS rating on record for Wisconsin. Total construction cost was approximately $254,000 ($206/ft2 gross).
photo by Sonya Newenhouse
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Certified Passive Houses
Konkol Residence TE Studio The Konkol Residence is a 2,757ft2, three story single-family home completed in 2010 outside of Hudson, Wisconsin. It uses electric resistance in-floor heating with a PV array to generate elec- tricity, and a solar array for hot water heating. It is
designed to operate CO2-neutral. Project costs are unavailable. All electrical use is being monitored.
photo by Chad Holder
Isabella EcoHouse Compass Rose Designs The Isabella EcoHouse is a 5,245ft2 single-family residence completed in 2009 near the Canadian border with Minnesota. Constructed as a live-in research project, the $1,800,000 house incorpo- rates extensively monitored assemblies including electrical storage, rainwater catchment, and liquid and solid seasonal heat storage. It is designed to photo courtesy Compass Rose, Inc. be net-zero and is certified LEED Platinum.
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Non-Certified Passive Houses
Bagley Classroom Salmela Architects The Bagley Classroom building is a 1995ft2, one-story classroom completed in 2010 on the University of Minnesota Duluth campus. It uses a Venmar preheater and a hydronic radiant floor. It is also LEED Platinum certified. Total construction costs were $700,000 ($350/ft2). Monitoring systems track occupant comfort, interior temperature and humidity, PV generation, and all electrical use.
photo by Paul Crosby
Skyline House Wagner/Zaun Architects The Skyline House is a two-story, 2900ft2 single family home, completed in 2008 near Duluth, Minnesota. It uses a hydronic radiant slab and a wood stove for space heating, and a tankless hot water heater paired with evacuated tube solar col- lectors. The construction cost was approximately $775,000 ($220/ft2)
image courtesy Wagner Zaun Architects
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Non-Certified Passive Houses
Esko Farmhouse Wagner/Zaun Architects The Esko Farmhouse is a two-story, 1800ft2 single family home completed in 2009 near Cloquet, Minnesota. It uses a radiant slab, hot water radia- tors, and a wood stove for space heating, and is built “solar-ready.” It is exceptionally air tight, at 0.4 ACH50. Actual costs for all utilities was approximately $100 per month for the year 2009. Construction costs are unavailable.
photo by Gail Olson
Synergy Prototype TE Studio Synergy is a 2300ft2, two-story single-family home that has been developed as a low-energy prototype. As yet unbuilt, it is designed to use an air-to-air heat pump with electric resistance backup heating. Water is heated by a solar ar- ray. Estimated annual heating cost is $218, and estimated total energy cost is $544 per year. Construction costs are estimated to be approxi- 2 image by TE Studio mately $300,000 ($130/ft ).
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Non-Certified Passive Houses
The Holm Retreat Coulson Architect The Holm Retreat is a 1-1/2 story, 2200ft2 single- family home that will be built in Biwabik, Min- nesota. The walls are R-57. Total construction cost is estimated to be $230,000 ($106/ft2).
image by Coulson Architect
The Erickson Home Coulson Architect The Erickson Home is a one-story, 1500ft2 single- family home that will be built in Ely, Minnesota. Total construction cost is estimated to be $150,000 ($100/ft2).
image by Coulson Architect
42 College of Design Passive House and High-Performance Housing
High Performance Houses
The Walker House Christian Builders The Walker House is a two-story, 3795ft2 single- family home completed in 2011 in Rogers, Min- nesota. It uses an HRV and advanced air-sealing
photo by Christian Builders techniques, and it exceeds MN energy code stan- dards. Construction costs were $367,122.
Stemwell House Amaris Custom Homes The Stemwell House is a 4306 ft2 single-family home completed in 2011 in Plymouth, Minnesota. It uses high performance windows, a high-efficiency furnace, and advanced air-sealing techniques. It also uses a high-efficiency boiler for space heating and water heating. Construction cost was $388,721. It has a HERS rating of 40.
image by Amaris Custom Homes
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Case Study I: Konkol Residence (TE Studio)
photos by Chad Holder
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Technical Description: Konkol Residence (Passive House in the Woods)
General Building Info Building description Project name Konkol Residence “Passive House in Building type Single family detached the Woods” Bldg axis or orientation E-W, broad side faces perfectly south Year completed 2010 Footprint 919.03 ft2 PH certified? Yes Gross floor area (ASHRAE) 2,757.09 ft2 Location Town of Hudson, WI Heated living area 1,973.12 ft2 Architect/designer Tim Delhey Eian, TE Studio, Ltd. Heated volume 16,570.66 ft3 Builder Morr Construction External wall area (to ambient) 2,924.23 ft2 Mechanical eng. Tim Delhey Eian, TE Studio, Ltd. & External wall area (to ground) 674.04 ft2 Thomas Brandmeier, Lüfta GmbH Window area S. wall 309.79 ft2 Energy consultants Craig Tarr, Energy Concepts, Inc. Window area N. wall 0.00 ft2 Site and Climate Info Window area E. wall 37.35 ft2 Window area W. wall 193.64 ft2 Climate zone US 6 Total window area 540.78ft2 Elevation 886.75 ft. Wall construction ICF with EIFS Avg. outdoor temps: Wall R-value 68.4 Jan 11.84ºF Roof construction Flat roof on top of I-Joists (hot roof) April 46.4ºF Roof R-value 94.6 July 73.58ºF Basement construction ICF with EIFS October 48.74ºF Basement R-value 68.4 Heating degree days 7876 Slab construction Slab on top of insulation Cooling degree days 699 Slab R-value 58.5 Building Design temps: Window type Aluminum-clad wood tilt & turn Jan -20ºF Window U 0.14 July 95ºF Avg. daily horizontal insolation 3.9 kWh/m2/day Energy Data Avg. daily vertical insolation 3.3 kWh/m2/day Modeled peak load 10,201 Btu (heating) Clearness index 0.5 Modeled annual load 6,208,167 Btu (heating) Avg. annual precipitation 29.41 in. Est. annual energy use 13,867,353 Btu (total) Avg. annual windspeed 10.6 mph Est. heating cost $162.25 (before on-site generation) Utility infrastructure Est. total energy cost $362.43 (before on-site generation) Air tightness 0.25 ACH50 (68 CFM50) Space heating Electric resistance in-floor heating mats HERS index not finalized Electrical generation and storage Photovoltaic, grid-tied Cost Data Thermal generation and storage Solar thermal, tank; Geothermal, heat Total Project cost withheld at client request exchange to ventilation; 23,020,390 Construction cost withheld at client request BTU designed PV generation Cost/sf withheld at client request Ventilation Balanced HRV Estimated additional cost for withheld at client request Water heating Solar thermal with electric on-demand PH construction backup Water consumption Well 30-yr Life Cycle cost withheld at client request Data and performance tracking e-Monitor Other certifications MN GreenStar gold (pending) Additional Notes
Designed to operate CO2 neutral. Designed to generate more energy than it uses.
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Case Study II: Synergy high-performance home (TE Studio)
images by TE Studio
46 College of Design Passive House and High-Performance Housing
Technical Description: Synergy high-performance home
General Building Info Building description Project name Synergy House Building type Single family detached Year completed unbuilt Bldg axis or orientation E-W, broad side faces perfectly south PH certified? certifiable Footprint 1,149 ft2 Location Minneapolis, MN Gross floor area (ASHRAE) 2,299 ft2 Architect/designer Tim Delhey Eian, TE Studio, Ltd. Heated living area 1,693 ft2 Builder unbuilt Heated volume 12,819 ft3 Mechanical eng. Tim Delhey Eian & Philipp Gross, TE External wall area (to ambient) 2,384 ft2 Studio, Ltd. External wall area (to ground) 0 ft2 Energy consultants n/a Window area S. wall 223 ft2 Window area N. wall 27 ft2 Site and Climate Info Window area E. wall 103 ft2 Climate zone US 6 Window area W. wall 40 ft2 Elevation ~800 ft. Total window area 392 ft2 Avg. outdoor temps: wall construction Double-stud w/ cellulose Jan 11.84ºF wall R-value 58.5 April 46.4ºF Roof construction Flat roof on top of I-joists (hot roof) July 73.58ºF Roof R-value 94.6 October 48.74ºF Basement construction n/a (slab-on-grade) Heating degree days 7876 Basement R-value n/a Cooling degree days 699 Slab construction Slab o.t.o. insulation Building Design temps: Slab R-value 44.35 Jan -20ºF Window type Aluminum-clad wood tilt & turn July 95ºF Window U 0.13 Avg. daily horizontal insolation 3.9 kWh/m2/day Avg. daily vertical insolation 3.3 kWh/m2/day Energy Data Clearness index 0.5 Modeled peak load 9,410 Btu (heating) Avg. annual precipitation 29.41 in. Modeled annual load 7,464,136 Btu (heating) Avg. annual windspeed 10.6 mph Est. annual energy use 18,583,547 Btu (total) Est. heating cost $218.70 (before on-site generation) Utility infrastructure Est. total energy cost $544.50 (before on-site generation) Space heating Air to air heat pump (electricity) with Air tightness ≤ 0.6 ACH50 electric resistance backup HERS index n/a Electrical generation and storage Photovoltaic, grid-tied Thermal generation and storage Solar thermal DHW, tank Cost Data Ventilation Balanced HRV Total Project cost Water heating Solar thermal with electric backup Construction cost $250,000 (estimated) Water consumption Municipal Cost/sf $150 (estimated) Data and performance tracking n/a Estimated additional cost for $50,000 (estimated) Other certifications n/a PH construction
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Case Study III: NewenHouse Prototype I (Coulson Architect)
photo by Sonya Newenhouse
photo by Jim Klousia photo by Jim Klousia
48 College of Design Passive House and High-Performance Housing
Technical Description: NewenHouse Prototype I
General Building Info Building description Project name NewenHouse Building type Single family detached (4 occupants) Year completed estimated completion October 2011 Bldg axis or orientation Broad side faces 30º east of due south PH certified? Pending Footprint 1,475 ft2 Location Viroqua, Wisconsin 54665 Gross floor area (ASHRAE) 2,950 ft2 Architect/designer Sonya Newenhouse w/ Dina Heated living area 2,660 ft2 Corigliano & Carly Coulson Heated volume 53,200 ft3 Builder Midwest Earth Builders; Hearth and External wall area (to ambient) 3,311 ft2 Sol Construction External wall area (to ground) 663 ft2 Mechanical eng. Carly Coulson, Michael LeBeau Window area S. wall 333 ft2 Energy consultants Carly Coulson Window area N. wall 30 ft2 Site and Climate Info Window area E. wall 114 ft2 Window area W. wall 60 ft2 Climate zone US 6 Total window area 537 ft2 Elevation 1250 ft wall construction 14” double-stud w/ cellulose Avg. outdoor temps: wall R-value 54 Jan 20ºF Roof construction Parallel chord trusses w/ cellulose April 49ºF Roof R-value 88 July 73ºF Basement construction ICF + 4”XPS October 52ºF Basement R-value 43 Heating degree days 7673 Slab construction 4” concrete over 12”XPS Cooling degree days 485 Slab R-value 60 Building Design temps: Window type Insulated fiberglass frame, tri-pane, Ar Jan 68 F fill, low-E July 68 - 77 F max Window U South facing 0.19, All other 0.17 Avg. daily horizontal insolation 3.9 kWh/m2/day Avg. daily vertical insolation 3.2 kWh/m2/day Energy Data Clearness index Modeled peak load 16,000 Btu (heating) Avg. annual precipitation 33” Modeled annual load 19,400,000 Btu (heating) Avg. annual windspeed 10mph Est. annual energy use 39,900,000 Btu (total) Est. heating cost $300 (includes on-site generation) Utility infrastructure Est. total energy cost $1000 Space heating radiant panel backup Air tightness 0.7 ACH50 Electrical generation and storage grid-connected, roof mounted, HERS index n/a photovoltaic system Thermal generation and storage n/a Cost Data Ventilation 92% HRV Total Project cost n/a Water heating roof mounted solar DHW system Construction cost $775,000.00 with central tank with electric heating Cost/sf $220 (includes garage and exterior element appendages) Water consumption 9500 gallons/yr 4 occupants Estimated additional cost for $72,625.00 (includes solar thermal Data and performance tracking Yes PH construction system) Other certifications EnergyStar Certified and Registered LEED for Homes (applying for Platinum) Additional Notes Utilities expected to be < $50/mo for water and electricity
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Case Study IV: Isabella EcoHome Experiment Station (Compass Rose)
images courtesy of Compass Rose Inc.
50 College of Design Passive House and High-Performance Housing
Technical Description: Isabella EcoHome Experiment Station
General Building Info Building description Project name Isabella EcoHouse Building type Single-family Year completed 2007 Bldg axis or orientation E-W PH certified? Y Footprint n/a Location Isabella, MN Gross floor area (ASHRAE) 5384 Architect/designer Nancy Schultz Heated living area 2134 Builder Brad Holmes, Rod & Sons carpentry Heated volume n/a Mechanical eng. Bill Gausman, System One Control External wall area (to ambient) n/a Energy consultants Mike LeBeau, Conservation Technolo- External wall area (to ground) n/a gies Window area S. wall n/a Window area N. wall n/a Site and Climate Info Window area E. wall n/a Climate zone US 7 Window area W. wall n/a Elevation 1987 Total window area n/a Avg. outdoor temps: wall construction CCSF + densepack cellulose Jan 14ºF wall R-value R-55 April 49ºF Roof construction n/a July 78ºF Roof R-value R-90 October 52ºF Basement construction (Used for heat storage) 16" EPS Heating degree days 9700 Basement R-value n/a Cooling degree days 189 Slab construction n/a Building Design temps: Slab R-value n/a Jan n/a Window type German quad-pane wood frame July n/a Window U S U-0.088; NWE U-0.07 Avg. daily horizontal insolation 3.8 kWh/m2/day Avg. daily vertical insolation 3.2 kWh/m2/day Energy Data Clearness index n/a Modeled peak load 10W/m2 Avg. annual precipitation 21.5 in. Modeled annual load 9.6 mmBtu Avg. annual windspeed 10mph Est. annual energy use 66kWh/m2/yr Est. heating cost $0.00 Utility infrastructure Est. total energy cost $0.00 Space heating hydronic radiant slab Air tightness .5 ACH50 Electrical generation and storage 8.4 kW PV grid-tie w/ Pb-acid backup HERS index 3 Thermal generation and storage Solar heated 500g water tank; taconite heat storage bed; wood stove backup Cost Data Ventilation HRV Total Project cost $1,841,328.00 Water heating Solar w/ 10kW backup boiler Construction cost Water consumption Cost/sf $342 GSF Data and performance tracking pretty much everything Estimated additional cost for n/a Other certifications LEED Platinum PH construction Additional Notes Rainwater collection; green roof; seasonal heat storage;
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Web Resource List Passive House Information Passive House Institute http://www.passiv.de/07_eng/index_e.html Passive House Alliance, US http://phaus.org/home-page Passive House Institute US http://www.passivehouse.us/passiveHouse/PHIUSHome.html Dr. Wolfgang Feist’s Passive House information page http://www.passivhaustagung.de/Passive_House_E/passivehouse.html Passipedia, the Passive House wiki site http://passipedia.passiv.de/passipedia_en/start Passive House Alliance Minnesota http://www.phmn.org/ Minnesota Passive House Practitioners TE Studio http://testudio.com/ Wagner Zaun Architecture http://www.wagnerzaun.com/ Coulson Architect http://www.carlycoulson.com/ Projects and Developers GEOS Development in Arvada, Colorado. http://discovergeos.com/ TREE Ecovillage in Ithaca, New York. http://ecovillageithaca.org/treenew/ NewenHouse developers the Madison Environmental Group, Inc. http://www.madisonenvironmental.com/ Isabella EcoHouse Research Station developers Compass Rose, Inc. http://www.compassrose-inc.com/Home/Welcome.html Jackson Meadow near Stillwater, Minnesota http://www.jacksonmeadow.com/ Amaris Custom Homes http://www.minnesotagreenhomebuilder.com/index.php Christian Builders http://www.christianbulders.com The Walsdee Biohaus at Concordia German Language Village http://www.waldseebiohaus.typepad.com/
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