A Primer on the Passive House Standard, and a Local Example
By Thomas A. Davidson, P.E. , CPHC (PHIUS) DLB Associates Consulting Engineers with assistance from Troy Hodas, CPHC (PHIUS) Spruce Mountain, Inc.
dlb associates | confidential and proprietary 1 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx LEARNING OBJECTIVES
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Learning Objectives
What is Passive House: A Brief History of the Movement
The Big Picture: Residential Energy Codes, US Building Energy Consumption , CO2 Emissions
Basic Technical Requirements of Passive House (US Version)
Typical Construction Components/ Standards
Example Home – The Wurtsboro NY Net Zero Home ‐ Construction
Example Home – The Wurtsboro NY Net Zero Home ‐ Performance and Lessons Learned
State of NJ Incentives for High Efficiency Residential Construction
Quiz
dlb associates | confidential and proprietary 3 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx WHAT IS PASSIVE HOUSE? A BRIEF HISTORY OF THE MOVEMENT
dlb associates | confidential and proprietary 4 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx Passive House ‐ The First in the World, and in the US
Kranichstein Multi‐family Passive House, Darmstadt, Germany
Smith House, Urbana, Illinois
dlb associates | confidential and proprietary 5 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx Higher Window R‐values allow for Increased Design Diversity
Passive House, West Cork, Ireland
dlb associates | confidential and proprietary 6 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PASSIVE HOUSE – MISSION STATEMENTS
There are actually 2 primary passive house organizations at this point in time: PHI and PHIUS. PHIUS is an ‘offshoot’ of PHI, and they are now separate entities.
The Passive House Institute (PHI) is an independent research institute founded 1996 by Dr Wolfgang Feist. PHI played the R&D role in the development of the Passive House concept. The first pilot project (Kranichstein Passive House, Darmstadt, Germany, 1990) was Europe’s first inhabited multi‐family house to achieve a documented heating energy consumption of below 10 kWh/m²yr (0.93 kwh/sf‐yr)), a consumption level confirmed through years of detailed monitoring.
In the US, PHIUS was founded in 2007 by Katrin Klingenberg, a German Architect who moved to the US.
. The mission statement of PHIUS, a 501(c)(3) non‐profit organization, is:
“To develop and promote North American passive building standards, practices, and certifications for buildings, professionals, and products to create structures that are durable, resilient, healthy, and super energy efficient.” dlb associates | confidential and proprietary 7 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PASSIVE HOUSE – A TRUNCATED HISTORY
1973 ‐ OPEC Oil Embargo
1975 – ASHRAE – First Building Energy Code Released
1976 ‐ “Lo‐Cal” house ‐ Wayne Schick at University of Illinois (included R‐30 Double Wall Construction with thermal break, R‐33 Roof, triple‐pane glazing, Air‐ to‐air HX)
1980’s – a bit of a void, though with research continuing in Europe, US Energy Codes continued to be more efficient
1992 – Energy Crafted Home Program (primarily in Northeast US)
1996 ‐ Dr. Wolfgang Feist founded the Passivhaus Institut – PHI [over 25,000 homes in Germany are currently certified]
2004 ‐ First Certified Passive House in the US – Smith House ‐ Built in Urbana, Il. – designed by German‐born architect Katrin Klingenberg
2007 – PHIUS, a US non‐profit, co‐founded by Katrin Klingenberg and Mike Kernagis
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2014 ‐ USDOE’s Challenge Home evolves into the Zero Energy Ready Home (ZERH) and recognizes need for a low‐energy home to be combined with on‐site renewables to achieve the most cost efficient Net Zero Energy (NZE) threshold
2015 – PHIUS decided that German standard was too rigid, and did independent research (with a US Department of Energy – USDOE ‐ grant) to come up with (climate specific) criteria for certification (PHIUS+ 2015 Passive Building Standard). Buildings designed to this standard perform 60‐85% better than buildings designed to the 2009 International Energy Conservation Code (IECC) .
2017 ‐ There are now about 1,200 housing units nationwide that are PHIUS+ Certified or Pre‐Certified. Multi‐family housing is a large and growing component.
2018 – House Tours are available – search for ‘Passive House Days’ for the dates
dlb associates | confidential and proprietary 9 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx THE BIG PICTURE: RESIDENTIAL ENERGY CODES, US BUILDING ENERGY CONSUMPTION
dlb associates | confidential and proprietary 10 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx US RESIDENTIAL ENERGY CODES – HOW FAR HAVE WE COME?
Energy Use of Residential Housing Stock is still significant
Source for chart below is USDOE October 2008
MEC = Model Energy Code
IECC = International Energy Conservation Code
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CO2 Emissions of US Buildings Exceeds Total Emissions of Japan, France and the UK Combined
Source for chart below is USDOE October 2008
dlb associates | confidential and proprietary 12 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx US BUILDING CO2 EMISSIONS – HOW FAR HAVE WE COME?
Residential Energy is consumed in a variety of ways, but Space Heating is the largest component (30.7%), followed by space cooling (12.3%), water heating (12.2%), and lighting (11%). [2005 Source]
Heating and Cooling together constitute 43% of home energy use
dlb associates | confidential and proprietary 13 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx BASIC TECHNICAL REQUIREMENTS OF PASSIVE HOUSE
dlb associates | confidential and proprietary 14 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PASSIVEHAUS INTERNATIONAL (PHI) – BASIC REQUIREMENTS
The PHI standard requires that the building fulfills the following requirements:
HVAC: The building must be designed to have the annual heating and cooling usage as calculated with the Passivhaus Planning Package be not more than 15 kWh/m2 (4,755 BTU/sq ft; 5.017 MJ/sq ft) per year in heating or cooling energy OR be designed with a peak heat load of 10 W/m2 (930 W/1000 sq ft, or 3173 Btu/ 1000 sq ft.).
Total Source Energy: Total energy (source energy for electricity, etc.) consumption (primary energy for heating, hot water, electricity) must not be more than 60 kWh/m2 (19,020 BTU/ SF, or 20.07 MJ/sq ft) per year.
Envelope Air Leakage: The building must not leak more air than 0.6 times the
house volume per hour (n50 ≤ 0.6 / hour, ACH/ hr) at 50 Pa (0.0073 psi) as tested by a blower door, or alternatively when looked at the surface area of the enclosure, the leakage rate must be less than 0.05 CFM/ SF of envelope surface area.
dlb associates | confidential and proprietary 15 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PHIUS+ 2015 STANDARD – WHY DIFFERENT THAN PHI?
In Germany (and most of Europe) the climatic differences are not as varied as in the US
The PHI standard was applied to the Fairview II House (1667 sf) demonstration project in Urbana, Ill, and resulted in:
R‐60 walls
R‐100 ceiling
R‐70 slab
R‐4.8 windows (including thermal bridges); window area was only 8.5% of total wall area, and 82% had to be South facing
0.6 ACH50 (air changes per hour at 50 Pascal blower door differential pressure)
Some of this constraints are appropriate for an energy efficient home in this climate, but many are not cost efficient. How to Optimize?
dlb associates | confidential and proprietary 16 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PHIUS+ 2015 STANDARD – HOW DOES COST OPTIMIZATION WORK?
Enter the USDOE Optimization Program BEOpt (Building Energy Optimization), free from NREL
Cost and energy efficiency of hundreds of envelope and other products are already entered
User can select which options are to be included in the optimization analysis, and adjust costs if needed
Climatic data is entered
An cost optimization routine looks at hundreds of options, quickly figuring out trends so that optimization can be determined without looking at millions of possible combinations Minimum annual Find minimum, then add cash flow renewables to achieve Net Zero dlb associates | confidential and proprietary 17 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PHIUS+ 2015 Standard – How does Cost Optimization Work?
Example of BEOpt Output showing Optimization Curve with and without PV
dlb associates | confidential and proprietary 18 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PHIUS+ 2015 Standard – Optimization by ASHRAE Climate Zone
One sample page of output ‐ over 1000 localities examined in study
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Atlantic City NJ ASHRAE Zone 4A
Peak Heating Load for Atlantic City (2,000 SF home) is 4.2 * 2000 = 8,400 BTUH
Peak Cooling Load for Atlantic City (2,000 SF home) is 4.5 * 2000 = 9,500 BTUH
A small air‐cooled mini‐split fits the bill for this, but check heating as well as cooling capacity as they are different!
dlb associates | confidential and proprietary 20 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PILLARS OF CONSTRUCTION ‐ TYPICAL COMPONENTS AND STANDARDS
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High R‐Value Thermal Envelope, with NO Thermal Bridges, low leakage
High Performance Windows
Balanced Ventilation Systems
Space Conditioning
Domestic Hot Water
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Thermal Envelope Weather/ Water Barrier (to the outside) Air Barrier (typically toward the outside). Blower door test required as part of PHIUS certification to prove air barrier performance Vapor Barrier requires analysis (smart vapor barriers exist that can open when conditions are favorable to drying construction elements) High R‐value Thermal Breaks (as opposed to thermal bridges), which are achieved by double wall construction, continuous insulation, Structural Insulated Panels (SIPs), etc.)
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Free programs available to look at 2D heat flow through envelope
NO Thermal Bridges!
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High Performance Windows
Triple Glazing is most typical as needed to meet passive house requirements
Justification for triple glazing is often for comfort as much as for energy (less cold radiant energy in the winter)
Quad glazing is now available
R‐values (including frames) now close to R‐10 (>10 with quad windows)
It is possible to reduce weight with polyester films (heat mirrors) rather than glass
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Balanced Ventilation Systems
Fresh air normally brought into bedrooms and living spaces
Exhaust air from bathrooms and kitchen areas
Heat exchangers (HX) almost always used to reduce cost of bringing in outdoor air
HX’s can be static; some have rotating heat and moisture transfer elements
HX’s that only transfer sensible energy are called HRV’s (Heat Recovery Ventilators)
HX’s that also transfer latent energy are called ERV’s (Energy Recovery Ventilators)
Choice of HRV or ERV is Climate Dependent
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Space Conditioning
There are many approaches, but the most cost‐effective seems to be the use of an air‐cooled mini‐split heat pump, as loads for an individual living unit rarely exceed about 12,000 BTU either heating or cooling.
Newer units can operate at temperatures below zero (installations as far North as central New Hampshire) A multi‐family passive Night temperature setback is rare, as house in Maine met Passive the house loses and gains heat so slowly House standards with a that little energy is saved with setback 500‐watt electric baseboard heater (plus a HX for The cost of HVAC in passive houses is so ventilation) low that it helps offset the increased cost of the more energy efficient envelope
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Domestic Hot Water
Most popular design is fairly large tank (50 gallons typical) with integrated heat pump. Heat is rejected to basement (good in summer, not in winter) COP>3
Alternative 1: Electric heat pump models are now available in the US utilizing air source CO2 refrigerant cycle – higher efficiency and heat is rejected outdoors. COP>4
Alternative 2: Solar Thermal. The preheat tank is usually larger (80 – 120 gallons). Final tank can be electric or gas. Collectors are typically sized to provide about 70% of the heating requirement on an annual basis
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On‐Site Energy Generation
NOT part of passive house, but is needed for Net Zero
In NJ, a Certified Passive House qualifies as a Net Zero Energy Ready House (USDOE Designation)
Most passive homes stay on the grid
We know of one multifamily passive house designed for Hoboken, NJ that has co‐generation to allow for connecting to a micro‐grid in case of primary grid failure
dlb associates | confidential and proprietary 29 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PASSIVE HOUSE – Pillars of Construction
Not all Passive House is residential
The term “Passive Building” is becoming more popular. Both PHI and PHIUS can certify commercial buildings
Cornell Tech’s Residential building on Roosevelt Island New Office Building in Frankfurt, Germany
dlb associates | confidential and proprietary 30 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx THE WURTSBORO NY NET ZERO HOME ‐ CONSTRUCTION
dlb associates | confidential and proprietary 31 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PHIUS+ 2015 Standard – Wurtsboro NYS Example
Monticello, NY ASHRAE Zone 6A
Peak Heating Load for Monticello (2,300 SF home) is 6.5 * 2300 = 14,950 BTUH
Peak Cooling Load for Monticello (2,300 SF home) is 1.4 * 2300 = 2300 BTUH (1/4 Ton!)
dlb associates | confidential and proprietary 32 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx Wurtsboro, NY NET ZERO HOUSE – UNDER CONSTRUCTION
Enter Plans Here
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Enter Photo Here
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Enter Plans Here
dlb associates | confidential and proprietary 35 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx Wurtsboro, NY NET ZERO HOUSE – CONSTRUCTION DETAILS
ASHRAE WEATHER ZONE: 6A
Ceiling: R‐67 – Blown in Cellulose
Above Grade Walls: R‐36 ft2 Deg F hr/ Btu or U=0.03 Btu/ ft2 Deg F hr
Foundation Walls: R‐36 or U=0.03
Windows: U=0.13 (R‐7.7) SHGC=0.50 (SHGC = Solar Heat Gain Coefficient)
Slab Floors: R‐20 or U=0.05
Infiltration (Blower Door Test): 324 CFM50 (infiltration at 50 Pascals pressure, equivalent to a 20 mph wind). Normally wind and infiltration is less
Mechanical Ventilation: Balanced Energy Recovery Ventilator (ERV), 79 CFM, 51 watts
Heating and Cooling Units: Air Source Heat Pump (mini‐split) 22.2 kBTUH heating, 9.0 kBTUH cooling 33.0 SEER
Water Heating: Heat Pump, 3.39 Energy Factor, rejection to basement
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ROOF
Truss Roof with 20” of Blown in Cellulose – R67
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WALLS
Insulated blocks (ICFs, think LEGOs), inside and outside of a poured concrete wall. Spacers hold the walls apart
R‐36 total
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SLAB
4” Thick Concrete Slab on top of 4” rigid insulation (R‐20)
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ENERGY RECOVERY VENTILATOR
Air Capacity of 30 – 200 CFM
Apparent Sensible Effectiveness (ASE) of 98%, tested in accordance with CAN/ CSA – C439
Heat Exchanger Type: Rotary matrix polymer moves moisture as well as heat
Filtration: MERV 12
Frost Control: Standard good to 10 Deg F
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HEATING AND COOLING UNIT
Temperature Operating Range: 14F – 115F for Cooling
‐15F to 75F for Heating
Cooling Efficiency: Cooling COP = 5.28 kW/ kW SEER=33
Heating Efficiency: COP= 5.33 kW/ kW HSPF = 14.2 Btu/ W‐hr
Nominal Cooling Capacity: 9,000 Btu/ hr (Min=3,100, Max=12,000 Btu/hr)
Nominal Heating Capacity: 12,000 Btu/ hr (Min=3,100, Max=22,000 Btu/hr)
dlb associates | confidential and proprietary 41 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx THE WURTSBORO NY NET ZERO HOME – PERFORMANCE AND LESSONS LEARNED
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Note that OA Temp <0 Deg F during final hours of trending
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Note that upstairs rooms are about 2 Deg F cooler than downstairs during the winter.
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Resiliency note: The drop in interior temp is less than 1 Deg F per hour during power outage with 30F OA Temp
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The upstairs bath is beginning to develop mold on the ceiling. Ceiling was not required to have moisture-resistant drywall. Microclimate is suspected.
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Note how high the relative humidity levels are in the coldest part of the winter. Note also that the potential for condensation is high without excellent construction.
dlb associates | confidential and proprietary 47 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx PASSIVE HOUSE CONSTRUCTION – COMFORT PER ASHRAE 55
Note how high the relatively high humidity levels make the home feel warmer for the same indoor temperature. In a similar manner the warmer radiant surfaces (walls, windows especially), also make the passive house feel warmer.
dlb associates | confidential and proprietary 48 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx Wurtsboro, NY NET ZERO HOUSE – PERFORMANCE
dlb associates | confidential and proprietary 49 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx Wurtsboro, NY NET ZERO HOUSE – PERFORMANCE
Note how CO2 levels vary nicely between 600‐800 PPM during most of the test period. Spikes happened when guests were present. Levels dropped to near 400 PPM with people away.
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Good Stuff Heating and Cooling Loads can be handled with a nominal 1‐ton mini‐split with one indoor head (run the fan at full speed to get the peak capacity on really cold days) Temperature distribution is excellent between rooms at each floor level Temperature distribution is good between floors, at least in the winter, with a single head (+/‐2 Deg F in main living areas) – might be helped by an additional opening to allow a convection loop to be set up Relative humidity is much higher than a ‘normal’ home in the winter (45% RH on a zero degree F day!) – RH levels in the summer are not known – we’ll instrument and let you know…
CO2 levels are generally in the 600‐800 PPM range with code values of ventilation The house is quite comfortable because there is very little radiant heating and cooling The house is resilient during power failures (less than 1F / hour drop noticed) PV output has exceeded expectations (house was +2500 kWh for the first 8 months) Possible Concerns Code exhaust level of 20 CFM/ bathroom NOT sufficient (Boost switch should have been installed) The ceiling of the bathrooms should have had moisture resistant drywall installed (it was a code requirement for the walls but not the ceiling) Basement is cool in the winter (normally no convection between basement and first floor; lower R‐value for basement floor). Solution was a small electric heater when space is used Possibly high RH levels in the summer: needs further study to find out
dlb associates | confidential and proprietary 51 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx STATE OF NJ – INCENTIVES FOR HIGH EFFICIENCY RESIDENTIAL CONSTRUCTION
dlb associates | confidential and proprietary 52 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx STATE INCENTIVES ($$) FOR HIGH EFFICIENCY RESIDENTIAL CONSTRUCTION NJ CLEAN ENERGY PROGRAM (NJCEP)
HERS is RESNET’s Home Energy Rating System (est. 2006)
RESNET is the Residential Energy Services Network
Largest incentive is over $18,000
dlb associates | confidential and proprietary 53 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx QUIZ
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Question 1: When was the first energy code written, and during what decades were PHI and PHIUS formed?
Question 2: Which passive house organization has a climate‐based performance standard, and why?
Question 3: CO2 emissions of the US Building Stock exceed the entire CO2 emissions of what 3 countries?
Question 4: How much better will a residence designed to PHIUS 2015+ standards perform relative to a residence that meets the minimum standards of the 2009 IECC?
Question 5: Are thermal bridges encouraged in passive house design?
Question 6: What would be the approximate maximum cooling load (to the nearest ton) for a 2,000 square foot passive home located in Teterboro, New Jersey (ASHRAE Zone 5A)?
Questions 7: What is the approximate rebate available with the NJCEP for a Zero Energy Ready Home, with a HERS rating of 30, that does not have any PV installed?
dlb associates | confidential and proprietary 55 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx QUESTIONS?
Tom Davidson [email protected] Troy Hodas [email protected]
dlb associates | confidential and proprietary 56 Printed: 9/13/2018 7:30 AM k:\engineering‐shared\energy audit resources\passive homes\2018 passive house presentation\passive house presentation ‐ 2018 nj ashrae chapter ‐ external distribution.pptx References
1. http://www.coloradogreenbuildingguild.org/
2. https://en.wikipedia.org/wiki/Passive_house
3. http://www.greenbuildingadvisor.com/homes/first‐us‐passive‐house‐shows‐energy‐efficiency‐ can‐be‐affordable
4. https://www.nrel.gov/docs/fy15osti/64278.pdf
5. https://www1.eere.energy.gov/buildings/publications/pdfs/corporate/bt_stateindustry.pdf
6. http://www.njcleanenergy.com/files/file/public_comments/HW%20EE‐RE%20FY2016%205‐14‐ 15.pdf
7. Example House ‐ Plans: Thomas J. Foila, Architect Central Valley, NY
8. Example House ‐ Homeowner: Troy Hodas, Wurtsboro, NY
9. Passive House Institute US (PHIUS): http://www.phius.org/home‐page
10. Passive House Institute (PHI): https://passivehouse.com/index.html
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