Super-efficient. Cost effective. Net Zero Energy Homes Rue Evans

Sponsored by the Northwest Energy Efficiency Alliance | Created by the Integrated Design Lab | 20111

Net Zero Energy Homes CASE STUDY 2

PROJECT PROFILE

Sustainability Certifications Passive House | Earth Advantage Platinum | Northwest Energy Star CertifiedOregon High Performance Home | Energy Trust of Oregon Advanced Performance

Rue Evans Passive House

City/State Salem, OregonClimate Zone ASHRAE Climate Zone 4C HDD/CDD 4927/2100Completion Date July 2010Number of Stories 2Number of Bedrooms 3Lot Size .178 AcresGross Square Footage 1,885 SFConditioned Area 1567 SFVolume 21078 cfBuilder/Contractor Bilyeu HomesArchitect Nathan GoodEnergy ConsultantsBlake J. Bilyeu CPHCCost to Build $240,000, $127/SF Occupants 2

Bilyeu Homes, Inc.custom home design and construction

2010 Passive House Conference, Portland, ORCopyright © 2010, Bilyeu Homes, Inc.

Super-efficient. Cost effective.

a.k.a. “16th and Nebraska Passive House”

.17 ACH 50

Tri Pane Serious Windows 0.14 U avg

Raised Heel R-95 Roof

Dbl Stud Wall R 44.1

Suspended Floor over Vented Crawl R-50.8

Solar Thermal with Electric Backup

PV Ready

Fluorescent Tubes and CFL Lighting

95% EfficientERV Ventilation

Ductless Air-AirHeat Pump


GENERAL DESCRIPTIONOVERVIEW

This custom home was designed and built by Bilyeu Homes for Sarah Evans and Stuart Rue. The project is located 40 miles south of Portland, Oregon in the town of Salem. The project resides within a 1920’s neighborhood close to downtown, something the owners desired so they could bike to and from work. The home began its conception in 2009 and was recently finished in July of 2010. The house attempted to attain a healthy, durable, and high performance home that fit the needs of a growing family while satisfying the rigorous Passive House energy standards. The client also prioritized the cost effectiveness of the energy efficiency measures and after a cost benefit analysis between investing in active renewable energy or passive shell and systems design, the decision was made to forego photovoltaic panels. The house is wired and set up to install a photovoltaic array if desired in the future, but the home mainly

focused on reducing the loads and energy consumption of the house to an absolute minimum. According to the energy model, a 3 kW PV array is the estimated amount of generation capacity required to meet net zero for the home. All components of the house were designed to be readily understandable by the trades in terms of constructability and installation, but contain slight modifications to reach maximum performance.

SOUTH ELEVATION EAST ELEVATION

MAIN LEVEL FLOORPLAN



•Three Bedroom, 2.5 bath•1885 Total Square Feet (1567 TFA)

•Certifications: Earth Advantage Platinum, Energy Star, Oregon High Performance Home (Renewable Equivalent Shell Measure pilot house), Energy Trust Advanced Performance House, Quality Approved Passive House Certification

•Custom Home -- Designed and built by Bilyeu Homes for Sarah Evans and Stuart Rue

•CPHC: Blake Bilyeu


DESIGN METHODS PROCESS

Bilyeu Homes is a design build firm whose structure allows them to handle all aspects of the design and construction of their projects. An architect did serve as a consultant, but his input was limited to dealing with the aesthetic issues created by the neighborhood’s older context. The architect mainly worked with the clients to develop strategies for reacting and “fitting in” with the existing older homes in the neighborhood. Architectural expertise also helped mitigate the visual impact of the garage on the overall project. From there, Bilyeu

Homes develop the base plans, elevations, and high performance envelope assembly details. The project team felt that their structure as a design build firm gave them great control over all aspects of the project. They were able to effectively oversee and direct the construction documents, energy modeling, quality control, then implement their own custom design and construction approaches. The structural engineer and HVAC subcontractor were brought on early in the process, but the simple nature of the design made extensive input unnecessary.

ENERGY MODELING

Integral to the Passive House certification process, the program’s requirement to use the Passive House Planning Package (PHPP) energy modeling software for documentation also helped analyze the energy impact of almost every aspect of the project. The software uses monthly energy balances in lieu of dynamic simulation with short time steps, which creates an instantaneous feedback loop ideal for using the energy modeling

tool for design. While the thermal zoning of the house is simplified into one zone in PHPP, very detailed inputs are required for envelope assemblies and window components. These advanced inputs achieve a level of detail greater than most

ENERGY MODEL STATS

Peak Heating(Btu/hr) 2.9

.5-1.2

-0-1.3-1.1-4.8-8.4n/a

-8.4

Peak Cooling(tons)

Annual Heating Demand (kBtu/SF/yr)

Annual CoolingDemand (kBtu/SF/yr)

Lighting/App Energy(kBtu/SF/yr)

Subtotal Energy (kBtu/SF/yr)

PV Production(kBtu/SF/yr)

Net Energy(kBtu/hr-SF)

Hot Water Energy(kBtu/SF/yr) and

MODELED ENERGY END USAGE

Heat Recovery Vent (kBtu/SF/yr)

heating14%

cooling0%

DHW16%

Lighting/Appliances

74%

HRV13%

dishwasher9%

clotheswasher

4%

refrigerator/freezer

27%

cooktop28%

lighting8%

electronics11%

small appliances13%

HRV13%

space heatpump14%

solar thermal/electric backup

16%

heating14%

cooling0%

DHW16%

lighting/appliances

74%

heat recovery13%

57%


PROJECT CERTIFICATIONSThe project team felt that that they were lucky in that the clients were progressive and actively championed the need for a sustainable and energy efficient house. However, Bilyeu Homes introduced the idea of pursuing the Passive House performance standard due to recent Certified Passive House Consultant (CPHC) training undertaken by one of the team members. The Passive House standard doesn’t assign a rating or use a points system like other certification programs. Instead, their standard is based wholly on a building’s pass or fail performance in specific infiltration, annual heating and cooling energy, and total annual energy criteria. A Passive House certified project’s performance cannot exceed more than .6 verified air changes per hour at fifty pascals (ACH50), 4.75 kBtu/sf/yr for heating energy use, 4.75 kBtu/sf/yr for cooling energy use, and a total primary source energy use of 38 kBtu/sf/yr. Passive House defines primary energy use as heating, cooling, DHW, lighting, and appliances energy consumption. The software typically uses a 2.7 multiplication factor to convert site to source energy, which would translate to an approximate total primary site energy use index (EUI) of 15 kBtu/sf/yr. The 4.75 kBtu/sf/yr thresholds only reference the annual heating or cooling energy of the space, while the primary energy requirement takes into account equipment efficiencies and overall consumption. The project’s final site EUI was modeled at 8.44 kBtu/sf/yr, well under the certification requirement. Another key feature of Passive House Certification is that onsite electricity generation cannot be factored into the energy calculation, which forces the project to rely on its energy efficiency without defaulting to using renewable energy to make up for inefficiencies.

Finally, detailed drawings, photographs, product specifications, energy modeling worksheets, and performance testing evidence must be submitted as part of the documentation requirements for Passive House. Passive House certification served as the most important goal for the project team, but multiple other certifications were also achieved including: Earth Advantage Platinum, ENERGY STAR, Oregon High Performance Home, and Energy Trust of Oregon Advanced Performance house.

PASSIVE HOUSE CERTIFICATION REQUIREMENTS

4.75annual heating load kBtus/sf/yr

15total energy kBtus/sf/yr

.6ACH at

50 Pascals

4.75annual cooling

load kBtus/sf/yr

residential energy modeling tools and can take into account specific thermal bridging effects of window components, envelope compositions, and even installation techniques. This allows the software to model the true R-values of the assemblies which adds another level of sensitivity to the details of the envelope. The software can also calculate the effect of concrete slabs, masonry walls, and other high mass constructions on thermal heat balances of the home. Most aspects of the project were iteratively analyzed and designed using the PHPP software to fine tune energy performance to meet the stringent Passive House performance standards. The software calculated the heating energy usage of the project at 4.08 kBtu/sf/yr and the total site EUI of 8.44 kBtu/sf/yr.

In terms of peak load calculation, the software outputs these performance parameters based upon the temperature value of the coldest day rather than the coldest hour traditionally used by standards such as ASHRAE 90.1. This change in methodology allows the software to take into account useful solar and internal gains for the peak load calculation, which can lead to significant peak load reductions and equipment downsizing. The PHPP software calculated a 2.9 Btus/hr/sf peak heating load and a 4 Btus/hr/sf peak cooling load, or roughly a half ton of cooling.

PRO

CES

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The project team chose to incorporate a sealed floor system located over a ventilated crawl space for the floor assembly. The team conducted a literature search to decide upon which system to utilize for their climate and cited the debate “Crawlspaces on Trial” between Joe Lstiburek and Washington State University’s energy program. The resultant modified ventilated crawlspace avoids moisture issues while meeting local expectations and expertise for a wood framed floor rather than a slab. The system’s 1 1/8” plywood subfloor with taped seams serves as the effective air barrier and is placed over 11 7/8” inch I-joists placed 2’-0” on center. All plumbing, electrical, and HVAC penetrations were sealed with EPDM gaskets and 3M ALL Weather flashing tape, which was also used on the seams of the subfloor. The floor/wall air barrier intersection is detailed so that the air tight flashing tape is applied to the plywood panels that run down the exterior rim joist, whose bottom is also taped to

the top of the foundation wall. This creates a continuous air barrier from the subfloor, down the rim joists, to the stem wall, and back up the wall assembly.

The space in between the joists is insulated with dense pack cellulose while 1.5” of type II EPS foam thermally breaks the underside of the joists from the air of the crawl space. The ground floor joists, along with the second story floor, never extend to the exterior rim joist, but are instead terminated at an interior rim joist within the double stud wall. This allows an insulation cavity between the dual rim joist system, which is blocked out with 3” of XPS foam. Thermal bridging is also reduced by the additional two inches of continuous XPS foam that travels down the exterior walls and over the rim joists. For moisture control, the team located a 6 mil poly vapor retarder over the crawlspace floor and also utilized the foam underneath the joists as a vapor retarder. This strategy accommodates the project’s heating climate and favors a drying potential to the exterior.





AIR BARRIER LOCATIONAIR SEALING DETAILS

FLOOR ASSEMBLY ENVELOPE

Vented Crawl Space R 50.8 Joists N/A Perimeter

2” type II EPS

double rim board

R-50 blown indense pack cellulose

1.5” type II EPS

6 mil poly moisturebarrier

1 1/8” tapedplywood subfloorair barrier

3” rim boardinsulation blocking


WALL ASSEMBLY

The framing portion of the wall is composed of two 2x4 nominal stud walls separated by a three inch offset. Both walls have separate sill plates, which allow the outer wall to bear the load of the exterior roof and the inner wall to handle the second storey loads. Both walls utilize advanced framing with 24” spacing on center, but are offset from one another to optimize assembly layouts. As mentioned before, the second story floor system does not penetrate through to the outer wall, which reduces thermal bridging and avoids the need for additional framing material for trimmers and headers. The assembly layers are as follows, starting with the inside material and working toward the exterior: 5/8” gypsum wall board, 2x4 stud wall, three inches of space between studs (entire 10”cavity contains dense pack cellulose insulation), 2x4 stud wall, ½” plywood sheathing, two inches of type II EPS foam , Tyvek WRB, and Hardi Lap siding.

The insulation strategy for the project combines the idea of dense-packing a double wall cavity with insulation and placing additional continuous rigid foam insulation on the exterior of the wall. This exterior foam, combined with the dense pack insulation that seperates the framing in the two stud walls, help to mitigate thermal bridges in the envelope. Additionally, cellulose was chosen for the main insulating material due to its low impact on the environment and moisture control characteristics.

A TYVEK water resistant Barrier (WRB) behind the rain screen serves as the assembly’s moisture barrier, while the interior of the wall has a class III vapor retarder in the latex paint which maintains interior drying potential . The team felt that by stretegically combining the level of exterior foam insulation, the moisture buffering capacity of cellulose, latex paint, and rain screen, any potential condensation problems were mitigated considering the projects relatively mild climate.

Double Wall Stud-Stud R-44 15” Thick

ROOF ASSEMBLY

21” Raised Heel 24” of Loose Fill Cellulose

4” Insulated Soffit with Dense Pack Cellulose R-95

dbl rim board

dense pack, blown in cellulose

tyvek WRB

The air barrier for the wall system is the same as the floor system: 3M All Weather flashing taped plywood panels. Grace Vycor tape and primer was also used to seal any areas with multiple fastener penetrations, such as the window and door penetrations. However, great attention was paid to how the air barrier connects to the windows, floor, and roof assemblies. The typical wall penetrations were also air sealed with a simple gasket and tape system. Even the R-7 Therma-Tru doors contained upgraded gaskets and a five-point locking mechanism to increase the air tightness of the envelope.

Three blower door tests were conducted throughout the construction of the project. The first test did not generate a valid result due to faulty equipment. A second test was conducted after the doors and windows were installed but before insulation and drywall impeded any remediation efforts. This test resulted in a .26 ACH 50 using the Passive House standard for volume, which is more stringent than traditional calculations. The Passive House volumetric calculation resulted in a value that was 15% lower than traditional calculations. In the final test where interior finishes were applied a .2 ACH 50 was calculated with Passive House methodology and a .17 ACH 50 using traditional volumetric calculations.

taped plywoodsheathing/primary air barrier

Serious tri pane windows 725 series

air space forinsulation

2” type II EPS

2x4” framing

3/4” rain screenHardilap siding

ENVE

LOPE

ACTUAL PERFORMANCE


WINDOW ASSEMBLY

The project utilized fiberglass frame Serious Windows from the product manufacturer’s 725 Series. The fiberglass frames are filled with foam and the two chambers of the triple pane system are filled with krypton gas. The south faceing glazing was selected for its low U-value and high SHGC, which it achieves with a clear glass and HM-99 film. The rest of the window orientations were selected for their extremely low u value and low SHGC. The team mentioned that they would have liked to install the window in the center of the thickened wall assembly according to Passive House recommendations. The standard’s research argues that a center placement of the window achieves the best Psi Value ( installed U-value) and overall heat balance according to THERM 6 simulation analysis. However, the team had to install the windows flush to the exterior siding as a result of budget, local ordinances, the mild climate, and bulk water detailing issues. This does, however, allow the frame to be embedded in the two inches of EPS foam on the exterior of the wall assembly. This window placement, along with the foam filled fiberglass frames, serve to reduce the thermal bridging coefficient of the combined window and wall assembly.

The team also had to take into account more than just the typical NFRC performance values of U-value and SHGC which are typically rated at a specific size of window. The PHPP modeling software requires an increased amount of inputs to accurately model differences in frame to glass ratios due to window sizes. Additionally, the software requires thermal performance values of all the components of the window, including spacer and frame u-values. Even the installation location and details of the window are accounted for in the Psi installation value. The advanced level of specification attempts to more accurately model the net energy balance and thermal bridging effects from the windows in the summer and winter season.

Tri Pane Foam Filled Fiberglass FramesFrames: U-value = .26 PSI spacer = .020 PSI Installation = .030

North, East, West Windows:U-center of glass = .108SHGC = .298

South Windows:U-center of glass = .178SHGC = .563

Pre-manufactured 21” tall raised heel trusses comprise the roof system of the project. These trusses bear only on the outer 2x4 wall system and are covered with 24” of loose fill cellulose. The team created a special detail to handle the roof/wall air barrier intersection. The trusses rest on top of a plywood “shelf” located on top plates of the two exterior walls. This shelf connects horizontal sheets of taped plywood panels fastened to the bottom chords of the trusses with the vertical sheathing of the wall system, which creates an airtight diaphragm through the wall and ceiling. Below the plywood layer underneath the trusses, 2x4 furring strips run perpendicularly to the truss cords and create a wiring chase that does not penetrate the air barrier. Only one plumbing ventilation stack and the solar hot

dbl rim board

#30 felt

1/2” CDX roof sheathing

21” raised heel trusses24” blown in

cellulose

insulationbaffle

water lines penetrated the roof’s air barrier, which were sealed using the same gasket and tape strategy utilized on other sections of the envelope. The wiring chase is also filled with dense pack cellulose which creates an R-95 assembly when combined with the attic’s loose fill insulation.

primary barrier location

ENVELO

PE


Fujitsu Mini-Split Heat pump air to airductless single head SEER = 26, HSPF = 12, COP = 4.11@95deg F- 9,000 Btu/hr @47 deg F- 12,000 Btu/hr @14 deg F- 8,710 Btu/hr

The project used a Fujitsu “Hi-SEER” wall mounted minisplit ductless heat pump for heating and cooling. The single head unit uses a “single-point heating” strategy where there is only one indoor wall cassette unit located in the main living area. The team felt that with such a super insulated, air tight envelope, combined with a 95% efficient ERV, single-point heating could meet both the heating and cooling demand of the house. The team found the smallest and most efficient unit that they could find, but the unit still had approximately

double the capacity of the buildings modeled peak heating load, which was calculated at 4544 Btu/hr at 32 degrees Fahrenheit. Additionally, the modeled cooling load only amounted to 6268 Btu/hr, or roughly half a ton, compared to the 9,000 Btu/hr cooling capacity of the equipment. However, the system does feature variable speed compressors which can ramp up or ramp down system performance depending on capacity requirements. As per local code, small zonal electric resistance heaters were required in all of the bedrooms of the house.

HVAC SYSTEM SYSTEMS

VENTILATION

95% Eff ERV

The ventilation system utilizes a Sterling Ultimateair RecoupAerator 200 DX energy recovery ventilator with 95% efficiency for heating/cooling. In addition to having space conditioning recovery, the ERV unit moderates indoor humidity in the winter and block outdoor humidity in the summer with up to 75% moisture transfer efficiency. The



•Smooth Rigid throughout

•Utilizes Open Web Floor Truss for distribution and ovalized 6” for high-wall distribution on second floor

70-210 CFM @ 34-200 W75% Humidity Eff


The project uses a 40 tube Thermomax Mazdon evacuated solar hot water heating system with a 119 gallon Ruud “Solar Servant” storage tank that contains an electric backup element. The project also incorporates an 84” Power-Pipe Counter-Flow Drain Water Heat Recovery system (DWHR) located in a mechanical room underneath the upstairs bathrooms. The DWHR system recovers waste shower heat in a seven foot long, three inch diameter waste water gravity-film exchange system which preheats incoming cold water to both the mixing valves and the hot water tank itself.

DOMESTIC HOT WATER

Evacuated Tube Solar Hot Water 119 Gallon Tank

Electric Backup 65% Efficient Drain Water Heat Recovery

product also has the capability to provide a range of airflow from 70 CFM to 210 CFM. The returns for the system are located in the two bathrooms, powder-room, kitchen, and laundry-room, while supply inlets are located in all three bedrooms and the main living area. The unit also features central control and boost over-ride timers in the bathrooms to increase air circulation in the home when necessary. To encourage airflow between the different rooms of the house, transfer grills are located above each door. Since the ventilation system is completely decoupled from the heating and cooling system, small ovalized six inch ducts were run through the slim interior wall cavities and open web floor trusses to achieve distribution higher up in the rooms.

ERV VENTILATION LAYOUT

SYSTEMS

70-210 CFM @ 34-200 W


The project’s built cost totaled $300,000 at $159 per square foot with a 20% profit margin. The team calculated the project’s overall cost premium at 6%, an additional $18,000 total or $8.55 dollars extra per square foot over their company’s “base” house. This baseline consists of a 2x6 advanced framed house with one inch of exterior foam, a two head mini split heat pump, a Panasonic Spot ERV, and solar hot water. The project team mentioned the difficulty in disaggregating the component costs of the different parts of the envelope of the house. Consequently, a lot of the assembly premiums were part of the overall framing and insulating cost.

The project received multiple incentives, including the Energy Trust of Oregon’s “Advanced Performance Home” benchmark which amounted to a $4,000 incentive. The project also achieved the Oregon Department of Energy’s “Business Energy Tax Credit – High Performance Home – Renewable Equivalent Shell Measure Path”, an $8,440 tax credit. Certification fees for the project totaled $1,600, $1,000 of which came from the PHPP modeling services taken care of internally within the company. This figure, however, is wrapped up into the overall cost for developing the plans and systems strategies of the project. No cost premiums were incured in this project for photo-voltaics due to the fact that this project chose to defer this cost to a later date when a PV system would be more affordable.

The project uses an energy management system to track the energy use and provide feedback to the owners about their operation of the house. The team installed an “Energy Detective 5000” software system on the clients home computers which can be remotely accessed using Google PowerMeter. The software displays energy usage, peak demand, cost, and many other useful pieces of information. The graph below shows the software’s energy consumption output and cost information displayed on a monthly basis. The max heating bill for the home came out to be $72, the average bill was 57$, and the estimated yearly bill can be extrapolated at around $600. Overall, both the project team and clients have been more than satisfied with the home’s performance.

COST INFORMATION CONCLUSION

Relevant Cost Breakdown$240,000 to build $127-SF

ACTUAL PERFORMANCE

Drain Water Heat Recovery....................Total Window Cost .................................Raised Heel Trusses .............................Lighting System Cost .............................Framing Material and Labor ..................All Exterior Doors and Hardware ...........Total Insulation and Air-Sealing Cost .....Total Solar Hot Water System Pre Incentive ..Heat Pump System ...................................ERV Unit, Ducting, Grilles, and Balancing ....

= $800= $13,300= $2,970= $1,400= $26,000= $2,500= $11,500= $8,240= $3,900= $5,800

$44

$60

$48$47

$56$62

$72

$58 $56

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Actual Energy Consumption (kWh) Cost

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2010-2011 ACTUAL PERFORMANCE


→ The project team learned multiple lessons about the execution of a project to the Passive House standard, along with lessons about the internal and exterior barriers surrounding this type of construction.

→ A design-build project delivery structure gives the builder the most control over the design and construction of the custom nature of high performance projects.

→ The most difficult air barrier challenges included the condensate and overflow lines from the solar domestic hot water tank, mini-split lines, etc. The lines could not rely on condensate from summertime air-conditioning to keep the trap wet throughout the winter. Consequently, a dry Drain-Plus SUPCO DP34 condensate line seal was used on the project, but the team mentioned that they will continue to research alternatives for future projects.

→ Air sealing the house to under a 1 ACH 50 really isn’t that difficult if the trades are educated and on board with the idea. Additionally, multiple blower door tests were key to benchmark and predict final performance.

→ When using the exterior sheathing as the primary air barrier, it was easiest when using platform framing to seal the sheathing seams before the wall is tipped up to avoid extensive ladder work.

→ The team would have relocated the indoor wall cassette for the heat pump to an upstairs location, which would be more beneficial for summertime cooling. The single point heating method could be utilized almost anywhere due to the high performance envelope of the project.

→ Thickened exterior wall profiles limited some door swings to 90 degrees. → It can be hard to get customers to understand the importance and value of hidden details such as air sealing.

It takes a conscious effort to meet and present information to the clients to get them on board with these types of high performance design and construction measures.

→ Non standard techniques and systems confounded building officials and made them skeptical of some techniques. The backup electric resistance wall heaters could have been excluded if the team was willing to fight for their removal.

The project team firmly believes that the future of high performance homes will prioritize energy efficient shell measures over renewable energy systems. Investing in a high performance home with a super insulated and air tight envelope is significantly more cost effective when compared to adding renewable energy systems to reach net zero. Passive House projects can be built to an extremely high level of performance while avoiding the large upfront costs of photovoltaics or other onsite energy generation systems. The Passive House methodology believes that high performance homes reach a cost effective balance at roughly two performance values. The first being a home that is 40% more efficient over a typical code-built project which can be reached with relatively basic energy efficient design measures and without the need for premium HVAC equipment. The second point happens at around 80% efficiency, when a simplification or elimination of HVAC systems can defer large up-front costs. Either way, Passive House supporters argue that these projects are “Net Zero Ready” and this extreme high performance will warrant a smaller PV array to achieve net zero energy performance in the future.

LESSONS LEARNED

THE FUTURE OF PASSIVE HOUSE AND NET ZERO

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• Blake Bilyeu from Bilyeu Homes for providing the information used to create this case study including the drawings, details, photographs, and modeling data for the project

• Skylar Swinford for providing insight and information about Passive House and its certification process, modeling requirements, and design standards

• The owners for providing the utility data on the project from their home energy management system

Case study researched and created by:

Integrated Design Lab Boise306 Sth 30th StreetBoise, ID [email protected]

Authors: Jacob DunnGunnar GladicsKevin Van Den Wymelenberg

Graphics:Jacob DunnAlen Mahic

Funding Provided by:

The Northwest Energy Efficiency Alliance421 SW Sixth Ave, Suite 600Portland Oregon [email protected]://neea.org

Point of Contact:Anne Brink

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SPECIAL THANKS TO

Super-efficient. Cost effective. Net Zero Energy Homes Rue Evans

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Transcript of Super-efficient. Cost effective. Net Zero Energy Homes Rue Evans