The Pumpkin Ridge Passive House (3,093 SF), designed by Scott|Edwards Architecture and built by Hammer & Hand, demonstrates the power of super-‐efficient construction to make net zero energy building practical and affordable. The key is to focus first on energy conservation, and Passive House provides the cost-‐effective path.
At Pumpkin Ridge Passive House, the added upfront expense of achieving Passive House is offset by savings on utility bills. The modest increase in the homeowners’ monthly mortgage payment to finance the project as a Passive House is paid for by reduced monthly energy bills, thanks to a 90% reduction in heating demand. To accomplish this, Hammer & Hand ran a thorough parametric analysis on the project, using the power of computer modeling to run literally thousands of simulations of building siting, shape, window placement, wall thickness, and insulation levels to cost-‐optimize the design. Recognizing the project’s success in cost-‐effective building energy transformation, Northwest ENERGY STAR® featured the home as one of six “superefficient demonstration homes” in the Pacific Northwest. Pumpkin Ridge Passive House is Earth Advantage Home Platinum, Department of Energy Challenge Home (ENERGY STAR, Indoor AirPLUS), and Passive House (PHIUS+) certified.
With this level of energy efficiency in place, a relatively modest investment in solar PV (10kw, with a payback of 10 years) brought the project into net zero energy territory. Energy monitoring will determine what side of the NZE line the project falls on after a year of occupant behavior, but at a HERS rating of just 5 the project has achieved “deep green” status, affordably. Furthermore, once the PV system has paid for itself, the homeowners will enjoy positive cash flow from their energy generation for the life of the solar panels.
The team started with a detailed shading and solar access analysis to guide siting and orientation of the house as well as vegetation management decisions. Through this work the team was able to save some big trees that it originally assumed would need to be removed to provide sun. It also gained a detailed understanding of the project’s daylighting potential and solar access, which then shaped the schematic design of the house.
The project’s focus on high thermal performance began at the home’s foundation, with the structural engineer on board from day one to design thermal bridge-‐free details throughout. The foundation is built on high-‐density structural geofoam, for an R-‐30 foundation assembly. The home’s R-‐50 wall includes a 9.5-‐inch Larsen truss and 2x6 stud wall, both filled with cellulose insulation and meticulously detailed for air and water management.
A R-‐ 100 attic insulation system is installed over a perfectly airtight diaphragm air barrier. The home’s windows are triple-‐paned high performance Zola windows, with a U value of just 0.13, which translates to 60% less heat loss than a standard window. Triple-‐paned European solar tubes provide additional daylighting. A system of sliding exterior shades shield bottom floor windows from solar gain as needed.
The home is ventilated with a 90% efficient Passive House-‐certified HRV that supplies fresh-‐air to every bedroom and exhausts air from bathrooms and laundry room. Cooling is provided by a modest ducted minisplit. A very low static pressure high performance duct system distributes heating and cooling throughout the house.
Domestic hot water is produced by a high-‐efficiency heat pump hot water heater. To prevent wasted water at the tap, the home employs an on-‐demand hot water recirculation system, activated by motion sensors in the bathroom and a push button in the kitchen.
To ensure successful installation of the high performance details at Pumpkin Ridge Passive House, the building was rigorously tested throughout the construction process by an independent PHIUS+ rater. Before the team installed insulation, for example, the building shell was commissioned and tested with theatrical fog to ensure it was airtight. Periodic spot checks and blower door fan tests helped measure and verify progress.
Alternative Building Systems: HRV, ducted mini-split, geofoam foundation, Prosoco Wetflash system, Agepan DWD, condensing dryer, cellulose insulation, more.
Appliances: Energy efficient throughout, including Bosch condensing dryer.
Building Envelope: Agepan DWD
Caulks and Sealants: Prosoco Wetflash R-Guard system - FastFlash and Joint & Seam
Central Vac: Yes
Countertops: Chroma manmade stone
Decks: Bison pedestal paver: concrete paver on plastic pedestal
Door/Hardware: Zola high performance exterior doors, WestPac interior doors (solid core flush birch)
Electrical: Circuit-by-circuit energy monitoring by eMonitor.
Exterior Finishes: Cedar with clear cedar coating. Low VOC acrylic on hardiplank and panel.
Flooring: Pre-finished domestic hardwood. Concrete in basement. Marmoleum in entryway. Tile in master bath.
Furniture: furnished by clients
Garage Doors: Liftmaster, controlled by iPhone.
HVAC/Ducts: Mitsubishi ducted minisplit heat pump with sheet metal ducts.
Insulation: Greenfiber all-borate cellulose isulation. Big Sky EPS insulation.
Landscaping: Rainwater harvesting. Replanted with hardy natives.
Lighting: LED throughout.
Paints and Stains: Low VOC StaysClear on all clear interior finishes.
Plumbing Fixtures: Low-flow fixtures. On-demand hot water recirculation system by TACO.
Renewable Energy System: 10kw of Solarworld PV Panels
Roof: 40-year comp.
Specialty Products: I-joists in vertical application for Larsen Truss system.
Structural: Structural Geofoam .
Ventilation: Zehnder 350 Comfoair HRV, fully ducted.
Water Heating: Airtap heat pump hot water heater.
Waste Management: Low-flow fixtures, rainwater harvesting.
Windows/Skylights/Patio Doors: Zola high performance windows and patio doors. Lightway triple pane solar tubes.