2012 Challenge Participant:
Applicants: Jamie Wolf - Builder, Paul and Diane Honig - Homeowner
Project Address: Harwinton, CT
Bdrms./Sq. Footage: 4 BD - 3,561 sq ft
Builder Website: www.homesthatfit.com
Paul & Diane Honig's home in Harwinton is designed and built by Wolfworks, Inc. according to the International Passive House standard. Passive House design and construction assure the remarkably low energy demand that is ideally aligned with the goals of the Zero Energy Challenge: to first maximize energy efficiency and subsequently focus on on-site generation.
Passive House Design
Passive House is a rigorous and uncompromising building energy design and performance standard developed and proven in Germany, being embraced internationally and now gaining ground and admiration in the US for its impressive performance. There is no dictate about style. To be certified as a Passive House the home must achieve three strict performance criteria:
- Heating Energy Demand less than 4.75 Kbtu/sf/yr
- Air leakage less than 0.6 ACH50
- Primary Energy Demand for all building energy needs less than 38 Kbtu/sf/yr
Passive House assures that a building takes the greatest advantage of available “gains” while minimizing energy “losses.” The resulting “energy balance” provides a building with exceptional comfort and health, simplified operation and dramatically lower operating costs.
Orientation and Envelope:
The house is a simple two story 28' x 44' rectangle, oriented 14 degrees from true south to relate to desired site features while allowing the south facing windows to capture solar energy. Triple glazed Tilt-Turn windows from Germany provide the capacity to assure that the net performance of all the windows is gaining more energy than they are losing on an annual basis. In a sense, the windows are providing some of the energy we have traditionally depended on mechanical systems to provide.
Insulation and Air Sealing:
- “Sandwich Wall:” a double stud 12" wall with dense pack cellulose in the two 2x4, 24" on center exterior walls and foam panels in the 5" center
- Ceiling created by the truss roof is sheathed and taped with no penetrations to maintain a continuous air barrier
- Extreme detail to reducing thermal bridging (calculations using THERM software)
- Rigorous attention to the sealing of all potential sources of air leakage
- Intermediate infiltration testing to remediate any leakage discovered during testing
Heating, Cooling, and Hot Water:
With an extremely low peak heat load of 10.6 Kbtu/hr this house could be served by approximately two hair dryers. A Mitsubishi ducted mini-split air source heat pump will provide both heating and cooling for the small load this home requires.
The domestic hot water is a system requested by the homeowner using a large storage tank, a coil of PEX tubing for heat exchange and electric tankless backup. Another strategy planned is a drainwater heat recovery system which uses the hot water coming down the drain from showers to pre heat the water to serve the shower.
This extremely tight home will benefit from the control of constant fresh air provided by a highly efficient Zehnder heat recovery ventilation system. In standard construction, natural ventilation is uncontrolled and the source of considerable heat loss. This balanced system recovers most of the heat from the steady and balanced flow of air it is designed to regulate, allowing the home to constantly breathe.
House lighting will consist of LEDs and CFLs in nearly all fixtures. The most energy efficient appliances have been selected, including an induction range.
The 10kW photovoltaic array is designed to provide all the energy necessary, on an annual basis, to power the home and all its functions, as well as the capacity to charge an electric vehicle.