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Project Description:
Inspired by issues of global warming, our goal for our new home was to create a comfortable, modern living space that produced more energy than it consumed. We also hoped to produce enough energy to power an electric car to provide the majority of our transportation. And we hoped to do this in a home that would be inviting and that could be built with “green” materials and ambitious, but proven, building techniques.
Of course, we also had aesthetic and other design goals, including aging in place, living exclusively on one floor, if necessary. As the design goals came into focus, we found that design decisions taken for other reasons kept expanding our south-facing roof. So, although great thought and care went into lowering the energy demands of the house, we also saw an opportunity to install a large, grid-tied PV array that would allow us to provide renewable energy back to the grid and reduce carbon emissions beyond what our own house would be saving.
Our goal was not to achieve net-zero by brute force, but to provide as much environmental benefit from our roof as possible. Purchasing an electric car almost as soon as we moved into our house was also a goal.
Our Wheego (the only electric car brand commercially available in our area in 2011) has been our primary source of local transportation since July of 2011. We have driven it over 8000 miles in that time (usually car-pooling to work or errands) and our PV array has provided sufficient power for the house and car with plenty to spare to share with our neighbors and to contribute significant electricity credit to charitable organizations.
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Occupancy Type and Details:
This home is occupied by two people full time. During vacations (one week in December, 17 days in June) the home was occupied by only one person. For five days in August, they left the building unattended.
Days of occupancy: 360
Person Days of occupancy: 696
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Subslab assembly:
4"Continuous Rigid Foam (Type IX EPS)
Foundation wall assembly:
2.5” Continuous Rigid Foam EPS & 5.5” Formaldehyde-free Fiberglass Batts
Above grade wall assembly:
11.5” Dense-pack Cellulose
Flat attic assembly:
16" Dense-pack Cellulose
Cathedral ceiling assembly:
16" Dense-pack Cellulose
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Finances Description:
Building Cost: $809,582, not including site work, design costs, porch or garage.
Includes PV cost AFTER the 30% Federal Tax Credit.
Square Footage of Building, including partly conditioned basement space: 3,644 sf
Cost per SF: $223/sf