DOE Tour of Zero: Cottle Zero Net Energy Home by One Sky Homes
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This 3,000-square-foot home by One Sky Homes is the first U.S. DOE Zero Energy Ready Home certified in the state of California.
The traditional three-coat stucco hides the home’s continuous thermal blanket construction with advanced framed wall technology. The wall construction includes 2-by-6, 24-inch on-center wall framing dense packed with R-23 of cellulose insulation plus a 1-inch thick continuous thermal blanket of rigid foam over the plywood sheathing.
Redwood awnings are more than an architectural feature; this solar window shading helps keep interiors comfortably cool in the summer.
A greywater system captures drainage from showers, vanity sinks, and the clothes washer to provide 80% of the landscape irrigation for the water-saving landscaping.
Hidden behind the exterior stucco finish is dry-by-design wall construction that includes an exterior water barrier along with a ¼-inch plastic mesh ventilated rain screen that creates an air gap behind the stucco for ensured drainage.
Lighting energy use is reduced with a combination of high-efficiency CFLs and ultra-efficient solid-state LED lighting technologies, together with motion sensors, timers, and photocells.
The home is equipped with high-efficiency appliances including an ENERGY STAR-labeled refrigerator and dishwasher.
The home’s ultra-efficient comfort system uses an air-source heat pump with a cooling efficiency of SEER 21 and a heating efficiency HSPF of 10 (far higher than the federal minimum standard of SEER 13 and HSPF 7.7). The energy-saving comfort delivery system features heating and cooling ducts located within the conditioned space instead of an unconditioned attic common in minimum-code homes.
All paint, varnishes, wood board products, and carpet are certified low-/no-VOC as part of a healthful indoor environment that meets the EPA’s Indoor airPLUS program specifications.
The professionally installed balanced fresh air system brings outdoor air to every room via a heat recovery ventilator that employs high-capture filtration technology. The home is also equipped with advanced fresh air cooling technology that circulates and filters naturally cool nighttime air throughout the home to help cool down the house without high air conditioning bills.
An on-demand hot water pump speeds water delivery from the solar thermal water heater to the low-flow plumbing fixtures for significant water and energy savings.
A 6.4-kW solar electric system on the roof produces enough electricity to power the home and an electric car.
The home is built over a crawlspace constructed with an ultra-efficient insulated concrete form (ICF) foundation wall, made with concrete poured inside of foam insulation blocks, that provides a continuous thermal blanket.
Open-web floor joists provide space between the floors of the two-story home and the framing members for an interior comfort delivery system with the heating and cooling ducts inside the home, rather than exposed to the extreme temperatures in an uninsulated attic.
High-efficiency advanced wall framing uses 2-by-6 studs 24 inches apart rather than 16 inches apart, 2-stud rather than 3-stud corners, and other techniques to reduce the amount of lumber and allow more room for insulation.
The foundation water barrier system includes a plastic vapor barrier over a 4-inch base of aggregate rock. A 3-inch-thick thermal blanket of rigid insulation foam is placed on top of the vapor barrier, which will be covered with a crawlspace concrete slab floor for additional energy savings and comfort.
ICF blocks used for the foundation walls consist of two sheets of rigid foam held together by plastic spacers and reinforced with steel bars forming a hollow wall that is filled with concrete for an ultra-efficient foundation system.
"It was comfortable as soon as we walked in."
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"What jumped out initially more than anything was the comfort level of the house. It was comfortable as soon as we walked in."
– Homeowners Bill and Michelle