DOE Tour of Zero: Net Zero in Seattle by TC Legend Homes
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Northwest builder TC Legend Homes has built a certified U.S. DOE Zero Energy Ready Home that has the distinction of being Seattle’s first true zero energy home, producing as much electricity as it uses in a year.
Rain barrels and proper site grading are among the details that will make this high-performance home durable as well as energy efficient.
The home’s advanced comfort system uses radiant floor heating loops in the exposed concrete slab on the first floor that carry water heated by an ultra-efficient air-to-water heat pump. The exposed concrete is acid stained and sealed for durable flooring that also acts as a thermal mass to absorb and radiate heat from south-facing windows.
Advanced solid-state lighting technology is employed throughout the home to reduce electricity use.
The home’s high-efficiency ENERGY STAR dishwasher, clothes washer, and refrigerator are all the lowest energy use products in their categories.
Natural daylight pours into the home through ultra-efficient triple-pane windows with insulated vinyl frames. The windows have an insulating argon gas fill between the glass panes, and the glass is coated with an invisible low-emissivity coating to minimize winter heat loss and summer heat gain.
High-efficiency ENERGY STAR-labeled ceiling fans supplement the cooling provided by a unique fresh air cooling system that uses fans in the bathrooms, laundry, and kitchen to exhaust stale air while another exhaust fan is turned inward to draw fresh air into the home through a high-capture HEPA filter. The fan can be set to bring in cool early morning air to precool the home in the summer.
This home complies with EPA Indoor airPLUS guidelines, promoting a healthier indoor environment through the use of low-/no-VOC stains and finishes.
One unique water-saving feature of the home was the installation of sinks that recycle hand-washing water to flush toilets.
Low-flow plumbing fixtures save water in the home. In addition, a water-saving landscaping design uses no water for irrigation except for the rain barrel-fed drip irrigation in the vegetable gardens.
Under the radiant floor heating loops, ultra-efficient foundation insulation minimizes heat loss with 4 inches (R-20) of rigid foam insulation under the slab and 2 inches (R-10) along the inside of the foundation walls.
The home is encased in a structural insulated panel (SIP) continuous thermal blanket consisting of 6.5-inch-thick SIP walls and 10.25-inch-thick SIP ceilings.
Extensive air sealing of all seams in the rim joist adds to the comprehensive draft protection provided by the solid SIP panel construction.
The home’s air-to-water heat pump provides ultra-efficient multifunction heating by warming water for the radiant floor heating and preheating domestic hot water.
The 6.4-kW solar electric system installed on the roof meets all of the electric needs of the energy-efficient home over the course of the year.
“The savings are real, the quality is real, and the performance and comfort are beyond what I ever imagined.”
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"With careful planning, we were able to build our DOE Zero Energy Ready Home for $125 / square foot, well below the city’s average of $200 / square foot. Because we have high levels of insulation and produce enough renewable energy on-site to offset all our electrical usage and heating, we actually get money back from the utility. The savings are real, the quality is real, and the performance and comfort are beyond what I ever imagined."
– TC Legend homeowner