DOE Tour of Zero: Charlottesville Infill by Promethean Homes
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This 2,572-square-foot neotraditional home on an infill lot in a 1990s-era development was constructed by Promethean Homes of Charlottesville, Virginia, and certified as a U.S. DOE Zero Energy Ready Home.
Even without solar panels on the roof, this high-performance home achieves a Home Energy Rating System (HERS) score of 33, far below the HERS 100 score typical of new homes. The home is expected to save its owners about $1,600 a year in utility bill savings.
Although the home architecture complements neighboring properties, it takes performance to a whole new level including ultra-low energy bills, engineered comfort, a healthful environment, advanced technology, and enhanced durability.
Carefully designed solar window shading helps keep heat out during hot summer weather.
Low-/no-VOC certified paints and finishes are used for a healthier indoor environment.
This home uses an ultra-efficient heat pump system (21 SEER, 12.2 HSPF). Short duct runs between floors and above a dropped ceiling create an interior comfort delivery system that keeps ducts away from extreme attic temperatures.
Advanced solid-state lighting technology with LED lamps is used in 85% of the fixtures, while fluorescent lighting is used in most of the remaining fixtures.
High-efficiency wall framing uses 2-by-6 studs spaced 24 inches apart instead of the standard 16 inches on-center, single instead of double top plates, and other details that reduce the use of lumber while increasing space for insulation in the walls.
Comprehensive draft protection includes rubber gaskets at all pipe and wiring penetrations, sealing every seam in the plywood sheathing with a liquid sealant, and taping seams between the slab and foundation walls. The home is so airtight it exceeds the most rigorous industry standards for air sealing set by Passive House.
The 5.5 inches of cellulose inside the walls is combined with a continuous exterior thermal blanket made with a 2-inch thick layer of bug-resistant, fire-resistant, rigid mineral wool insulation on the outside.
Dry-by-design wall construction includes house wrap and moisture-resistant rigid mineral wool insulation over plywood sheathing that is topped with 1-by-4 vertical furring strips to create a ventilation gap that ensures complete draining behind the fiber-cement siding.
The home’s ultra-efficient windows have three layers of glass with special coatings plus insulated fiberglass frames to minimize heat transfer.
The home’s ultra-efficient foundation insulation system includes 2 inches of rigid foam installed along the inside of the foundation walls plus 4 inches of foam under the floor slab to provide a continuous thermal boundary. This foam layer, together with a vapor barrier sheet installed over a 4-inch base of aggregate rock, comprise a comprehensive foundation water barrier system.
"Our electric bills have been remarkably low -- and that's been a welcome change."
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"We're appreciating the comfortable, steady temperatures in the house, day and night. No drafts, no sudden changes. The prompt hot water delivery is quite a treat. We rarely hear outside noises. Our air exchanger appears to trap any fine dust and we don't have to breathe it – so we've been quite healthy since we moved in at the beginning of last July. Our electric bills have been remarkably low – and that's been a welcome change."
– Homeowners Bob and Jean