DOE Tour of Zero: Lakeside Cottage by BPC Green Builders
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BPC Green earned a U.S. DOE Zero Energy Ready Home certification on this ultra-efficient lakeside cabin in west Connecticut.
BPC Green’s two-story cottage features a south-facing roof that provides maximum space to install solar panels in the future. In addition this roof orientation maximizes natural comfort because the overhang allows low-angle sunlight through large south-facing windows in the winter and shades high-angle sunlight in the summer.
One ultra-efficient ductless heat pump is all the ultra-efficient 1,680-square-foot home needs for heating and cooling.
The home has energy-saving attic perimeter insulation thanks to raised heel trusses that provide added depth for an ultra-efficient 24-inch layer of R-86 cellulose insulation that completely covers the attic floor all the way to the edge.
Comprehensive draft protection is achieved by sealing all of the plywood sheathing seams with tape then covering the home with two layers of rigid closed cell foam board, which forms a continuous exterior thermal blanket.
The complete dry-by-design wall system includes draining house wrap between the two layers of rigid foam board, taping the seams of the second foil-faced layer to form a water barrier, and installing furring strips to provide an air gap between the insulation and the siding.
The ultra-efficient foundation insulation includes R-28 of rigid foam at the perimeter and 18 inches below grade.
A slab foundation was added next to the existing uninsulated staggered-height basement, doubling the size of the home’s original footprint. The new slab was poured over an ultra-efficient R-55 rigid foam foundation insulation.
The enhanced comfort floor insulation includes 2.5 inches of closed-cell plus 5.5 inches of open-cell spray foam in the floor joists above the existing basement as well as the thick rigid foam layer under the newly poured slab foundation.
Taping the plywood sheathing seams is one step in the comprehensive draft protection scheme.
The taped plywood seams in the cathedral ceiling serve as part of the advanced home sealing strategy.
"This past winter … our highest monthly heating cost was $60, whereas my neighbors were spending hundreds if not thousands per month."
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"This past winter was exceptionally cold, yet our highest monthly heating cost was $60, whereas my neighbors were spending hundreds if not thousands per month. The energy performance … is not only a great personal benefit, but also a great social benefit because we are doing our part to help our community lower its energy footprint."
– Homeowner and builder Mike Trolle