DOE Tour of Zero: Shenandoah Circle by Mantell-Hecathorn Builders
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Mantell-Hecathorn Builders built this 3,841-square-foot home in Durango, Colorado, to the performance criteria of the U.S. Department of Energy Zero Energy Ready Home (ZERH) program.
The two-story home plus finished basement is expected to save its homeowners $5,500 a year in energy costs compared to a home built to the 2003 International Residential Code.
The home has ultra-efficient, triple-pane, aluminum-clad, wood-framed windows that have an advanced technology coating to minimize heat loss.
All of the home’s appliances are ENERGY STAR rated for energy and water savings. To help ensure air quality, the home meets the criteria of the EPA’s Indoor airPLUS program including cabinets, finishes, and paints certified low-VOC, no-added-urea-formaldehyde, and nontoxic glues and mastics. An energy recovery ventilator ducted separately from the furnace is operated continuously for a month prior to occupancy to help remove any residual contaminants from construction.
A hot water recirculation system with occupant controls speeds water from the high-efficiency storage water heater to faucets to reduce wasted water down the drain waiting for hot water and to improve the hot water heating efficiency.
All of the bathroom fixtures are EPA WaterSense rated for water savings.
A vapor barrier separates the footing from the insulated concrete form (ICF) foundation walls to keep unwanted ground moisture from entering the home.
ICF blocks stack and stay in place, creating the insulating “form” for the poured concrete below-grade foundation walls and wrapping the basement in a continuous blanket of R-22 insulation.
Under the 4-inch poured concrete slab, the builders installed 8 inches of crushed rock into which a perforated passive radon venting pipe had been installed. Over the rock, they laid a 15-mil vapor barrier and 4 inches (R-20) of rigid foam to prevent cold floors in winter.
The home incorporates lumber-saving advanced framing techniques that allow more space in the walls for the blown fiberglass insulation and eliminate wasted wood. Techniques include 2-by-6 studs placed 24-inch rather than 16-inch on center, 2-stud rather than 3-stud corners, and ladder blocking that provides space for insulation at intersecting walls.
The high-efficiency comfort system includes a 96% efficient gas furnace and 13 SEER air conditioner with all ducts located in the conditioned space of the home.
Spray foam insulates the top plates and air seals them to the ventilation baffles. Two inches of closed-cell spray foam also seals the inside of the walls, while an additional 3.5 inches of blown-in fiberglass fills the wall cavities.
The living room’s vaulted ceiling is air sealed with spray foam and additional fiberglass is blown in to fill the ceiling rafter cavities.
After spraying the 2-by-6 wall cavities with 2 inches (R-13) of closed-cell spray foam, the walls are covered with netting and an additional 3.5 inches of fiberglass (R-13) is blown in. This, combined with the 2 inches of high-density expanded polystyrene rigid foam on the exterior of the walls, results in a complete thermal blanket rated at R-36.
Mantell-Hecathorn used a coated wall sheathing product. This sheathing provides an airtight covering over the walls when the seams are sealed with a proprietary tape. Two inches of rigid foam was installed over this sheathing.
Over the coated sheathing air barrier, the builder installed a continuous exterior thermal blanket of 2-inch-thick rigid foam and then covered this with a yellow mesh rain screen layer for dry-by-design walls.
The dry-by-design walls use a yellow plastic mesh rain screen over the rigid foam to create an air gap that effectively drains any water that gets past the exterior siding. Dry-by-design roof construction uses peel-and-stick ice and water shield on the bottom 4 feet of the roof and also at roof-to-wall intersections. The durable fire- and pest-resistant standing seam metal roof also provides for easier attachment of the solar panels that does not require holes in the roof.
“The cost of propane to heat the house … has only been about $350 from July through May! Pretty remarkable for a 3,800-square-foot home in this climate!"
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"We wanted to have a very well‐built, energy‐efficient home for our new residence in the mountains of Durango, Colorado. Our electric bills have been zero (we actually have a net credit due to our photovoltaic system). The cost of propane to heat the house … has only been about $350 from July through May! Pretty remarkable for a 3,800-square-foot home in this climate!"