EcoSmart House 2012 - The Building Envelope

Structural insulated panels and insulating concrete forms comprise the envelope of the Ecosmart house in Bozeman, Mont. Combined with high-efficiency windows and doors and a technologically advanced window glazing, the house’s cooling and heating loads are expected to remain low.

ICFs were used in the lower level and main floor walls; the main level floor is constructed from an ICF floor form. ICFs, which are formwork for concrete that stays in place as permanent insulation, will provide thermal and acoustic insulation, as well as space to run electrical conduit and plumbing. ICFs can reduce heating and cooling loads by an average of 30 to 50 percent and do not off-gas.

SIPs comprise the second floor walls and roof. The SIPs consist of expanded polystyrene insulation laminated between sheets of structural sheathing. The wall SIPs are 8-inches thick with an R-value of 31.6. The roof SIPs are 12-inches thick with an R-value of 48.3. Compared to stick framing, a SIP building envelope can reduce the amount of energy used to heat and cool a home by 50 percent.

The triple-pane vinyl windows and doors have U-factors of 0.25 or lower, which reduces overall heating and cooling loads. Different glazing packages, dependent on which floor of the house and its orientation, meet solar heat gain coefficient requirements. The vinyl, which is an unplasticized polyvinyl chloride, is specifically formulated to be impact- and fade-resistant. The Washington, D.C.-based U.S. Department of Energy estimates a $125 to $340 annual energy savings for each traditional single-pane windows replaced with an Energy Star vinyl window.

The windows are fabricated with sunlight responsive thermochromic (SRT) glazing, which was designed by Jenison, Mich.-based Pleotint. The glazing has a film that tints when there is direct sunlight; the variable light transmission tint is completely sunlight-activated and blocks heat, glare and UV light. There are no wires, electrodes, power supplies or control apparatus. The windows adapt at any time of day and year based on the amount of sunlight. Research is expected to show the SRT window system to yield energy savings of at least 20 percent compared to conventional glass.

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