EnergyWise House: Elements of an Energy-Efficient House

Foundations and Slabs Foundation walls and slabs should be at least as well insulated as the living space walls. Uninsulated foundations have a negative impact on home energy use and comfort, especially if the family uses the lower parts of the house as a living space. Also, appliances that supply heat as a by-product, such as domestic hot water heaters, washers, dryers, and freezers, are often located in basements. By carefully insulating the foundation walls and floor of the basement, these appliances can assist in the heating of the house. Modern windows are becoming increasingly more energy efficient. Still, proper window placement is essential to minimizing a home's overall energy consumption. Credit: BobVila.com Windows The typical home loses over 25 percent of its heat through windows. Since even modern windows insulate less than a wall, in general an energy-efficient home in heating dominated climates should have few windows on the north, east, and west exposures. A rule-of-thumb is that window area should not exceed 8 to 9 percent of the floor area, unless your designer is experienced in passive solar techniques. If this is the case, then increasing window area on the southern side of the house to about 12 percent of the floor area is recommended. In cooling dominated climates, its important to select east, west, and south facing windows with low solar heat gain coefficients (these block solar heat gain). A properly designed roof overhang for south-facing windows is important to avoid overheating in the summer in most areas of the continental United States. At the very least, Energy Star rated windows or their equivalents, should be specified according to the Energy Star regional climatic guidelines. In general, the best sealing windows are awning and casement styles since these often close tighter than sliding types. Metal window frames should be avoided, especially in cold climates. Always seal the wall air/vapor diffusion retarder tightly around the edges of the window frame to prevent air and water vapor from entering the wall cavities. Air-Sealing A well-constructed thermal envelope requires that insulating and sealing be precise and thorough. Sealing air leaks everywhere in the thermal envelope reduces energy loss significantly. Good air-sealing alone may reduce utility costs by as much as 50 percent when compared to other houses of the same type and age. Homes built in this way are so energy-efficient that specifying the correct sizing heating/ cooling system can be tricky. Rules-of-thumb system sizing is often inaccurate, resulting in oversizing and wasteful operation.

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