Super-insulated homes (also called Passive Houses or zero energy homes) use high levels of insulation to slow heat movement through the walls, ceiling, and floors of the home. They are also well-sealed to reduce drafts and control moisture movement. These features reduce the cost of heating and cooling, and improve the comfort of the home.
- The walls of super insulated homes are thicker than standard homes, allowing for 6 to 12 inches of insulation. They sometimes include sheets of foam insulation that cover the studs and other structural members to reduce heat flow through the framing itself. A ten-inch wall, filled with fiberglass batts and covered with a one-inch foam sheet, would give a total R-value of about R-35, considerably higher than the R-19 walls used in most modern homes.
- The roof and ceiling structure usually allows for up to 24 inches of insulation. When insulated with loose-fill fiberglass, this assembly would yield an average value of R-70, compared to the industry standard of R-40.
- The foundation is always waterproofed and insulated. Moisture control measures are installed to keep ground moisture out of the home.
- The windows include three or four layers of glazing, with specialized gases between the layers and low-e coatings to reduce heat loss.
- Air sealing is accomplished by installing a continuous air barrier at the ceiling, walls, and floor or foundation.
- This high-level of airtightness improves the efficiency and comfort of the home, but usually necessitates the use of whole-house ventilators to remove moisture or indoor pollutants. Super-insulated homes and passive houses employ heat-recovery ventilators that extract heat from the home’s exhaust air and transfer it to the incoming outdoor air.
The true test of a home’s insulation level and airtightness is the outdoor temperature at which the heating system must run to maintain comfort. Most standard homes need heat when the outdoor temperature drops below 60°. Some super insulated homes don’t need heat until the temperature drops below 40°F. The difference in energy efficiency between these two homes can save hundreds of dollars every year.
See The Homeowners Handbook to Energy Efficiency for more information on insulation and other home efficiency methods.