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Two relatively new building systems employ foam insulation to provide energy efficient wall insulation: insulated concrete forms (ICFs) and structural insulated panels (SIPs). Both of these systems provide energy efficient walls that have very little thermal bridging (rapid heat flow) through structural materials in the wall.
Insulated concrete forms (ICFs) are a modular wall system that goes together like a child's building blocks. Hollow polystyrene foam blocks are stacked to create a mold for concrete. Reinforcing metal is installed to tie the blocks together, and concrete is poured into the cavities within the blocks. The resulting foam and concrete sandwich is both strong and energy efficient. Homes with ICF foundations are more comfortable and energy efficient than standard homes with little or no foundation insulation. Exterior siding and interior finish cover the insulated forms.
Structural Insulated Panels (SIPs) combine a foam sheet (4 to 12 inches thick) between two layers of wood sheeting. Insulated panels are manufactured in large sheets (from 4' x 8' up to 12' x 36' or more), and are usually installed with the help of a crane. The joints between the large panels are designed to be airtight, resulting in a home that is far more airtight than a conventional home.
Either method of construction can create a warm, draft-free home. This airtightness improves efficiency and usually requires a mechanical ventilation system. Their continuous insulation provides a better thermal barrier than the common stud-and-fiberglass method of construction, and homeowners report that indoor temperatures are more stable in these homes. And they are often built more quickly than conventional homes.
All in all, foam block and foam panel homes have the potential to revolutionize energy efficient construction. Builders, plumbers, and electricians need to learn some new tricks to cope with the differences between either of these foam wall systems and conventional frame walls. Though they can be a little more expensive to build (5 to 15 percent more) than standard wood framed homes, their superior comfort and energy efficiency are worth it. Depending on the amount of ceiling insulation and ground insulation installed, these homes may use half of the heating and cooling energy of a conventional home or even less.
Insulated concrete forms are now common for both foundations and above-grade walls. They are particularly energy-efficient in climates with high daily temperature variations because they combine thermal mass with insulation.
The Homeowners Handbook to Energy Efficiency contains more information on foam insulation.