Insulation is perhaps the single most important element in constructing an energy-efficient envelope, and the majority of pre-existing homes in America are currently under-insulated. Before adding insulation to your home, however, it’s important to understand what insulation is, where it should be installed and to do some research about the variety of insulation choices that now exist.
Insulation is rated by its “R-value”, which indicates how well the material resists heat transference. The higher the R-value, the more effective it is. Proper installation is vital for its effectiveness because issues such as gaps and shrinkage or exposure to moisture will reduce the R-value.
Historically there have been few alternatives to the foam and fiberglass types of insulation. Although alternatives now exist, improved versions of the foam and fiberglass types are still the most common forms of insulation used today. Advances in fiberglass (the pink stuff we recognize from attics) include the elimination of formaldehyde as a binder and use of post-consumer recycled glass in its construction. Fiberglass, however, is made with glass fibers that can break off and be inhaled and it is important to have this kind of insulation professionally installed. Foam insulation starts as a petrolum-based liquid that’s sprayed or poured into a wall cavity and then expands to fill every nook and cranny. Advances in foam insulation include the replacement of a portion of the petrolum with soy, corn fructose and other botanical sources. Other eco-friendly alternatives to fiberglass and traditional foam include wool, cotton, cork and recycled plastic. However, there may be a trade-off in terms of R-value with these products, so it’s important to do your homework and weigh the variables before choosing an insulation product.
The amount of insulation needed depends on your climate, the section of the house being insulated and the type of HVAC (Heating, Ventilating & Air Conditioning) system that you have. An energy-efficient, tight envelope requires proper insulation from the foundation up and includes:
- Foundations: basement, crawl space or slab
- Exterior walls
- Ducts in unconditioned spaces
- Attic spaces
Local building codes usually specify minimum insulation requirements, but achieving an energy-efficient home generally requires exceeding the minimum code. The US Department of Energy provides an online Zip-Code Insulation Program that provides information on recommended insulation amounts based on the climate in which you live.