Insulation Basics

Insulation is any material that restricts heat flow. It comes in a wide variety of materials, including mineral, organic, fibrous, and reflective, and in many forms, such as batts, blankets, loose fill, rigid and foam. Insulation is installed in homes to reduce heat flow through the home's envelope, keeping heat in during winter and out in summer. Considering that in most parts of the country, almost half of the home's energy dollar goes to heating and cooling, improvements to the envelope are often good investments. Even though insulation materials themselves do not use energy, or heat or cool, they have a big impact on home energy bills and comfort.

If you currently have little or no insulation and you have already sealed air leaks with caulk or weather-strip, adding insulation may be the most cost-effective energy improvement you can make. However, adding insulation to an existing home can be difficult and fairly expensive, so take time to evaluate your home carefully, learn a little about insulation and get advice and estimates from experts. An energy audit may help you prioritize measures, so view the Audit section of this program if unfamiliar with them.

One of the first principals of insulation is (if your home already has some insulation) adding more does not have the same impact as installing some in a home that has none. This is known as the diminishing return on investment in insulation. However, the addition of five inches of fiberglass saves 80 percent of the insulating potential. Additional inches don't save as much because most of the savings has already been achieved. The concept is easier to understand if you think about dressing for cold weather. The first coat you put on makes a big difference in your comfort, but if you put on more coats, each subsequent coat makes less difference.