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The Basics of Insulation

Find out why insulation is so important in the construction process.

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The term insulation refers to any material that's used to slow the transfer of heat and air, but while heat and thermal management are the most commonly known functions of insulation, there are a few others of which you need to be aware.

The Basics

There's a lot to know about insulation, including the different types and ways to install them. But here are a few basics.

There are fundamentally three functions that you want from insulation:

First is thermal properties. This is the ability of the insulation to moderate the flow of heat from outside to inside or vice versa in the cooling season. In order to rate the thermal performance of insulation products, experts use what are called "R-Values," which means everything in the home is resistant to heat loss and heat gain, which are the R values. R value is a measure of resistance of heat flow through a material. The higher the value the more resistant to heat flow the insulation will be.

Note: The Department of Energy has recommended R values for all the different climates areas in the United States.

Second is how it deals with air leakage. This is where the concept of creating a building envelope (more information, below) is important. The air leakage that builders are concerned with occurs through gaps, cracks and holes around piping and wiring. To properly insulate a home you need an air-barrier system. Typically in a home, 40 percent of the heat loss or heat gain comes from air infiltration.

And third, how does it deal with moisture management in the walls and roof assemblies. A home can get moisture in the wall from several sources. One of the most obvious, of course, is rain. You want to put on the right amount of insulation so the moisture that's in the wall cavity won't condense. You also want a good enough barrier on the external side that the moisture or the bulk water can't get in there from the rain.

A properly insulated home that fulfills all three of the above functions can save you anywhere from 30 to 50 percent on your energy bills. For this reason, it's important to understand the three functions of insulation thoroughly.

Note: Another thing you should look for when insulating your new home is to make sure that all parts of the house are insulated.

What Is the Building Envelope?

All of your insulation products working together will form the insulating system, or as builders sometimes call it — the "building envelope."

The building envelope is that area of construction that's between the inside and outside of the house. Typically it's the exterior walls, roof, basement and basement floor.

A tight and efficient building envelope will keep the heated and cooled air inside by plugging up any gaps or cracks in the building envelope.

Talk with your builder about the type of insulation or moisture barrier that will work best for your home, especially if you live in areas with heavy rainfall.