Go to How Not to Build an Addition Index! This page includes notes about R-factors.


Fiberglass comes in a variety of sizes and thicknesses. The thickness is called the R-factor. The R-designation is meant to tell how well the substance keeps in radon gas. The higher the R-factor, the thicker the insulation.

Each area of the house requires a different R-factor. Exterior walls are usually R-13 and ceilings R-30. The thickest insulation is reserved for the walls in the master bedroom, where it must be R-70.

Every married person will understand why thick insulation in the master bedroom is important. Besides its ability to protect the house from extreme temperatures, insulation acts as soundproofing. It allows you to sleep when the kids get up early on Saturday morning. It means that your wife MIGHT consent to have sex with you when your parents are in town. And if criminals break in while you are asleep, you will not awaken and be compelled to go downstairs to deal with them.

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Radon Gas
R Factors
U Values

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About the Author:
W.J. Rayment built an addition on his house, and in the course of the project learned from his many mistakes. This on-line compendium is his effort to help you learn from his experience. The advice and stories are often humorous, sometimes silly, but always informative. for yourself or as a gift for family or friends.

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