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Insulation and R-Values

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Insulation is a category of materials used in homes and other buildings to help them retain heat (or more technically, to help them resist the flow of heat).

The effectiveness of insulation is measured by its "R-Value". The higher a material's R-Value, the better it resists the flow of heat, and therefore, the better it insulates the building. For example, R-19 insulation retains heat better than R-11 insulation.

How can I determine the R-Value of my insulation?

In those areas where insulation is exposed (typically in attics or basement floor joists) you have several options:

  1. The R-Value may be printed on the insulation backing. You may be able to simply read its value.
  2. You may be able to estimate the R-Value based on the thickness of the insulation. The most common materials sold for wall and ceiling insulation provide air-based insulation. That is, the materials trap air in tiny pockets, and the air provides the insulation. Each inch of thickness of your average air-based insulating material provides an R-Value of about 3. Therefore, a 3.5-inch thick batt of (average air-based) insulation provides an R-Value of about 11. A 6-inch thick batt of insulation provides an R-Value of about 19.
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