Insulation R-Value Recommendations By Zip Code

R-value is a measure of thermal resistance. This term is commonly used in the construction and building industry to show the effectiveness of fiberglass and other equivalent types of insulation. Here's a brief description of how it applies.

A particular unit of thermal resistance (R-value) is expressed as the thickness of a material divided by the thermal conductivity. Based solely on this, the thicker the material the higher the insulation R-value is.

Areas of the country that are cooler or are more concerned with their heating bills rather than their cooling bills have more thermal conductivity than areas of the country where cooling cost concerns are more prevalent, the South.

Look at these two simple equations. In Michigan, for example the outside temperature in January is -5° F. The homeowner wants the inside air temperature to be 70° F (70 - -5 = 75° difference). In Las Vegas the outside temperature for example is 105° F. The homeowner wants the inside air temperature to be 65° F. (105 - 65 = 40° F)

There is more temperature exchange (thermal conductivity) in the Northern example. This is why R-value recommendations or the thickness of fiberglass and equivalent insulations are higher in more northern or cooler climates.

And so, The Department of Energy through Oak Ridge National Laboratory in Tennessee keeps a nifty page on their website that gives recommended R-values based primarily on your zip code. It also takes two other criteria into account, whether the house is new or existing and what type heating fuel is being used.

After selecting these three criteria, click on "get recommendations". A new page will open and R-values for many different insulation locations within the home are given as well as some helpful notes all specific to your zip code.

This quick page is a great reference before beginning any insulation project. Always check with your local building code department for any questions you may have or for the latest information.

Here's the link for the Department of Energy's R-Value Calculator.

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