Insulation 101 / 05.19.17 So what’s R-value anyway?

We get that a lot. What it means is “Resistance-value,” and the number after the R tells how well a material keeps heat from flowing through it.

R-value is a term that’s been around since the late ‘40s, and it’s an essential tool for anyone working on an insulation project. There are three nuggets to remember:

  • The higher the R-value, the greater the insulation power — plain and simple.
  • But, you might not necessarily need to be the king of the hill with the highest R-value. It mostly depends on geography and local building codes, but also on things like home style (houses with high cathedral ceilings need a higher R-value) and wall vs. roof (we’ll cut to the chase: the attic needs a higher R-value).
  • There’s more to consider than just R-value. For instance, cellulose insulation gives you benefits including noise control and fire resistance on top of energy savings.

Tell me more, you say? OK, here goes.

Suggested R-values for residential homes in the U.S. range from R-30 to R-60. The country is organized into zones 1–8, with Zone 1 being the warmest and Zone 8 being the coldest. Only the southernmost tip of Florida is Zone 1, where the mild climate requires an R-value of just 30, and there are only a few corners of Alaska that are as cold as Zone 8, which would require an R-60 value. 

But the truth is, you don’t need to know any of this. You can just look on the R-value map, courtesy of the Department of Energy, to find your region’s R-value. And then you can just use our Insulation Calculator to figure out how many inches of insulation will get you to your R-value goal.