LOUISVILLE Blog

Insulation 101: What is R-Value?

Insulation 101: What is R-value

If you’ve ever heard about insulation, there’s a good chance you’ve heard it be referred to in terms of it’s R-Value.  So what is that anyway?

What is R-Value?

The “R” in “R-Value” stands for Resistance.  R-Value simply means resistance to heat.  An insulation’s R-value is its ability to stop heat from entering or leaving your home, which is what insulation is designed to do. 

What do the numbers mean?

R-value is measured per inch, so the number is telling you how well it can resist heat for every inch of insulation material that is installed. Values typically range from R0 (no insulation) to R60 (the best insulation you’re likely to find in the United States). 

How much R-value do I need?

How much R-value you need depends on what climate zone you are in and what type of room or application you are insulating.  For example, in Louisville, you likely need R38 in your home’s attic to achieve minimum code.  R49 is often recommended, and may become the standard in the area with progressing energy code changes.  Also for example, in Louisville, you likely need no insulation in your garage’s attic to meet minimum code because it is not considered a living space. That said, it is still recommended to insulate a garage attic to R38 to keep your personal belongings from freezing.

What Climate Zone am I in?

The Greater Louisville area is considered Climate Zone 4 (mixed-humid), which spans much of the lower Midwest.  See the zone map on Energy.gov’s website here: https://www.energy.gov/sites/default/files/2015/10/f27/ba_climate_region_guide_7.3.pdf

What insulation has the highest R-Value?

While different types of insulation are needed for different applications, they do range in how they can be used, what benefits they provide, and how much R-value per inch they achieve.  Closed Cell Spray Foam and Rigid Foam board insulation tend to have the highest R-values per inch across the board, but it’s important to note that the highest R-value should not alone determine if it’s the right choice for a particular job.  Some other factors include fire resistance, noise reduction, lifespan, water and mold resistance, vapor barriers, physical shape, ability to physically access the space, and of course, cost.