If you’re considering a home insulation project, you’ve likely encountered the term “R-value.” This term is commonly used when talking about insulation, but it is not always well-understood by homeowners.

The R-value scale measures the thermal resistance of a particular material. In the construction and building trades, it is used to describe the insulating effectiveness of a material. When deciding what type of insulation your home needs, along with how much insulation is necessary, it is important to consider insulation values.

Understanding the R-values of Insulation

R-value describes a material’s resistance to heat flow. The higher a material’s R-value, the greater the amount of insulating possibility.

R-value is based on a number of factors, including:

• Density of the insulation
• Insulation material
• Thickness of the insulation.

When you purchase insulation in the United States, its R-value should be printed on the packaging. However, duct and pipe insulation aren’t required to be labeled with an R-value.

Different types of insulation can have the same R-values. Rigid insulation, spray-foam insulation and fiberglass batts with an R-value of 40 all have the same insulating capabilities.

What R-value Do I Need?

The R-values for home insulation depend on where you live. The U.S. Department of Energy publishes recommendations for R-values based on climate. In addition, your local building code may require a minimum R-value. The R-values required by local codes are often lower than those recommended by the Department of Energy.

If you live in a mild climate and want to insulate your attic, an R-value around R-38 may be sufficient. But if you live in the northern part of the United States, you may need insulation with a value of R-49, or perhaps as high as R-60.

Your home’s structure will also affect your insulation decisions, as will the type of heating system you have. Cathedral ceilings, for example, usually require insulation with a higher R-value than walls. You will also need to select insulation with different R-values for different areas of your home.

Insulation and R-value: Things to Know

In general, R-value measures insulation’s ability to reduce heat loss through convection.  R-value may also indicate how well the insulation will prevent heat loss or gain through conduction and radiation.

Compressing insulation will reduce its R-value. If you are adding additional insulation to your home, be careful not to compress existing insulation, and do not try to squeeze too much insulation into a small space. However, you will want to make sure that your insulation is well installed. Gaps in insulation and other air leaks will significantly reduce the overall effectiveness of your insulation.