Insulation Information Sheet ~ R Value
What is R value?
R value is a rating given to insulation. The R rating is used to measure the insulations ability to resist heat flow. Higher is better - the higher the R value, the more effective the insulation is. House Insulation should not be purchased based on its thickness, rather, it should be purchased based upon the R value it will provide.
Some quick facts about R value are:
- No matter the type of insulation, if the R value is the same, they should insulate equally.
- R value performance testing is done with no leaks or air movement in a 70 F environment. However, when you need insulation the most, you're usually not in ideal temperatures or conditions. Therefore, typically the rated house insulation R value is higher than the actual effective R value.
- R value in house insulation is greatly reduced when there are air or water leaks present.
- The standard R value for house insulation varies based on climate zones (see chart below).
- Concrete and earth are great insulators. In fact, 1”of insulation equals 30”of concrete.
There are many types of house insulation materials available, each has a different R value.
Some of the most common insulation materials are:
- The house insulation R value of Blown in Cellulose Insulation = 3.70 per inch
- The house insulation R value of Fiberglass Insulation = 3.14 per inch
- The house insulation R value of Expanded Polystyrene = 4.00 per inch
For example: You live in NW Maryland, zone 2. Your attic has approximately 12” of fiberglass insulation.
Using the values above, 12 inches x a value of 3.14= 37.68
Your homes insulation value is approximately R38 which is substandard. It is time to upgrade your insulation.
Protecting Your House Insulation and its R value
Keeping your R value high is extremely important as it will improve the heating and cooling efficiency of your home. Water is one of the largest concerns with regards to R value and house insulation. If moisture/water gets into your insulation, the R value will be compromised. Moisture can weigh down the insulation leaving gaps and bare spots causing it to be ineffective.
