Spray Foam R Value

Good insulation is the key to securing the comfort of your home in addition to reducing your energy related expenses.  And in this regard, taking stock of the idea of thermal resistance of the insulatory substance you are using or are planning to use is crucial.

Thermal resistance of any substance is its capacity to resist heat flow. The higher the R-value the more effective is the insulating material in preventing outside heat/cold from penetrating into your homes. It is denoted mathematically with the letter R and has the units (m^2*K)/W.

Traditional materials used for insulating homes like fiberglass and cellulose have a low thermal resistance (or R-value) in comparison to spray foam. The R-value of any insulatory material is usually determined through the testing methods mandated by the American Society of Testing and Materials.

Now the R-value of fiberglass ranges from 2.2 to 3.2 per inch but that of spray foam is significantly higher which aids good insulation.

Insulation_Attic_Open cell spray foam insulation

Being made of cells which are not completely closed, air often fills up the open spaces which results in a lower thermal resistance. It has a thermal resistance or R-value varying between 3.4 to 4.5 per inch depending on the quality of the material used in the creation of the foam by the manufacturers. But even with its low thermal insulation capabilities, open spray foam is much better than fiberglass which as mentioned has a lower R-value.


Closed cell spray foam insulation

Unlike open cell spray foam, the cells here are enclosed completely and are filled with a gas. The foam expands and hardens to become nearly 25 times its original state. It is a great insulator since it can metamorphose into foam of various densities. It has a higher R-value in comparison to its open cell counterpart varying between 6.6 to 7 per inch depending on the materials used and the manufacturer of the foam. Closed cell spray foam successfully insulates your home against air and water vapor, prevents growth of mold, mildew and protects against invasion by insects and even discourages rodents from entering.

Better thermal resistance properties make spray foam a lucrative insulating material in comparison to fiberglass even though the cost of spray foam is a little higher than the latter.