The insulation R value reveals how well a material works to prevent the loss of heat. R value is a therefore a measure of thermal resistance. R values are expressed per inch, and the higher the R value, the better the insulation property.
- Closed cell spray foam: 5.6 – 8.0
- Cellulose: 3.1 – 3.8
- Fiberglass batts: 2.9 – 3.8
As you can see, spray foam is the superior material in terms of R value. However, each insulation project is unique. In some cases, a combination of materials works best in terms of cost, efficiency and building code regulations.