How Thick is R 38 Insulation?

R-values,, such as R 38 insulation, are used by the construction industry to describe the thermal resistance of insulation materials. When you are looking at an R-38 insulation, you are actually reading a description of its resistance, rather than size or thickness of the material. Determining how thick R-38 insulation is will depend upon not only its R value, but other factors such as size, use of material and weight.

R Value Insulation

To determine the R-value of a material, a range of values are taken into account, including the fabric of the item, the density of the material, and its overall thickness. The value is therefore affected by the per-inch thickness of a fabric. The R-38 fabric is usually a fiberglass or similar material, although it can also be made from cellulose, which is a make of shredded paper which is then tightly sealed into the area being insulated.

Thickness of R-38 Insulation

The thickness of your R-38 insulation will depend very much upon the material you have. The fiberglass will come in rolls, also known as batts, which are of very different sizes. For an R-38 fiberglass batt, you should see a thickness of around 6 1/4 inches. With a cellulose insulation, you should see the thickness of the finished, fitted product at around 12 inches for an R-38 insulation.