The insulation property of building materials can be expressed as its per-inch R-Value, which indicates its degree of thermal resistance per inch of thickness. However, it is common practice for products, such as fiberglass insulation, to list their total thermal resistance as a single R-Value on the package.
For example, regular fiberglass insulation has a per-inch R-Value of about 3. Therefore, fiberglass batting insulation 3.5 inches thick has a total R-Value of R-11. R-Value is a linear value, so if you double the thickness the R-Value doubles.
These values depend on the material having been installed according to the manufacturer’s directions of course. You cannot jam two 3.5-inch thick battings into a 3.5-inch space and expect to get R-22. In fact, if you did that, you would probably get less than the original R-11 of thermal resistance of a single batting.
Here is a list of rounded per-inch R-Values of various common building and insulating materials plus the total R-Value of products made from these materials:
Brick – 0.2 per inch – R 0.72 for a common face brick wall
Wood – 1 per inch – R-3.5 for a 2 x 4 stud
Fiberglass or cellulose – 3 per inch – R-11 for 3.5 inches
Compressed fiberglass – 4 per inch – R-14 for 3.5 inches
As you can see, brick on its own is not the greatest insulator. A common 3.625-inch thick brick does not even reach R-1. Brick homes are typically constructed of two walls with an air space in between for moisture drainage. Air is a better insulator than brick, but not by much. An inch of still air provides about R-0.44.
Therefore, a double brick wall with 2 inches of air between them and interior plaster would provide no more than R-3 of insulation. Brick has other desirable properties- it’s beautiful, durable, and maintenance free- but as a thermal barrier it falls short.
When brick veneer is installed, the homeowner has an excellent opportunity to increase the total R-Value of the exterior walls after the old siding is removed. Foil-faced polyisocyanurate insulating sheets can be installed directly to the sub-siding. This type of insulating board comes in thicknesses from one-half to 2 inches thick. Each inch of thickness provides an additional R-6.5 of insulating power. Even a less expensive, thinner foil-faced closed-cell foam sheet beneath the brick veneer will significantly add to the home’s thermal resistance.
Some of the most popular brick veneer options are:
If you’re interested in learning more about thin brick veneer, visit on of our locations, or read more here.