What Does R-Value Mean?
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.
The R-Value of Common Building Materials
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
Comparing Thermal Resistance of Brick and Brick Veneer Walls
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.
Installing Brick Veneer Can Give You an Opportunity to Improve Your Energy Efficiency
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:
- Canyon Ledge
- Castle Stone
- Country Ledge
- Natural Ledge
- Quartzite Ledge
- Rustic Wilderness
- Timber Ledge
If you’re interested in learning more about thin brick veneer, visit on of our locations, or read more here.