Brick and energy efficiency, Part 2: The Cavity Wall
/In our last post, we discussed how the thermal mass of brick slows the transfer of heat energy, allowing brick buildings to perform with much greater energy efficiency than the R-value of the material would predict — better even than most other exterior materials with higher R-values.
But, thermal mass isn’t the end of the energy efficiency story for brick walls. Modern brick installations come with an additional trick up their sleeves — the cavity wall. A “brick wall” could more accurately be called a “brick system.” In most cases, the fired clay brick that we all know and love serves as a veneer on the exterior of the wall system, layered over a structural component (often wood or or steel studs and plywood sheathing) that actually bears the physical loads the building is subjected to.
Between the brick and the structural wall lies the secret sauce of the system…space. Just space, one to several inches of it, filled with nothing but air and a few pieces of hardware that span the cavity to tie the brick on the front to the structural wall. Air is a great insulator, and when paired with the thermal mass of the brick veneer, the wall system as a whole outperforms the competition on the energy efficiency front.
But that’s still not the end of the story! The cavity that is incorporated into most brick walls also lends the flexibility to incorporate even more insulation. By designing for a slightly wider cavity, an additional layer of continuous rigid insulation can be accommodated in the air space, doubling down on the benefits of the brick wall system!
For more details on designing an energy efficient building envelope with brick, click the buttons below to access great technical resources from the Brick Industry Association.
Standard cavity wall construction - Air space shown between brick veneer and structural components, with Ties connecting the two.
Cavity wall with additional continuous insulation in the air space.
Thermal Imaging of Tie Locations. Wall ties are often blamed for causing poor thermal performance, but The maximum temperature difference shown by the colors in the image indicates a range of only about 1.5 degrees Fahrenheit.
