Brrrr! Brick and energy efficiency, Part 1: Thermal mass
/It’s cold outside. Really cold where this blog originates. Seems like a great time for a series of posts on energy efficiency and sustainability!
Do you know about thermal mass?
Seems like everyone understands at least a little bit about R-Value. It’s simple and straightforward. As the R-Value of a material goes up, the insulative value goes up, so a material with a high R-Value must be energy efficient and one with a low R-Value must not be, right? Not so fast!
A typical exterior building wall clad in brick (a material with a relatively low R-Value) reduces heat gain on the interior of the wall nearly 50% in summer. For comparison, a wall clad in EIFS (a high R-Value synthetic stucco imitation) reduces heat gain by only 31%. Walls clad in vinyl siding reduce heat gain by 15%, and fiber cement board walls only by about 10%. In the winter, a brick wall reduces heat loss to the outside by 55%, whereas EIFS performs only at 33%, vinyl at 18%, and fiber cement at 11%.
How can this be? Thermal mass. The “weightiness” of clay brick stores heat and dramatically slows its transfer through the wall. Heat energy is constantly trying to flow from one side of the wall to the other to make the temperature on both sides the same (equilibrium). It takes so long for this to happen in a brick wall that the natural day-night changes in outside temperature can cause the direction of heat transfer to reverse before much energy is lost. As a side benefit, this delay in releasing energy means that building HVAC systems run less frequently and operate during off-peak hours when energy costs are lower. (Check out the Brick Industry Association’s excellent Builder Note and Technical Note on this topic for a more detailed explanation.)
But, it’s not just about the brick. The wall system engineered to complement clay brick veneer plays a big role in a brick structure’s energy efficiency. More about this in Part 2.
