Q: We’re required by code to have an R value of 26. If I were to use Concrete Masonry cavity wall construction, the wall will be way too thick. Help!
-Cavities Always Lead to Efficient Buildings
Dear CALEB:
A structural Concrete Masonry back up wall with an Architectural CMU veneer is a great choice for resilience, fire resistance, thermal comfort, water penetration, and durability. An essential component of a cavity wall is, well, the cavity. The cavity includes a space for ventilation and drainage as well as providing a place for continuous insulation. I agree that if you were required to have an R-value of 26, it would make the cavity exceptionally wide, but a major benefit of using a CMU cavity wall is its thermal mass. In the 2012 IECC for climate zone 5 (Massachusetts), the prescriptive R-value requirement for a mass wall is 11.4. As you can see, the code takes into account the benefits of thermal mass, allowing for less insulation. Different wall systems have different requirements. A metal building requires an R-value of 26 and a wood framed structure requires an R of 20. The amount of insulation required for a mass cavity wall is much less than that of other systems, reducing insulation cost and the space required. Occupants are toasty in the winter and cool in the summer. BTW, I grew up in a block house and we never needed AC in the summer… hmmmm – I wonder if thermal mass walls can help to lower HVAC loads?……. to be continued
Heidi Jandris grew up immersed in all things concrete block. As a kid she helped her dad build block walls and as an adult worked by his side as a welder. She received a Bachelor of Architecture degree from Pratt Institute and a Masters of Sustainable Building Systems degree from Northeastern University’s College of Engineering. She is part of the 3rd generation of her family’s business. She provides technical services to the design community while researching and implementing ways to improve the efficiency and lower the environmental impacts of their products.
