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
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
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Heidi Jandris is a technical expert and trusted voice of the industry. She part of the family business’s 3rd generation, grew up immersed in all things concrete block and worked as a welder at the plant before getting her BArch at Pratt Institute in Brooklyn NY. She is the Sustainability Manager and provides technical and design services for A. Jandris & Sons.