Q: Is continuous insulation required to meet the energy code?
-Continuous Insulation Myth Busted Again
It is not. There are several options to pass the energy code; prescriptive, trade off (COMcheck™) and whole building analysis. Within the prescriptive method there are 2 tables which can be used to pass the code, the R-value and the U-factor table. Only the R-value table has the CI requirement. Why you might ask? This table considers the insulation performance only and not the other components of the wall assembly. While this is the simplest way to pass, it is also the most restrictive. The U-factor table considers the whole assembly, including the insulation, and offers a bit more flexibility. For a typical assembly with 4” CMU veneer, 3” of rigid insulation (R-15) and an 8” LW block backup, adding up R-values of the elements (including the air space, drywall, etc.) gives us an R-value of around 19.06. Taking the inverse, the U-factor ends up being .052. The IECC 2012 & 2015 climate zone 5 requirement for mass walls is a U of .09 (R-11.11). This wall assembly will exceed the energy code by 70% and have an overall thickness of 16”. To get the same thermal performance out of an assembly without thermal mass benefits (steel & wood), more insulation would be required. Less thermal mass equals more insulation… and it would not have the resiliency of a mass structure. Other ways to pass the energy code without the CI requirement are the trade-off method (COMcheck™) and whole building analysis. These methods offer more flexibility and also do not require continuous insulation. More next time….
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.