Continuous Insulation, Part 1 – GreenBuildingAdvisor – GWC Mag

by gwcmag
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Living in a cold climate, where it’s not uncommon for wintertime temperatures to reach -20°F, you would think contractors and homeowners in my market would be excited to use continuous insulation (CI) on every new home being built, and for every existing home having the exterior cladding replaced. I rarely see either of those things happening.

Part of the reason is that Minnesota state and local building codes don’t require CI. Cost is another factor. As both homeowners and builders become better educated on the benefits of CI, this should start changing. I’m advocating for its inclusion on projects I’m involved in.

There are many reasons to use continuous insulation. Reduced energy consumption—often touted as the primary benefit—is key but I view lowering heating and cooling costs as secondary to improving thermal and sound comfort and increasing durability. In this post, the first in a three-part series, I will talk about building code requirements and building science principles pertaining to continuous insulation.

IRC on continuous insulation

Building codes have begun to align with building science and we are seeing more areas across the country adopt continuous insulation as part of the energy code. CI requirements with regard to the energy code can be found in the 2021 International Residential Code (IRC), Chapter 11, “Energy Efficiency.” In this post, I will be referring to the prescriptive code path because that is what most contractors use to meet continuous exterior insulation requirements. There are other compliance paths such as total building performance and energy rating index options, which allow for some tradeoffs.

Table N1102.1.3 IRC
Table N1102.1.3 (R402.1.3) Insulation Minimum R-Values and Fenestration Requirements by Component (2021 IRC)

The yellow highlighted area in the table above shows the different R-value possibilities for wood-framed walls based on climate zone. Climate zones 1,…

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