If your building has walls and a roof, then it has wall-to-roof intersections. The details at these intersections, or what could be called the “corners of the envelope,” vary from project to project. They need to be well-designed for acceptable structural performance but can sometimes be challenging to control both convective and conductive heat flow. Let’s take a look.

Continuous convective resistance — the air barrier system — can be confounded by penetrations for roof edge blocking support, parapets, corbels, and perimeter projections such as sunshades. How to affect a continuous airseal varies with the details, but usually transition tape, sealant, or mastic is needed.
Conductive resistance can be compromised by thermal bridging of elements that pass through the insulation, such as roof edge angles and sunshades. One challenge is that such heat loss is difficult to quantify without using a program such as THERM that calculates the overall U-factor for the modeled section.
We have found that many designers do not realize that the Energy Code applies to the entire envelope, including the roof-to-wall intersection.

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