Providing continuous rigid insulation, or "outsulation", on exterior walls improves durability by protecting the WRB and keeping the sheathing warmer (and hence drier), and increases thermal performance by adding a clean layer of insulation uninterrupted by wood or other materials. It also improves performance of cavity insulation by covering thermal bridges from the wood studs, plates, and headers that otherwise reduce the ability of adjacent insulation to achieve its full performance.

Rigid insulation above roof sheathing has similar benefits and is one method of creating a moisture-safe unvented roof assembly.

At the foundation, rigid insulation on the inside or outside of foundation stem walls can significantly reduce slab edge losses and is one of the steps required to create a sealed, conditioned crawlspace.

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Comments (1)

Katy Hollbacher
Katy Hollbacher Beyond Efficiency

‼️ Important FYI that there's apparently a very long delay in procuring mineral wool at the moment. Thanks to contractor Joel Boisvert , building our client's Passive House in Santa Cruz, for bringing this to our attention just now! Anyone else have comments on mineral wool availability?

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