An R-12 Wall is an R-12 Wall No Matter the Material
Originally published by: Fine Homebuilding — July 23, 2019
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There is more than one way to build an energy efficient wall assembly using spray foam as a key component. Even though spray foam is a fairly new product in the construction scene, it is clear that changes to the energy code combined with a sustained desire for continuous insulation and air tight wall construction will allow spray foam to quickly become a common application. There are a variety of ways to install and integrate spray foam into a building assembly. For additional insight, please review the approach taken by energy-efficient building expert Bruce Harley from Vermont.
Spray foam can be a great material, but understanding its use is often hindered by overeager installers who emphasize the magic rather than the real properties of the products. Too often, I hear from clients that “my dealer said that I only need 2 in. to 4 in. of foam in my walls because it performs just like r-40 fiberglass and prevents any possible moisture problems.” It’s just not true. An r-12 wall is an r-12 wall, no matter what the material is. Cutting air leakage saves energy, but it doesn’t make up for a low r-value. For best performance, I use spray foam in a variety of ways when designing the shell of a home.
For additional information and commentary on the effects of insulation, please read the following articles:
- Thermal Insulation Topical Library
- Energy Code Math Lesson: Why an R-25 Wall is Not Equal to a R-20+5ci
- Wood Framed Wall Insulation Calculator Explained
- Perfect Walls are Perfect, and Hybrid Walls Perfectly Good
- Fear Building Envelopes No More with This Website & Videos
- Polyiso CI Helps Designers Achieve a 'Perfect Wall'
- An R29 Wall Is More Energy Efficient When Built As R20+5ci Why?