0 Helpful?

How do I get an R-20 wood wall?

Insulation method to get R-20 in a 2x4 framed wood stud wall?

Asked by Diego Gutierrez
Posted Nov 30, 2012 8:12 AM ET
Edited Nov 30, 2012 9:02 AM ET

Tags:

2 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.
1.
0 Helpful?

Closed cell spray foam will get you there.

Answered by michael maines
Posted Nov 30, 2012 8:45 AM ET

2.
0 Helpful?

Closed cell spray might get you to R20 center cavity, but the severe thermal bridging of 3-3.5" studs brings the whole-wall performance down to R11-12, even at a full 3.5" depth, and including the gypsum & siding. By contrast a full 3.5" of cellulose or open cell foam is still in the R9.5-10 range, a difference that could be made up with half-inch rigid foam (any type) on the exterior at much lower cost.

To hit ~R20 whole-wall with 2x4 framing put 2" of rigid polyiso on the outside of the sheathing and cellulose or open cell foam in the wall cavities.

Answered by Dana Dorsett
Posted Nov 30, 2012 11:09 AM ET

Other Questions in Green building techniques

Adding wall R-value in a historic retrofit

In Green building techniques | Asked by alok khuntia | Feb 28, 15

Biggest bang for your buck?

In Energy efficiency and durability | Asked by Justin Murphy | Mar 1, 15

Floor construction for a finished basement

In Energy efficiency and durability | Asked by Andy Martin | Mar 3, 15

Do screws through exterior insulation reduce the wall R-value?

In General questions | Asked by brad hardie | Mar 1, 15

Should engineered wood flooring be glued to a concrete slab?

In Green products and materials | Asked by Christina Griffin | Mar 2, 15
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!