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 9:12 AM ET
Edited Nov 30, 2012 10:02 AM ET


2 Answers

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

Closed cell spray foam will get you there.

Answered by Michael Maines
Posted Nov 30, 2012 9:45 AM ET


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 12:09 PM ET

Other Questions in Green building techniques

Exterior Detail Between Poured Porch/Cold Cellar and Main Floor?

In Energy efficiency and durability | Asked by Lance Peters | Mar 16, 18

Tiling around shower tips

In Green products and materials | Asked by MichaelBa | Mar 17, 18

What should I use to replace moldy fiberglass batts in exterior bathroom wall?

In General questions | Asked by Michael Schonlau | Mar 17, 18

Under insulated roof

In Energy efficiency and durability | Asked by Randy Williams | Mar 15, 18

Greatest (new) thing in air sealing?

In Green building techniques | Asked by andrew c | Mar 16, 18
Register for a free account and join the conversation

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