0 Helpful?

Cold, wet sheathing on double stud wall?

The exterior sheathing on double stud walls is known gain moisture during winters. The data I've seen is all about "conventional" sheathing choices. There are several brands of fiberglass reinforced gypsum sheathing in the market, being sold as exterior sheathing, all of these products require "bracing" by other means. Denseglass is one brand and it has a moisture permeability of about 20 perms. Does use of fiber glass reinforced gypsum exterior sheathing result in a more resilient assembly than plywood?

Asked by Jerry Liebler
Posted May 27, 2014 9:51 AM ET


3 Answers

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

Yes, DensGlass sheathing is more vapor-permeable than OSB, and for that reason may be preferable for use on double-stud walls. GBA has already reported on this recommendation; in my blog titled Monitoring Moisture Levels in Double-Stud Walls, I quoted John Straube, who advised: "Choose a sheathing that is more vapor-permeable than OSB — plywood, fiberboard, or DensGlass Gold.”

Answered by Martin Holladay, GBA Advisor
Posted May 27, 2014 10:08 AM ET


The real answer to cold sheathing is NO sheathing! I've just eliminated the DensGlass too! I am planning on a "thin brick" exterior finish. Thin brick is a "moisture reservoir" cladding and Greenguard DC14 is a fan fold XPS product designed to isolate the moisture that can be driven inward from such cladding by solar isolation. I plan on using DC14 under a metal panel system designed to facilitate the thin brick installation. At least one vendor of the metal substrates has tested them attached to framing 24" OC over 1/4" foam, with no other substrate. The resulting wall's layers, from outside in are: 1/2" thin brick, Ambrico "EZ-WALL" panels, DC-14 (1/4" xps), vapor open WRB (Tyvec), 2x4 24" OC with cavities filled with r15 mineral wool, 3 1/2" space filled with r15 mineral wool, 7/16 OSB detailed as air barrier, 2x4 24"OC cavities filled with r15 mineral wool, 5/8"drywall. An r40+ wall that's 12 3/8" thick with drying both ways from the OSB which has over 2/3 of the insulation on it's exterior.

Answered by Jerry Liebler
Posted May 27, 2014 1:40 PM ET


Jerry, We had the same discussion about a year ago and you swore the real answer was fibreboard.

Answered by Malcolm Taylor
Posted May 29, 2014 8:17 PM ET

Other Questions in Energy efficiency and durability

Best building envelope approach for an owner-built home in northern Wisconsin?

In Green building techniques | Asked by Michael Sterner | Oct 17, 16

Concrete floor caulking is failing... why and how to fix?

In Green products and materials | Asked by Steve Hengeveld | Oct 21, 16

Garage and root cellar insulation

In Energy efficiency and durability | Asked by Jonathan Lawrence CZ 4A New Jersey | Oct 19, 16

Bottom edge of rigid foam on basement wall

In Green building techniques | Asked by Nicholas C | Oct 18, 16

Unventilated, highly insulated roof — replacing shingles

In General questions | Asked by Sharon Secrist | Oct 20, 16
Register for a free account and join the conversation

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