Remodel-Radiant Barrier In Wall Cavity Question

Repair help for the do-it-yourselfer.
For mobile home parts, click here.

Moderators: Greg, Mark, mhrAJ333, JD

Posts: 3
Joined: Sun May 21, 2017 6:18 am

Fri Jul 07, 2017 3:21 pm

Hello, all. I searched and pretty much all I saw here was radiant barriers in roofing, flooring or underbelly applications, so I thought I'd ask about an idea I have.

My MH is oriented just slightly off true North and my location is South Texas. I have no vegetation shielding the West side, so there is a lot of heat on that side. So what I was thinking about was since I'm systematically going through and remodeling the inside was incorporating a radiant barrier. The exterior walls are 2X4 with OSB/vinyl sheathing, so I've got 3 1/2" depth to work with.

Thermasheath RMAX 3 (rigid foam/foil backer) is available in various thicknesses. What I'd like to know is the feasibility of using the 1/2" RMAX 3 (R-3.2) with the foil facing the back of the OSB sheathing. Then, since an air gap is needed, use a 1" lath to keep the sheath upright. This will give 1" spacing for the air gap, so I've got 2" remaining depth in the wall cavity. Owens Corning has Foamular 150 insulation in 2" thickness (R-10), so this works out pretty neat on math. Not counting any insulating benefit of the air gap, this is (on paper) R-13.2, which is essentially what the fiberglass batt insulation provides.

My concern is will there be a breathing problem in the wall cavity with this. I don't know if there's a vapor barrier behind the vinyl siding (probably not). I'd appreciate any thoughts on this. Thanks in advance.