Hello, I have a space that about 3/4" deep that I want to put some rigid insulation. I plan on using either some 1/2" xps or isocyanurate (not Thermax brand... i.e. not fire rated) i have laying around. I know that it needs to be covered and is usually recommend that at least 1/2" drywall should be used. I don't have that much space so I am try to find some other material that is 15 minute fire rated. I was thinking sheet metal or some aluminum I have left over from doing facia. Does anyone have any ideas or links to a list of suitable materials? I know it's not a big space but R-3 or 4 is better than R-0.

Thanks!

 

Your space is 3/4" deep, but what is the area? If this is just a crack you are filling, R-value is not important, simply use a caulking or foam backer rod.

Describe the area in question.

Bud

 

Hi, thanks for the reply. No the area is not a crack. It is the inside of a built in dresser I'm building but it is on an outside wall. I would like to insulate between the wall and the drawers.

 

Hi, is there any insulation in the wall at all, or is this r-3 or 4 going to be it?

There is another fire rated covering option, a fire rated paint. I have seen a couple of products advertised.

In your climate, you will want much more than this thin layer between inside air and outside cold temps. The example I use is a closet on an outside wall. Even though the wall may be insulated, a closet will most often not have a source of heat, and once the door is closed, the exterior walls will get cold. At that point, condensation can occur and mold may form on those closet walls, even though the outside walls are insulated. With your built in dresser, there is a similar potential of isolating that surface from the heat and exposing it to moist inside air. By having a lot of insulation, you increase the surface temperature even with a limited amount of access to heat and thus reduce the moisture potential.

Bud

 

Yes, there is a properly kraft faced insulated framed wall on the other side with 1.5" Thermax with taped seams between the sheathing and siding as a thermal break. Condensation is not an issue. I just like to over do things. I'm shooting for a near super insulated home. I have the foam board laying around and I'd like to use it here.

Any other options besides paint? What do you think of the sheet metal/aluminum idea? I'm leaning towards these materials as I have them and obviously they don't burn. Are they acceptable? If not do you know of any comprehensive lists of approved materials?

 

We are instructed to use sheet metal for covering large gaps to create a fire break so they should work fine.

As for a comprehensive list, my guess for a starting place would be the appropriate fire code. Unfortunately, codes vary depending upon location and local preferences. As an example, the paint approach mentioned has been approved by our state fire marshal for use in plenums for commercial construction, which should be a more critical application. Yet some local code officials will not allow it for protection on rigid foam over basement walls. When in doubt, check locally.

As for super-insulated, I'm going that direction as well, however, even being an energy auditor, there are some pit falls to watch for. Don't hesitate to ask.

Bud