Anyone know anything about aluminum insulation?

Specifically, can aluminum insultion in an older home result in stains on the drywall over time?

My mom’s living room has not been painted in over 25 years, and there are some areas of dark discoloration around the studs. She read somewhere (but can’t find it) that the insulation that they used (accordion-style aluminum insulation, according to her) can cause this discoloration. Does anyone have any experience with this, or know of any sites where I can learn about this? Google hasn’t been helpful. Since a lot of Dopers are big into home repair, I could use some advice.

I also can’t find any references to this type of insulation, used 55 years ago. Any ideas?

Drawing a total blank-o on that one. I cannot imagine aluminum being used as an insulating material, owing to its ability to conduct heat so well. Once houses began to receive insulation in the exterior envelope (late 1940’s IIRC) the materials of choice were cellulose, rockwool, and vermiculite. Fiberglass pretty well replaced those products completely by 1960.

If you’re seeing spots which fall on stud lines, then you’re likely seeing rusting of the heads of drywall nails. Beyond that, if you’d like to freshen the room and be sure that the marks don’t reappear, then repaint using a stain-sealer such as Bin 123® made by the Zinsser company. It is a white pigmented shellac which will seal in all of the nasties visible on the present wall, such that you may topcoat with any good quality latex or oil based interior paint.

Thanks for the advice. The stains are spots at the nail heads, and streaks along the seams of the drywall. It is a light gray discoloration. I’m a bit confused about this type of insulation too. Aluminum is still used in insulation, as the foil layer, but I have no idea what this stuff actually is. I only have my 80-year-old mom’s recollection. I found one website that talked about aluminum insulation corroding in contact with moisture and staining, but the reference was highly technical and for installers. The areas where the staining occurs haven’t had any water damage that we can see. We’re not sure what this really is…just my mom saying she read somethings about it who knows when or where, so of course she insists that this IS what is happening.

Any other ideas?

Sometimes the discoloration at the stud locations is due to differences in condensation. The bay between the studs is generally warmer than the studs themselves. Moisture condenses on the drywall at studs moreso than the drywall over the bays. Over time this can result in discoloration.

This will happen to some degree on any outside wall in a cold climate, but the type of insulation may make it may be more dramatic.

We found the log book my dad kept when he built this house, detailing the price for the lot, the kit he built the house from, the nails, and the insulation…Infra Insulation. Googling finds a 1971 reference in Mother Earth News as follows:

Reflective metal foil (copper, aluminum, or steel) costs less than 3 cents a square foot and can be easily installed. One should remember to keep the shiny side out (or up) and leave a ventilated air space inside (or below), and at least 3/4-inch between the foil and the surface it faces. A more expensive but also more highly efficient insulator—aluminum clad, accordion-type material known as Infra Multiple Aluminum Insulation—is manufactured by the Infra Insulation Company, 525 Broadway, N.Y.C. which will send free samples on request.

The only other reference was to a 1954 FTC ruling where the company was ordered to cease-and-desist in overstating the insulating ability of their product. We have never had any reason to complain about the insulation. Our house is always comfy with no cold spots.

So the company was in business as late as 1971. I have no idea on how or where to search further, to find out if the company still exists, if it changed names, anything. Address search comes up blank.

Any ideas on how to search for defunct companies?

Nutmagnet has pretty much nailed it. If the discoloration is happening at the studs, then it’s not the fault of the insulation, because the insulation is usually strictly between the stud bays. The problem is likely that the studs, being solid, tend to be better thermal conductors, so the drywall adjacent gets colder, air condenses, and you get rust stains and general schmutz on the wall. Anecdotally, this is worse if the house has smokers.

If this is only noticeable after 25 years without painting, I don’t think you have to worry about it much. Just put on some stain-killing primer, fix any cracks, and paint again and you’re good for another 25 years or so.