Metal Foil Attic Insulation Blankets

I ran into the metal foil insulation blankets in an attic today. This is a 50’s home that was recently insulated with this material on the rafters and blown-in fiberglass on the floor.
I’ve seen this twice in a month. I can go years between seeing it. Years ago, when I researched it, I found conflicting information and opinions.
When on the floor of an attic, there were concerns about trapping moisture vapor between the foil blankets and house ceiling. When attached to the underside of the roof decking and rafters, there were stories of over-heating the shingles and causing pre-mature aging of composition shingles.
Jus’ wonderin’ if any of you have more experience with this and know more than I do and what you think about it.

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I have only seen it laying on top of the insulation. Every time it was torn up so trapping humidity was not really a concern. More than likely, the cable guy destroyed it.


Looks like radiant barrier.

I seen it fairly often, but don’t pay any attention to it.

If you look at it, it is perforated so vapor could travel through it. If I’m understanding you above the radiant barrier is a fiberglass insulation and then the roof deck directly of above. My thinking is, and it probably depends a lot on your climate, water vapor can go through the perforations and somewhere in that insulation it is going to hit the dewpoint and entrap moisture especially if there is not ventilation throughout the whole area (above) where this is applied.

In my opinion I would not be using a second layer of fiberglass/thermal insulation above this radiant barrier.
I am a big advocate of a radiant barrier being installed at the roof decking however as it will drop your attic temperatures significantly and actually keep your attic temperatures much warmer in the winter. The best radiant barrier in my opinion is that is applied at the factory directly to the OSB or plywood. such as the home I just inspected today. This is the bottom of the roof decking and notice that it is perforated so that any moisture from a roof leak can escape instead of staying wet and rotting the deck.


A good salesman in area.
Or another government energy program.

Keep the faith,
Indianapolis, IN

Yes, this is a Radiant Barrier and most (even the D.O.Energy) will say (when property installed) can reduce your attic temps by 90%+.

It’s perforated so it can breathe, it’s said to have a R-Factor of 187 or compared to 7’ (feet) of traditional fiberglass insulation.

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Yes! But so rarely properly installed, and so often sold by salespeople also engaged in the squamata extractive bottling business.

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I must say, that was pretty creative… are you saying you wouldn’t want the extra 35% energy savings enabling you to spend that money on those new golf clubs or dinner out with the wife, by Our Math here that’s almost $9,000 (after install and commission costs:) over a 15yr period.
:slight_smile: Cheif Bottle Salesman…

So, none of you have heard or seen issues with cooked composition shingles?
Larry’s photo doesn’t look like a concern for overheating. TechShield is the decking and will reflect heat back through the shingles like sprayed foam does. BTW, I’ve never seen this material. Was the attic floor insulated?
Jeffrey’s example has photos of two materials and installations, both are different than what I saw. When I looked into this years ago, I saw some observations that the blanket-type barrier material that had an air gap between the underside of the decking and the barrier was trapping heat and cooking the composition shingles. The barrier was falling down in the attic of the other home I saw a few weeks ago, so ventilation under the roof deck was not a problem. BTW, another complaint that I saw about this stuff, was that it acted like a lightning rod.
And how does the cost of installing spray foam vs. these radiant barrier systems compare?
On the house I inspected yesterday, that radiant barrier looked like a labor-intensive installation. There was a sealed zippered cover over the attic access!
In the Denver metro, inadequate attic ventilation in our over twenty years old homes, is arguably, the number one enemy of our shingled roofs with hail being a close second.