Thread: Thermal barrier installed wrong? See photos..What say ye?

We all have seen different types of aftermarket "Thermal" protection for attics, from silver spray paint to thermal decking, etc. This one in today's inspection utilized heavy foil paper installed and lying on top of the existing and original loose fill fiberglass insulation. All the loose fill insulation in the attic was covered by this foil. (The roof sheathing/decking was just regular wood OSB plywood). As I was looking at this today it appears to me maybe it installed wrong? ( I am thinking vapor barrier here). Assuming that you accept that a lot of mositure from inside the house makes it way to the attic and attic insulation, the mositure from the house would be trapped inside the insulation, because the attic insulation now has a foil paper covering it. From my view, this would prevent the attic loose fill insulation from "breathing". Seems this foil would hold household moisture inside the insulation rather than allowing it to escape.... What say ye insulation vapor barrier experts? I have included photos however they are not great. Look close. There is also foil covering the fiberglass wall batt insulation. I have checked a few websites and they do warn of a moisture trap in some cases.

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Some of this stuff is pin-pricked to allow vapor to pass through. Try and feel for the bumps and shine your light through it.
You definitely do not want a vapor barrier in that position. According to studies I have read about, attic floor vapor barriers are effective but rapidly loose there radiant barrier effectiveness as the inevitable dust layer covers the product.

The radiant barrier approach that we see in these pictures is fairly typical as long as it is not intended to be a vapor barrier. I have seen new construction with the foil barrier actually placed on the underside of the deck. The purpose is to act like a foil blanket similar to the ones used in emergency camp kits.

Vapor barrier location depends on the location. In Utah where the ambient air is dry the moisture barrier is placed on the inside of the thermal barrier. In Florida it is placed on the outside of the thermal barrier.

My 2 cents. HTH.

Looks pretty obvious there are air holes and appears sufficient to not worry about, if it was a home old enough in an area that has been through a few good heat/cold seasons you can lift an area, if it is causing any problem you will certainly see moisture evidence whether it be on the wood or elsewhere..

Foil radiant barriers are typically snake oil. They work best in poorly insulated homes. But if the home is poorly insulated reflective barriers are not the place to start. After a home has been well insulated you will find that it is no longer cost effective to install a radiant barrier.

In the picture the problem you have is that you dont know what is under the foil/reflective barrier. The perforated barrier might be fine in a well sealed attic. In an attic with air leaks I would be concerned about the air leaks bringing up moisture and it condensing.