Bubbles on facing side of Rigid Insulation

[Greg Subick]

saw this in a home yesterday that have not seen before. Large bubbles on the facing side of rigid insulation in three different attics. Ventilation in all three was very good-temperature outside was 77, temps in attic averaged about 86. What causes this? I cut a small one open and didn't see anything alarming beneath the bubble-no damage to insulation or anything. Cause for concern?



30819

[Scott Patterson]

I have found that several times and when I contacted a manufacturer they say it is caused by moisture vapor. The moisture wicks it's way through the cladding and is stopped by the vinyl coating that is on the attic side of the insulation board. Causes no problems but can be a red flag that the cladding might have a problem.

The same thing can happen inside a home if dark pigmented paint is applied to a wall and it is not allowed to dry naturally between additional coats of paint( do not use fans or torpedo type heaters to help dry). The surface skims over and fees dry but the paint is wet underneath, you apply more coats and you will get water blisters.