Will A Roof Leak Travel With Open Or Closed Foam

Closed cell spray foam insulation has a tendency to fill voids and gaps because it doesn t expand as much as open cell insulation.

Will a roof leak travel with open or closed foam.

I have taken apart existing leaking roofs all over the place open cell closed cell sips compact etc. Chemical manufacturer s claim if a roof leaks water will migrate through the foam structure therefore not trapping the water. Open cell foam is just that open cell. Let s not confuse open cell vs closed cell foam.

Moisture barrier open cell spray foam is not a moisture vapor barrier and will allow moisture to pass. A sealed and insulated roof deck can t dry inward to the attic if the roofing happens to let water. Closed celled foams will perform better in terms of deflecting water away from interior elements but may allow leaks to go undetected longer. If there s a roof leak water will pass through the foam and you will quickly be able to find your problem.

As with all construction products installation is critical to the performance of the product. Common sense tell s me if this is valid marketing then what stops water vapor from moving through the foam under pressure. Open cell spray foam not only insulates to improve temperature consistency but it also seals cracks and crevices that allow air to leak into and out of your home. Open cell foams will tend to leak closer to the point of entry making leaks easier to identify and locate.

Note that not all open cell spray foam insulations have the exact same physical properties as some are able to absorb a significant amount of water which could aggravate moisture conditions in an attic. With the mock ups and the field experience i have not noticed any difference between open cell and closed cell in terms of detectability and damage with respect to roof leaks. Open cell foams will tend to leak closer to the point of water entry making leaks easier to identify and locate. That s an important consideration because if there s a leak in the roofing or the ridge cap moisture could get trapped between the roof and the insulation.

This can be especially helpful in attic encapsulation where high temperatures can force hot air through gaps around joints air ducts and light fixtures.