Spray On Moisture Barrier Foam Insulation

Closed cell spray foam limitations.

Spray on moisture barrier foam insulation.

If the basement in question has a problem with external liquid water migration this issue can not be solved with spray foam. Moisture barriers should be installed on the cold side of the insulation. Spray foam systems provide the highest level of thermal insulation and provides a monolithic fully sealed air and moisture barrier. But if foam is open cell that barrier must be applied.

Ccspf is a great air and vapor barrier but it is not effective at sealing liquid water leaks. If a home has spray foam insulation in an attic or crawl space the building code requires using materials or assemblies that offer some fire resistance but not as much as is required for a thermal barrier. There are three classes of vapor barriers. The sources and causes of the water need to be corrected before the spray foam is installed.

Years ago approximately 2 1 2 inches of 2 lb. If there s a roof leak water will pass through the foam and you will quickly be able to find your problem. They are combined with flashing and other materials to ensure that there is a shingled assembly to direct liquid water. Vapor barrier unlike other insulation systems closed cell spray foam will create a vapor barrier if sprayed at a certain thickness.

Open cell spray foam is not a moisture vapor barrier and will allow moisture to pass. Since spray foam is an air barrier and insulation it stops the air flow and moisture movement. Many of them don t agree that vapor barriers are so necessary even with open cell foam insulation. One manufacturer demilec says its heatlok high lift spray foam has an even higher r value r 7 5 per in closed cell foam is much denser about 2 lb.

Moisture barriers are specifically designed not to be a vapor barrier as the minimum water vapor permeance for a water resistive barrier is 300 perms. The chemicals being sprayed these days only require one inch of foam. So if you re considering spraying foam to the roof deck of your new or existing home you want open cell. For some manufacturers the foam is required to be at least 2 5 thick to qualify as a vapor barrier.

Of note the thickness required is product specific. Closed cell spray foam can be a vapor barrier after it is installed at least 1 5 thick. Foam was required before qualifying as a vapor barrier. Spray foam is used as thermal barrier air barrier moisture resistant and in some cases as sound proofing product.

Closed cell foam has a much higher r value than open cell foam about r 6 5 per inch and it s a vapor barrier as well as an air barrier. Ft and it s unaffected by water. For example closed cell foam is from class ii and open cell is from class iii. Its spray applied installation process speeds construction and reduces labor costs substantially estimated up to 1 square foot.