Open Cell Insulation Vapor Barrier

Vapor barrier vapor permeability.

Open cell insulation vapor barrier.

Closed cell foam insulation is non porous with all of the voids closed to each other which makes it difficult for water vapor and air to pass through it. Many of them don t agree that vapor barriers are so necessary even with open cell foam insulation. If there s a roof leak water will pass through the foam and you will quickly be able to find your problem. For example closed cell foam is from class ii and open cell is from class iii.

Open cell needs a class ii vapor retarder old term barrier only in certain climates not all. Spray in insulation and air barrier material. Open cell spray foam is not a moisture vapor barrier and will allow moisture to pass. Structural reinforcement able to deflect water and reject bulk water able to accommodate seasonal shifting.

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. Not every type of insulation needs a vapor barrier. 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. Foam insulation porosity vapor barrier issue.

So if you re considering spraying foam to the roof deck of your new or existing home you want open cell. Open cell spray foam closed cell spray foam. Open cell foam insulation is a porous material that can allow air and moisture to penetrate the insulation. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

R value at 1 3 7. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Ft and it s unaffected by water. Vapor barriers sheets of plastic or kraft paper keep water vapor out of the wall cavity so the insulation stays dry.

Not every wall does. When an area is accessible for maintenance or repair then any foam must have an ignition barrier over the foam or an equivalent material such as properly tested and listed intumescent coating matched to the type and brand of foam or it must be. There are three classes of vapor barriers. Open cell foam is not a vapor barrier so it allows the water from the roof leak to weep through the foam to the space below so it is the better choice for most residential applications.

But if foam is open cell that barrier must be applied.