Open Cell Insulation Vapor Barrier

If there s a roof leak water will pass through the foam and you will quickly be able to find your problem.

Open cell insulation vapor barrier.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. 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. R value at 1 3 7.

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. Many of them don t agree that vapor barriers are so necessary even with open cell foam insulation. But if it does the barrier should face inside in northern heating climates and outside in humid southern climates. 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. Scientists still discuss if those methods are efficient. Vapor barriers sheets of plastic or kraft paper keep water vapor out of the wall cavity so the insulation stays dry. Open cell spray foam closed cell spray foam.

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. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. 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. Open cell spray foam is not a moisture vapor barrier and will allow moisture to pass.

Foam insulation porosity vapor barrier issue. Vapor barrier vapor permeability. Ft and it s unaffected by water. Not every type of insulation needs a vapor barrier.

Structural reinforcement able to deflect water and reject bulk water able to accommodate seasonal shifting. Open cell foam insulation is a porous material that can allow air and moisture to penetrate the insulation. Not every wall does. Spray in insulation and air barrier material.

So if you re considering spraying foam to the roof deck of your new or existing home you want open cell.