Open Cell Spray Foam Attic

A spray insulation is referred to open cell or closed cell because of the difference between the small bubbles cells that make up the foam.

Open cell spray foam attic.

It has a relatively high vapor permeance 3 perms allowing water vapor to migrate to the roof decking at night and back into the attic air in the daytime. The spray foam insulation or spray polyurethane foam spf is a popular alternative to traditional building insulation such as fiberglass. Open cell foams use water as a blowing agent. Not long ago someone even told me that in florida roofing companies won t let their workers go up on roofs with open cell spray foam because the roofs are so spongy the guys fall right through.

Light density open cell spray foam insulation and medium density closed cell spray foam insulation. It s the wood decking that stores the moisture. It s just a pathway. There is 300 difference there but the cost they give you is about a third difference and open cell foam at 12 inches will not give you the performance of 2 inches of closed.

This spray foam is applied as a low or high pressure two component polyurethane spray foam that can be applied onto walls in unvented attics to ducts and ceilings and in vented attics and. Open cell spray foam insulation doesn t store the moisture. The role of open cell spray foam. Open cell foam weighs 1 2 pound per cubic foot and closed cell weighs 2 lbs per cubic foot.

In other words the cells are deliberatly left open. An open cell foam low density spray polyurethane is a spray applied to provide continuous insulation and an air sealing barrier. Open cell spray foam can also be used to create an unvented attic in cold climate zones provided code requirements for a vapor retarder are followed. Some spray foam manufactures have tested primer coating products that result in the formulation of a class ii vapor retarder directly on the surface of the open cell spray foam.

This makes the foam a softer more flexable material. The superior air sealing performance of spray foam insulation both open and closed cell results in moisture movement by vapor diffusion increasing in importance. Open cell foam is full of cells that aren t completely encapsulated. It rots roofs people have told me.

Building code vapor retarder requirements for unvented attic construction have been in place since the 2009 irc and have resulted in thousands of successful assemblies that contain. Open and closed cell foam insulation use a blowing agent to forms the cells within it. This type of spray polyurethane foam can be classified into two different types.