Open Cell Spray Foam Attic

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 spray foam attic.

The myth that open cell is more economical is bullshit. 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. 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. Light density open cell spray foam insulation and medium density closed cell spray foam insulation.

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. 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. 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.

Open and closed cell foam insulation use a blowing agent to forms the cells within it. This makes the foam a softer more flexable material. Murmurs and hearsay about open cell spray foam insulation have been gaining traction for a while. Open cell spray foam insulation doesn t store the moisture.

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. It s the wood decking that stores the moisture. Open cell foam weighs 1 2 pound per cubic foot and closed cell weighs 2 lbs per cubic foot.

The role of open cell spray foam. It s just a pathway. This type of spray polyurethane foam can be classified into two different types. 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.

In other words the cells are deliberatly left open. Closed cell foams use enovate also known as 245fa. Open cell foam is full of cells that aren t completely encapsulated.