R Value Of Polyurethane Foam

Rsi r value système international is the metric equivalent.

R value of polyurethane foam. In the case of materials it is often expressed in terms of r value. 1 8 2 pound polyurethane foam has the highest r value of readily available spray foam insulation used in homes and buildings. Additional r value for a masonry wall constructed using these materials needs to add the insulating value of additional wall components typically included such as 1 solid foam polyisocyanurate r 8 extruded polystyrene r 5 expanded polystyrene r 4 or 1 of perlite r 2 7 and for an exterior air film winter no wind r 0 17 an interior. The r value is the building industry term for thermal resistance per unit area it is sometimes denoted rsi value if the si metric units are used.

Polyurethane and polyisocyanurate are both closed cell foams. In 1970 the popular number for the r value of one inch of urethane foam was 9 09 per inch. A typical 2 4 stud filled with open cell spray foam will have an r value between 10 5 and 14. To convert rsi to r value multiply the rsi by 5 67826.

This is very important in situations where your code requires an r 21 for the wall but you only have a 2 4 stud because closed cell spray foam is the only way you would achieve the required r value to meet code. R value is used in the united states. An r value tells you how well a type of insulation can keep heat from leaving or entering your home. An r value can be given for a material e g.

However fiberglass generally does not provide as tight a seal as a foam product would since it is unable to achieve as tight of a seal. This was much less than the r 16 claimed by fiberglass insulators. Using this value we were putting an r of 1 25 x 9 09 11 36 in the walls. Cost polyiso is the most expensive of the foam board insulation products however it s the highest r value.

The higher the density of the foam the higher the r value per inch. Typically a higher insulation r rating means better climate control and better energy efficiency for your home. Low density foams are referred to as open cell spf while higher density foams are referred to as closed cell foam. For example two inches of extruded polystyrene with an r value of 11 has an rsi of 1.

They contain low conductivity gases in the cells usually one of the hcfc or cfc gases. Insulation r values vary based on the type thickness and density of the insulation material. That means if you used foam it green closed cell which is r 7 per inch it s r value for a 3 5 deep wall cavity would be r 24 5. Energy studies show that fiberglass insulation can loose up to 8 of its r value before the contractor even installs it.

Compared to how traditional insulation performs over time commercial spray foam insulation has a far superior r value. For polyethylene foam or for an assembly of materials e g. Spray polyurethane foam comes in a range of densities and cell structure. To convert the r value of a specific thickness of a material to rsi divide the r value by 5 67826.