Polyisocyanurate Insulation R Value Per Inch

The increase in thermal resistance for thicker products is due to the reduced contribution of more thermally conductive elements such as the facer and the denser cell.

Polyisocyanurate insulation r value per inch.

Along with knowing the r value of a particular insulation it is also important to calculate the r value of a total system. 1 2014 industry issue update polyiso s r value provided an overview of the theory of foam aging. In comparison an inch of blown fiberglass insulation has an r value of 3 1 3 4 and an inch of blown cellulose in an attic has an r value of 3 2 3 7. This in service r value was intended to account for polyisocyanurate insulation s r value losses over time and provides a more realistic design r value for polyisocyanurate insulation during a roof sys tem s entire design life.

Polyiso is typically used with a foil facing and it has an r value of 7 0 to 8 0 per inch of thickness. For example a two inch polyiso product has more than twice the insulating value than a one inch product. As a benchmark one inch of solid wood has an r value of 1. Keep in mind that polyiso s r value increases with thickness.

Polyiso is unique in that the r value increases with the thickness of the foam so three inches of polyiso has a higher r value per inch than two inches. Polyiso offers a r 6 5 and the highest r value per inch when compared to other insulation. And nrca s r value recommendations associated with the use of polyisocyanurate insulation used in roof systems. The r value test method and the long term thermal resistance lttr methodol ogy.

Insulation is the product found to provide the greatest investment return and offer the most carbon abatement. Polyiso has a high r value per inch compared to other insulation products. Based on consensus standards in both the united states and canada long term thermal resistance lttr is a scientifically supported method to calculate the 15 year time weighted average r value of roof insulation. Polyiso which forbes considers a green insulation offers the highest r value in its class with a 20 70 greater r value per inch than any other rigid foam plastic insulation.