Rigid Insulation R Value Table

Please note that the r values for roof membranes shingles tiles air films and roof deck materials might or might not be permitted by your local code to be included when total roof assembly r value is being calculated for the purpose of.

Rigid insulation r value table.

R values vary depending on many factors including the mean temperature at which the test is conducted and the age of the sample at the time of testing. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. Notes to the table above. Foam board insulation types.

It provides r values that range from 3 6 to 4 2 per inch. For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3. I ve written several posts about how to insulation basement walls in which i promote the use of foam board insulation as the first line of defense against moisture and mold. As a benchmark one inch of solid wood has an r value of 1.

Choose this option for areas that need a good amount of strength and water resistance. The formula for r value is. In service r values of 5 0 per inch thickness in predominant heating climate conditions and 5 6 per inch thickness in predom inant cooling climate conditions. For example two inches of extruded polystyrene with an r value of 11 has an rsi of 1 93721.

To convert the r value of a specific thickness of a material to rsi divide the r value by 5 67826. 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. There are three basic foam insulation board products on the. That formula is in imperial units.

This material offers the highest r values about r 6 to 6 5. Rosato asbestos insulation is the most authoritative source on asbestos properties and gives data for the thermal conductivity of asbestos in different forms and with varying temperatures for magnesia asbestos insulation at mean temperatures ranging from 100 f to 400 f the k value thermal. Because rigid foam plastic insulation products are not all aged in accordance with the same standards it is useful to publish comparison r value data. To convert rsi to r value multiply the rsi by 5 67826.

Btu hr x ft 2 x f in this formula btu stands for british thermal units hr stands for time lapse in hours ft 2 stands for the exposed area of the sample in square feet and f stands for change in temperature by degrees fahrenheit. The common denominator among varieties of insulation is the r value. Notes on the r value k values of different forms of asbestos. It provides about r 5 per inch.

For instance if you have a material with an r value of 12 attached to another material with an r value of 3 then both materials combined have an r value of 15. In simple terms r values measure the effectiveness of insulation and a higher number represents more effective insulation.