Roof Insulation R Value Thickness

Recommended home insulation r values.

Roof insulation r value thickness.

Zone 6 requires an r 30 minimum which is 5 2 thick. Insulation level are specified by r value. Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces. To achieve a construction r value of 3 3 using the branz house insulation guide see page 35 rafters and dwangs an insulating material of r3 4 will be required.

Add the results for all the materials together to get the total r value for the roof assembly. 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. This exception will allow the minimum thickness to be 4 2 at the low point or 5 2 4 away from the drain on a per foot tapered system. Hunter panels roofing tech topic r105.

Recognized by the iecc. Fm approved subject to the conditions of approval as a roof insulation when installed as shown in the current edition of the factory mutual research approvals guide. Firestone isogard polyiso insulation goes even further and was the first product on the market to meet both astm c1289 required and recommended thermal performance values. To calculate the total r value of a roof assembly find the total thickness in inches of each type of insulating material within the system.

There is an exception provided that allows the minimum thickness to be up to 1 less than the prescriptive r value at per foot slope as long as the system r value meets or exceeds that prescriptive r value. The table below shows what levels of insulation are cost effective for different climates and. 2 layers of 1 40 iso 16 0 r value vs 2 layers of 1 60 iso 18 2 r value isogard hd board 2 5 r value vs gypsum 28 total r value 18 5 vs total r value 18 48 utilizing the firestone isogard hd cover board helps reduce the thickness of the initial layers of insulation and thereby reduces the costs of the project. Excellent lttr value compared to any other fm class 1 rated products of equivalent thickness.

Note from this chart that the ideal r value differs for each part of your home. Firestone iso 95 gl polyiso insulation has a higher r value than other insulation products while also outperforming competitive polyiso at low temperature. The higher the r value the better the thermal performance of the insulation. To compare different insulation products researchers have to create the exact same conditions and then measure how well the insulation performs.

R value is a measure of insulation s ability to resist heat traveling through it. But what does that mean and how do researchers determine r value. Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value.