Roof Insulation R Value Thickness

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.

Roof insulation r value thickness.

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. Excellent lttr value compared to any other fm class 1 rated products of equivalent thickness. Firestone iso 95 gl polyiso insulation has a higher r value than other insulation products while also outperforming competitive polyiso at low temperature. Note from this chart that the ideal r value differs for each part of your home.

Insulation level are specified by r value. Recognized by the iecc. But what does that mean and how do researchers determine r value. Hunter panels roofing tech topic r105.

Add the results for all the materials together to get the total r value for the roof assembly. 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. Recommended home insulation r values. Zone 6 requires an r 30 minimum which is 5 2 thick.

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. To compare different insulation products researchers have to create the exact same conditions and then measure how well the insulation performs. At one inch thickness enerfoil tm achieves a 6 2 r value or a 1 08 rsi. 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.

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. 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. 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. For each different material multiply the thickness by the standard r value per inch for that material.

The table below shows what levels of insulation are cost effective for different climates and. None of the available insulating materials will fit within the depth of a 90 mm rafter but by selecting a 140 mm deep rafter it is possible to fit a wider choice of products including r values that exceed the minimum see figure 2. The higher the r value the better the thermal performance of the insulation.