Fiberglass Attic Insulation R Value

Achieving greater r values in exterior walls.

Fiberglass attic insulation r value.

Depending on where you live it s recommended that attics have a minimum r value of r 30 in warm climates to r 60 in cold climates. It can be located on a card left by the previous installer printed on the attic insulation or you can measure it yourself. If the attic is already insulated you ll want to check the current r value. Insulation level are specified by r value.

The table below shows what levels of insulation are cost effective for different climates and. You can achieve better thermal performance in your attic by adding an additional layer of insulation. Input depth of existing blown in insulation in inches. R value is a measurement of thermal resistance and measures the ability of heat to transfer from one side of an object to another.

First you ll need to determine your r value. In fact the loose fill fiberglass lost 35 to 50 of its resistance to heat flow at temperature differences of 70 f to 76 f. The loss of r value started at a temperature difference of about 32 f. Warmer climates only require an r 38 or higher or about 12 or more.

This calculator is to be used as an estimating tool only. If it s a new building simply reference the energy code map. 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. The higher the r value the better the thermal performance of the insulation.

Recommended home insulation r values. As you can see there s some variation in r value depending on the particular type and brand of products used. The higher the r value the better the thermal performance of the insulation. Houses in a cold climate should have a minimum of r 49 in the attic which is equivalent to approximately 16 of fiberglass insulation.

Click the button to calculate the approximate r value for this job.