Fiberglass Attic Insulation R Value

If the attic is already insulated you ll want to check the current r value.

Fiberglass attic insulation r value.

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. Click the button to calculate the approximate r value for this job. R value is a measure of insulation s ability to resist heat traveling through it.

The loose fill fiberglass showed a significant reduction in r value as the attic got colder and the temperature difference got larger. Insulation level are specified by r value. Recommended home insulation r values. First you ll need to determine your r value.

Input depth of existing blown in insulation in inches. The table below shows what levels of insulation are cost effective for different climates and. 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. R value is a measurement of thermal resistance and measures the ability of heat to transfer from one side of an object to another.

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. You can achieve better thermal performance in your attic by adding an additional layer of insulation. It can be located on a card left by the previous installer printed on the attic insulation or you can measure it yourself. If it s a new building simply reference the energy code map.

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

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.