Fiberglass Attic Insulation R Value

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.

Fiberglass attic insulation r value.

Insulation level are specified by r value. Click the button to calculate the approximate r value for this job. The loose fill fiberglass showed a significant reduction in r value as the attic got colder and the temperature difference got larger. 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. As a benchmark one inch of solid wood has an r value of 1. As you can see there s some variation in r value depending on the particular type and brand of products used. The loss of r value started at a temperature difference of about 32 f.

It can be located on a card left by the previous installer printed on the attic insulation or you can measure it yourself. Houses in a cold climate should have a minimum of r 49 in the attic which is equivalent to approximately 16 of fiberglass insulation. The higher the r value the better the thermal performance of the insulation. The table below shows what levels of insulation are cost effective for different climates and.

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. First you ll need to determine your r value. Warmer climates only require an r 38 or higher or about 12 or more. R value is a measure of insulation s ability to resist heat traveling through it.

If it s a new building simply reference the energy code map. If the attic is already insulated you ll want to check the current 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. Recommended home insulation r values.

Achieving greater r values in exterior walls.