Fiberglass Attic Insulation R Value

The higher the r value the better the thermal performance of the insulation.

Fiberglass attic insulation r value.

If the attic is already insulated you ll want to check the current r value. If it s a new building simply reference the energy code map. Click the button to calculate the approximate r value for this job. 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. 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. R value is a measure of insulation s ability to resist heat traveling through it. You can achieve better thermal performance in your attic by adding an additional layer of insulation.

R value is a measurement of thermal resistance and measures the ability of heat to transfer from one side of an object to another. Recommended home insulation r values. This calculator is to be used as an estimating tool only. Achieving greater r values in exterior walls.

It can be located on a card left by the previous installer printed on the attic insulation or you can measure it yourself. 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. Input depth of existing blown in insulation in inches. 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.

Warmer climates only require an r 38 or higher or about 12 or more. Insulation level are specified by r value. 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 loose fill fiberglass showed a significant reduction in r value as the attic got colder and the temperature difference got larger.