Desired R Value For Attic

Calculate the square footage of the attic you re insulating.

Desired r value for attic.

You can compensate for this stacking effect and achieve the desired total r value by adding about one extra inch of insulation if the old insulation is fiber glass or about 1 2 inch if the old insulation is rock wool or cellulose. Insulation level are specified by r value. Recommended home insulation r values. You may choose to do it yourself or hire a contractor.

You will need a higher r value of insulation if you live in the northeast than if you live in southern california. The next step is to visit with an insulation specialist to determine the kind and amount of insulation that will be needed to bring your attic space up to the desired r value. The higher the r value the better the thermal performance of the insulation. Be sure to carefully follow the installation instructions to get the desired insulation r value.

For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3. Measure the length and width of the attic then multiply those numbers to get the total square footage. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. How to calculate existing r value in an attic.

An r value is a measure of a given material s. This effect is most important if the new insulation is more dense than the old insulation. Subtract that amount from the desired r value for your home s zone to. Where you live different climates require different insulation r values.

Instructions on the product where current r value is listed will guide you through estimating the number of packages to buy based on the number of square feet you re insulating and the desired r value. This zone s recommended r value for an uninsulated attic is r30 to r60. Once determined subtract the current r value from your desired r value to get the r value you need to add. If the 1000 square foot attic previously had 9 inches r 24 of insulation and an r value of 60 is desired an additional 13 25 inches r36 of insulation would be required.

Per bag 18 4 bags an additional 19 bags of insulation would therefore achieve an r value of 60. There are many ways to retrofit a home with fiberglass and. Determining your attic insulation needs. Your home s age if your home is more than 10 year old you likely need more insulation.

Of inches to determine your existing r value.