Finished Attic Insulation R Value

Of combined fiberglass and foam insulation.

Finished attic insulation r value.

But the roof is a major pathway to heat loss and gain so it s worth shelling out the extra bucks for spray foam. This means you can have a combined r value ranging from r 23 to r 31 with only 5 1 2 in. Recommended insulation levels for retrofitting existing wood framed buildings. However there is an exception.

In general an attic s r value should be between r 30 and r 49. Your home s age if your home is more than 10 year old you likely need more insulation. If the existing attic floor insulation has an r 11 insulation value then an additional r 27 would be needed to bring the attic floor insulation up to the level recommended for that house. The recommended r value for attic floor insulation for this house is r 38.

R 38 shall be deemed to satisfy the requirement for r 49 wherever the full height of uncompressed r 38 insulation extends over the wall top plate at the eaves. If you look at the chart above you can see that the attic should achieve an r value between r 38 and r 60 depending on the current insulation levels. Install air chutes before installing insulation why your roof needs air chutes. In particularly cold climates you might go up to r 60.

Add insulation to attic. Pa302 1 ceilings with attic spaces n1102 2 1 r402 2 1. In addition to climate r value also depends on the age of your home. It costs two to three times more than fiberglass batt insulation.

Know exactly how much you need with our project calculators. Existing 3 4 inches of insulation. There are many ways to retrofit a home with fiberglass and. Rigid foam sheeting has an r value ranging from r 5 to r 10 per inch of thickness.

Where you live different climates require different insulation r values. The 2015 irc requires r 49 insulation for ceilings with attic spaces. The homeowner could then check table 1 to find several choices. For homes in the seattle washington area we ve already established that the correct insulation r value climate zone is 4.

When determining how much insulation you need don t guesstimate calculate. The higher the r value the greater the insulation performance. Lighter in weight than cellulose or mineral wool but it settles more than those materials so you ve got to put in a thicker layer to get the protection you need. It forms a much tighter air barrier and you ll get the same r value with fewer inches of the stuff so you ll have extra room overhead.

Zone the area under a. Let s say the insulation you ve selected has an r value of three per inch and.