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.

Finished attic insulation r value.

Add insulation to attic. However there is an exception. The higher the r value the greater the insulation performance. R value measures how well certain building insulation materials can resist heat.

Recycled glass or sand that s melted and spun into fibers. Rigid foam sheeting has an r value ranging from r 5 to r 10 per inch of thickness. Existing 3 4 inches of insulation. In general an attic s r value should be between r 30 and r 49.

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. The homeowner could then check table 1 to find several choices. 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. The 2015 irc requires r 49 insulation for ceilings with attic spaces.

Of combined fiberglass and foam insulation. Know exactly how much you need with our project calculators. Zone the area under a. For homes in the seattle washington area we ve already established that the correct insulation r value climate zone is 4.

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. Where you live different climates require different insulation r values. Install air chutes before installing insulation why your roof needs air chutes. Pa302 1 ceilings with attic spaces n1102 2 1 r402 2 1.

The recommended r value for attic floor insulation for this house is r 38. Let s say the insulation you ve selected has an r value of three per inch and. When determining how much insulation you need don t guesstimate calculate. In addition to climate r value also depends on the age of your home.

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. This means you can have a combined r value ranging from r 23 to r 31 with only 5 1 2 in. Your home s age if your home is more than 10 year old you likely need more insulation. You will need a higher r value of insulation if you live in the northeast than if you live in southern california.

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. Recommended insulation levels for retrofitting existing wood framed buildings.