Required R Value For Attic Insulation

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.

Required r value for attic insulation.

Where you live different climates require different insulation r values. Special insulation exceptions related to ceilings with attic spaces ceilings without attic spaces masonry veneer and thermally isolated sunrooms are set forth in iecc. The higher the r value the better the thermal performance of the insulation. With an r value of 4 0 to 5 1 per inch depending on the manufacturer pre expanded injection foam provides a higher r value than fiberglass or cellulose and it seals the building from air leakage at the same time.

Most homes in the united states are not well insulated. However there is an exception. Add insulation to attic. Existing 3 4 inches of 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. Pa302 1 ceilings with attic spaces n1102 2 1 r402 2 1. The homeowner could then check table 1 to find several choices. It also happens if you place batts rated for one thickness into a thinner cavity such as placing r 19 insulation rated for 6 1 4 inches into a 5 1 2 inch wall cavity.

You can achieve better thermal performance in your attic by adding an additional layer of insulation. 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. Your home s age if your home is more than 10 year old you likely need more insulation. Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value.

Insulation requirements for slab on grade floors is further specified in iecc section 402 2 8. You will need a higher r value of insulation if you live in the northeast than if you live in southern california. Recommended insulation levels for retrofitting existing wood framed buildings. This can happen if you add denser insulation on top of lighter insulation in an attic.

There are many ways to retrofit a home with fiberglass and. However there is an exception. Does your home have enough r value. Achieving greater r values in exterior walls.

The recommended r value for attic floor insulation for this house is r 38. The 2015 irc requires r 49 insulation for ceilings with attic spaces.