Required R Value For Attic Insulation

Most homes in the united states are not well insulated.

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. 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. Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces. R 5 shall be added to the required slab edge r values for heated slabs.

Recommended insulation levels for retrofitting existing wood framed buildings. Does your home have enough r value. Add insulation to attic. Achieving greater r values in exterior walls.

The recommended r value for attic floor insulation for this house is r 38. There are many ways to retrofit a home with fiberglass and. Existing 3 4 inches of insulation. This can happen if you add denser insulation on top of lighter insulation in an attic.

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. The homeowner could then check table 1 to find several choices. You will need a higher r value of insulation if you live in the northeast than if you live in southern california. The 2015 irc requires r 49 insulation for ceilings with attic spaces.

Recycled glass or sand that s melted and spun into fibers. 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. Special insulation exceptions related to ceilings with attic spaces ceilings without attic spaces masonry veneer and thermally isolated sunrooms are set forth in iecc. Pa302 1 ceilings with attic spaces n1102 2 1 r402 2 1.

Your home s age if your home is more than 10 year old you likely need more 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. However there is an exception. Insulation requirements for slab on grade floors is further specified in iecc section 402 2 8.

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. Where you live different climates require different insulation r values.