Required R Value For Attic Insulation

Insulation requirements for slab on grade floors is further specified in iecc section 402 2 8.

Required r value for attic insulation.

Add insulation to attic. Special insulation exceptions related to ceilings with attic spaces ceilings without attic spaces masonry veneer and thermally isolated sunrooms are set forth in iecc. 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. This can happen if you add denser insulation on top of lighter insulation in an attic.

R 5 shall be added to the required slab edge r values for heated slabs. 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. 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. Existing 3 4 inches of insulation.

Does your home have enough r value. However there is an exception. Achieving greater r values in exterior walls. The 2015 irc requires r 49 insulation for ceilings with attic spaces.

You can achieve better thermal performance in your attic by adding an additional layer of insulation. Recommended insulation levels for retrofitting existing wood framed buildings. The recommended r value for attic floor insulation for this house is r 38. 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.

You will need a higher r value of insulation if you live in the northeast than if you live in southern california. Recycled glass or sand that s melted and spun into fibers. Your home s age if your home is more than 10 year old you likely need more 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.

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. There are many ways to retrofit a home with fiberglass and. However there is an exception. Where you live different climates require different insulation r values.

The higher the r value the better the thermal performance of the insulation. Pa302 1 ceilings with attic spaces n1102 2 1 r402 2 1.