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Recommended Levels of Insulation

Insulation level are specified by R-Value. R-Value is a measure of insulation’s ability to resist heat traveling through it. The higher the R-Value the better the thermal performance of the insulation. The table below shows what levels of insulation are cost-effective for different climates and locations in the home.

Recommended insulation levels for retrofitting existing wood-framed buildings

US map showing recommended insulation levels for retrofitting existing wood-framed buildings

Zone Add Insulation to Attic Floor
Uninsulated Attic Existing 3–4 Inches of Insulation
1 R30 to R49 R25 to R30 R13
2 R30 to R60 R25 to R38 R13 to R19
3 R30 to R60 R25 to R38 R19 to R25
4 R38 to R60 R38 R25 to R30
5 to 8 R49 to R60 R38 to R49 R25 to R30

Wall Insulation: Whenever exterior siding is removed on an

Uninsulated wood-frame wall:

  • Drill holes in the sheathing and blow insulation into the empty wall cavity before installing the new siding, and
  • Zones 3–4: Add R5 insulative wall sheathing beneath the new siding
  • Zones 5–8: Add R5 to R6 insulative wall sheathing beneath the new siding.

Insulated wood-frame wall:

  • For Zones 4 to 8: Add R5 insulative sheathing before installing the new siding.