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How much does attic insulation save?
It depends most on how much insulation is up there now. Bringing an attic with almost none up to R-49 saves about 33% of what a home spends on heating and cooling; topping up one that already has a moderate layer saves about 5%.
Short answer: with less than about 4 inches of insulation, air sealing and insulating the attic pays back in 7–26 years for the example home, depending on the state. With 8 to 11 inches already there, it takes at least 49 years.
How much is up there now
Look in the attic and measure the insulation's depth between the joists. The Upgrade Ladder asks for it in four bands: none or very little (0–3 inches), some (4–7), moderate (8–11) and deep (12 or more). A deep attic is already done, so the upgrade doesn't appear on the ladder; "Not sure" is counted as some.
What decides the savings
The share of heating and cooling it removes. The ladder uses the Illinois manual's heat-transfer method (IL-TRM v14.0, section 5.6.5) on a documented reference home: about 33% of heating and cooling from a bare attic, 16% from a partly insulated one and 5% from a moderately insulated one, each brought up to R-49.
What you spend on heating and cooling. The same share is worth more in a home that spends more on heating and cooling. The ladder measures that from your own bills where it can (How much of your energy goes to heating and cooling).
Air sealing first. Seal the ceiling's leaks (top plates, wiring holes, the attic hatch) before adding insulation: insulation laid over open leaks does much less.
What it costs
The ladder starts from $1,800–$4,500 for blown-in insulation on a typical attic and adjusts it to your area's costs with RSMeans city cost indices. A bigger attic costs more than that.
By state
The table runs one house: the example home from the example ladder, a 1960s single-family home with gas heat and central air that spends $2,600 a year on energy ($1,900 of electricity and $700 of gas). Each row moves that same house, with the same bills, to another state. What changes from row to row is how much of a typical home's energy spending goes to heating and cooling in that state (EIA's household energy survey) and the state's construction costs. Your own bills will move the figures, up or down.
Air-sealing and insulating the attic: yearly savings and simple payback for the example home, in each of the tool's state choices, by the insulation already there
| State | None or very little (0–3 in) | Some (4–7 in) | Moderate (8–11 in) |
|---|---|---|---|
| Alabama | $318/yr 8 years | $154/yr 17 years | $48/yr 55 years |
| Alaska | $167/yr 22 years | $81/yr 45 years | $25/yr 144 years |
| Arizona | $357/yr 8 years | $173/yr 16 years | $54/yr 50 years |
| Arkansas | $326/yr 8 years | $158/yr 16 years | $49/yr 51 years |
| California — Coast (SF/LA/San Diego) | $220/yr 17 years | $107/yr 35 years | $33/yr 111 years |
| California — Inland valleys / LA basin | $238/yr 16 years | $115/yr 32 years | $36/yr 103 years |
| California — Central Valley & desert | $244/yr 15 years | $118/yr 31 years | $37/yr 100 years |
| California — Mountains / high desert | $271/yr 14 years | $131/yr 28 years | $41/yr 91 years |
| Colorado | $256/yr 11 years | $124/yr 22 years | $39/yr 71 years |
| Connecticut | $267/yr 13 years | $130/yr 27 years | $41/yr 85 years |
| Delaware | $278/yr 12 years | $135/yr 25 years | $42/yr 79 years |
| District of Columbia | $293/yr 10 years | $142/yr 21 years | $44/yr 67 years |
| Florida | $313/yr 8 years | $152/yr 17 years | $47/yr 55 years |
| Georgia | $312/yr 9 years | $151/yr 18 years | $47/yr 57 years |
| Hawaii | $142/yr 26 years | $69/yr 54 years | $22/yr 174 years |
| Idaho | $230/yr 13 years | $112/yr 26 years | $35/yr 83 years |
| Illinois | $302/yr 11 years | $146/yr 24 years | $46/yr 75 years |
| Indiana | $290/yr 10 years | $140/yr 20 years | $44/yr 65 years |
| Iowa | $285/yr 10 years | $138/yr 21 years | $43/yr 67 years |
| Kansas | $325/yr 9 years | $157/yr 18 years | $49/yr 57 years |
| Kentucky | $307/yr 9 years | $149/yr 18 years | $47/yr 59 years |
| Louisiana | $325/yr 8 years | $157/yr 16 years | $49/yr 52 years |
| Maine | $222/yr 13 years | $108/yr 27 years | $34/yr 87 years |
| Maryland | $292/yr 10 years | $142/yr 21 years | $44/yr 66 years |
| Massachusetts | $274/yr 12 years | $133/yr 26 years | $41/yr 82 years |
| Michigan | $271/yr 11 years | $131/yr 23 years | $41/yr 72 years |
| Minnesota | $254/yr 13 years | $123/yr 27 years | $39/yr 86 years |
| Mississippi | $346/yr 7 years | $168/yr 15 years | $52/yr 49 years |
| Missouri | $324/yr 9 years | $157/yr 19 years | $49/yr 60 years |
| Montana | $210/yr 13 years | $102/yr 27 years | $32/yr 87 years |
| Nebraska | $290/yr 10 years | $141/yr 20 years | $44/yr 63 years |
| Nevada | $328/yr 9 years | $159/yr 19 years | $50/yr 62 years |
| New Hampshire | $240/yr 13 years | $116/yr 26 years | $36/yr 83 years |
| New Jersey | $300/yr 12 years | $146/yr 25 years | $46/yr 81 years |
| New Mexico | $279/yr 10 years | $135/yr 20 years | $42/yr 63 years |
| New York | $275/yr 13 years | $133/yr 26 years | $42/yr 84 years |
| North Carolina | $303/yr 9 years | $147/yr 18 years | $46/yr 56 years |
| North Dakota | $246/yr 11 years | $119/yr 24 years | $37/yr 76 years |
| Ohio | $287/yr 10 years | $139/yr 20 years | $43/yr 65 years |
| Oklahoma | $335/yr 8 years | $162/yr 16 years | $51/yr 51 years |
| Oregon — West of Cascades | $202/yr 16 years | $98/yr 33 years | $31/yr 105 years |
| Oregon — East of Cascades | $235/yr 14 years | $114/yr 28 years | $36/yr 91 years |
| Pennsylvania | $281/yr 11 years | $136/yr 23 years | $43/yr 74 years |
| Rhode Island | $271/yr 12 years | $131/yr 26 years | $41/yr 82 years |
| South Carolina | $316/yr 8 years | $153/yr 17 years | $48/yr 55 years |
| South Dakota | $254/yr 11 years | $123/yr 22 years | $39/yr 70 years |
| Tennessee | $301/yr 9 years | $146/yr 18 years | $46/yr 57 years |
| Texas | $344/yr 7 years | $167/yr 15 years | $52/yr 49 years |
| Utah | $280/yr 10 years | $136/yr 20 years | $42/yr 65 years |
| Vermont | $208/yr 14 years | $101/yr 29 years | $31/yr 92 years |
| Virginia | $281/yr 10 years | $136/yr 20 years | $43/yr 64 years |
| Washington — West of Cascades | $186/yr 17 years | $90/yr 36 years | $28/yr 114 years |
| Washington — East of Cascades | $215/yr 15 years | $104/yr 31 years | $33/yr 99 years |
| West Virginia | $288/yr 10 years | $140/yr 21 years | $44/yr 68 years |
| Wisconsin | $250/yr 13 years | $121/yr 26 years | $38/yr 84 years |
| Wyoming | $248/yr 11 years | $120/yr 23 years | $38/yr 73 years |
Simple payback is the middle of the cost range divided by the yearly savings. Savings are for the upgrade on its own; on a full ladder, each rung counts what's left after the rungs before it (how the ladder counts overlap). In California's inland, Central Valley and mountain regions, and east of the Cascades in Washington and Oregon, the savings are raised slightly for the harsher climate.
Your own numbers
Your attic, your bills and your climate decide your figure, and the Upgrade Ladder puts the attic in order with the other upgrades: air sealing comes first, because it costs less and makes the insulation work.
Build your ladder How the estimates are made
Sources
- Savings by depth: Illinois Statewide TRM v14.0, section 5.6.5 (heat-transfer method), checked against the Regional Technical Forum's single-family weatherization workbook v7.2 and the California eTRM.
- Typical heating and cooling shares, where your bills can't measure them: EIA Residential Energy Consumption Survey (RECS 2020).
- Costs: adjusted to your area with RSMeans city cost indices.
- Every step in detail: how the estimates are made.
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