Insulation Calculator
US & CanadaEnter the area and pick the insulation to get the packages or bags to buy, straight from the maker's coverage chart.
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From the data sheet
Coverage is copied from each maker's own sheet. Packs vary by store and facing, so check the square footage on the bag you buy.
How the insulation maths works
- Batts = area × (1 + allowance) ÷ square feet per package, rounded up
- Blown-in = area ÷ 1,000 × the maker's minimum bags per 1,000 sq ft, rounded up
Batt coverage is the area printed on the package, which is the batt area. In a framed wall the studs take some width too, so a package covers a little more wall than that and the count leans slightly over. Blown-in has no extra allowance: the maker's minimum bag count at the minimum settled depth is what the label R-value rests on.
Recommended R-values in the US
From ENERGY STAR's retrofit table, which it bases on the 2021 IECC, Table R402.1.3. Find your zone on the ENERGY STAR climate zone map.
| Zone | Attic, uninsulated | Attic, with 3 to 4 in | Floor |
|---|---|---|---|
| 1 | R30 | R25 | R13 |
| 2 | R49 | R38 | R13 |
| 3 | R49 | R38 | R19 |
| 4A and 4B | R60 | R49 | R19 |
| 4C, 5 and 6 | R60 | R49 | R30 |
| 7 and 8 | R60 | R49 | R38 |
ENERGY STAR gives walls as advice rather than one number: blow insulation into empty cavities when siding comes off, and add R5 sheathing in zone 3, or R5 to R10 in zones 4 to 8.
Minimum RSI in Canada (NBC 2020)
National Building Code of Canada 2020, Table 9.36.2.6.-A, for houses without a heat recovery ventilator. Zones go by heating degree-days. These are effective values for the whole assembly; R is RSI × 5.678, worked out by us, as the code prints RSI only.
| Zone | Degree-days | Ceiling below attic | Walls | Floors over unheated space |
|---|---|---|---|---|
| 4 | under 3000 | RSI 6.91 (R39.2) | RSI 2.78 (R15.8) | RSI 4.67 (R26.5) |
| 5 | 3000 to 3999 | RSI 8.67 (R49.2) | RSI 3.08 (R17.5) | RSI 4.67 (R26.5) |
| 6 | 4000 to 4999 | RSI 8.67 (R49.2) | RSI 3.08 (R17.5) | RSI 4.67 (R26.5) |
| 7A | 5000 to 5999 | RSI 10.43 (R59.2) | RSI 3.08 (R17.5) | RSI 5.02 (R28.5) |
| 7B | 6000 to 6999 | RSI 10.43 (R59.2) | RSI 3.85 (R21.9) | RSI 5.02 (R28.5) |
| 8 | 7000 or more | RSI 10.43 (R59.2) | RSI 3.85 (R21.9) | RSI 5.02 (R28.5) |
With an HRV the code allows less in some zones (Table 9.36.2.6.-B), for example walls at RSI 2.97 in zones 5 to 7A. Provinces adopt the NBC on their own timetable, and NBC 2025 has been published, so confirm the edition with your building department.
Ontario uses its own SB-12. In package A1 (Zone 1), as published by the Ontario government in 2016, attics need nominal R60 (effective R59.22) and above-grade walls nominal R22 (effective R17.03). Nominal is the batt's own R-value.
Coverage per package
| Product | Fits | Coverage |
|---|---|---|
| R-13 fiberglass batt, 15 in (Johns Manville) | 2 × 4 walls, 16 in on centre | 106.56 sq ft a package |
| R-13 fiberglass batt, 23 in (Johns Manville) | 2 × 4 walls, 24 in on centre | 163.39 sq ft a package |
| R-19 fiberglass batt, 15 in (Johns Manville) | 2 × 6 walls, 16 in on centre | 87.18 sq ft a package |
| R-19 fiberglass batt, 23 in (Johns Manville) | 2 × 6 walls, 24 in on centre | 133.68 sq ft a package |
| R-30 fiberglass batt, 16 in (Johns Manville) | Attic floors and ceilings, 16 in on centre | 58.66 sq ft a package |
| R-30 fiberglass batt, 24 in (Johns Manville) | Attic floors and ceilings, 24 in on centre | 88 sq ft a package |
| R-38 fiberglass batt, 16 in (Johns Manville) | Attic floors and ceilings, 16 in on centre | 42.66 sq ft a package |
| R-38 fiberglass batt, 24 in (Johns Manville) | Attic floors and ceilings, 24 in on centre | 64 sq ft a package |
| R14 Comfortbatt, 16 in o.c. (ROCKWOOL) | 2 × 4 walls, 16 in on centre | 59.7 sq ft a package |
| R22 Comfortbatt, 16 in o.c. (ROCKWOOL) | 2 × 6 walls, 16 in on centre | 39.8 sq ft a package |
| R22 Comfortbatt, 24 in o.c. (ROCKWOOL) | 2 × 6 walls, 24 in on centre | 37.5 sq ft a package |
| R24 Comfortbatt, 16 in o.c. (ROCKWOOL) | 2 × 6 walls, 16 in on centre | 29.4 sq ft a package |
| R24 Comfortbatt, 24 in o.c. (ROCKWOOL) | 2 × 6 walls, 24 in on centre | 29.7 sq ft a package |
| R-30 blown fiberglass (Owens Corning AttiCat) | Open attic floors | 14.6 bags per 1,000 sq ft at 10.75 in |
| R-38 blown fiberglass (Owens Corning AttiCat) | Open attic floors | 19 bags per 1,000 sq ft at 13.5 in |
| R-49 blown fiberglass (Owens Corning AttiCat) | Open attic floors | 25 bags per 1,000 sq ft at 17 in |
| R-60 blown fiberglass (Owens Corning AttiCat) | Open attic floors | 31.5 bags per 1,000 sq ft at 20.5 in |
| R-30 blown cellulose (Greenfiber SANCTUARY) | Open attic floors | 36.5 bags per 1,000 sq ft at 8.3 in |
| R-38 blown cellulose (Greenfiber SANCTUARY) | Open attic floors | 50.1 bags per 1,000 sq ft at 10.4 in |
| R-49 blown cellulose (Greenfiber SANCTUARY) | Open attic floors | 68.5 bags per 1,000 sq ft at 13.3 in |
| R-60 blown cellulose (Greenfiber SANCTUARY) | Open attic floors | 83.5 bags per 1,000 sq ft at 16.1 in |
Sources: Johns Manville Fiberglass Manufacturers Fact Sheet (BID-380 12/19); ROCKWOOL Residential Building Product Guide, Canada; Owens Corning AttiCat Product Data Sheet (May 2026); Greenfiber SANCTUARY attic chart. Blown cellulose charts depend on the blowing machine, so follow the chart on the bag you buy.