How Much Insulation for 1,800 Square Feet?
Bags or rolls
16 bags
1,800 square feet of wall or ceiling, framed at 16 inches on center, with 106.8 square foot bags.
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How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Wall or ceiling area1800 sq ft
- Stud or joist spacing16 in
- Coverage per bag or roll106.8 sq ft
Bags or rolls16 bags
| Gross area | 1,800 sq ft |
|---|---|
| Framing factor at 16 in oc | 90% |
| Cavity area to insulate | 1,620 sq ft |
| Bags at 106.8 sq ft | 16 |
| Coverage bought | 1,709 sq ft |
The material list this produces
| Insulation batts, bags | 16 |
|---|---|
| Vapor retarder, sq ft (if required) | 1,800 |
Coverage per bag compared
Bag coverage is the number that decides this, and it is printed on the bag. Here is the same area at five common coverages.
| Coverage per bag | Bags or rolls | Coverage bought |
|---|---|---|
| 40 sq ft | 41 bags | 1,640 sq ft |
| 50 sq ft | 33 bags | 1,650 sq ft |
| 75 sq ft | 22 bags | 1,650 sq ft |
| 90 sq ft | 18 bags | 1,620 sq ft |
| 106.8 sq ft | 16 bags | 1,709 sq ft |
What else matters here
Eighteen hundred square feet gross, 1,620 of cavity, sixteen bags, 1,709 square feet bought.
Before any of it goes in, seal the holes. Insulation slows heat moving through a surface and does almost nothing about air moving around it, and in a typical older house air leakage is a larger share of the loss than the R value of the walls.
The leaks worth chasing are the big vertical ones rather than the window edges everyone thinks of: the top plates of interior walls, chases around chimneys and ducts, plumbing and wiring penetrations into the attic, recessed lights, the attic hatch, and the rim joist. Canned foam for small gaps, rigid foam and sealant for the big ones, fire rated sealant anywhere near a flue. A day spent there before the batts go in returns more than the bags do.
What this calculator assumes
- Framing takes up roughly 10 percent of a wall at 16 inch on center and 7 percent at 24. Cavity area is reduced accordingly, so you do not buy insulation for the studs.
- Bag coverage varies a lot by R value and width. The default is a common R-13 kraft faced batt bag; read your own bag and change it.
Questions people ask
How many bags of insulation for 1,800 square feet?
Sixteen bags at 106.8 square feet per bag, covering the 1,620 square feet of cavity left after framing.
Should I air seal before insulating?
Yes, and it usually returns more than the insulation does. Insulation slows heat through a surface, it does not stop air moving around it.
Where are the biggest air leaks in a house?
Interior wall top plates, chimney and duct chases, plumbing and wiring penetrations into the attic, recessed lights, the attic hatch and the rim joist.
The insulation calculator takes any dimensions you like and hands back the same list.