How Much Insulation for 1,100 Square Feet?
Bags or rolls
10 bags
1,100 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 area1100 sq ft
- Stud or joist spacing16 in
- Coverage per bag or roll106.8 sq ft
Bags or rolls10 bags
| Gross area | 1,100 sq ft |
|---|---|
| Framing factor at 16 in oc | 90% |
| Cavity area to insulate | 990 sq ft |
| Bags at 106.8 sq ft | 10 |
| Coverage bought | 1,068 sq ft |
The material list this produces
| Insulation batts, bags | 10 |
|---|---|
| Vapor retarder, sq ft (if required) | 1,100 |
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 | 25 bags | 1,000 sq ft |
| 50 sq ft | 20 bags | 1,000 sq ft |
| 75 sq ft | 14 bags | 1,050 sq ft |
| 90 sq ft | 11 bags | 990 sq ft |
| 106.8 sq ft | 10 bags | 1,068 sq ft |
What else matters here
Eleven hundred square feet gross, 990 of cavity, ten bags, 1,068 square feet bought.
Most of the labor on a job this size is not hanging full batts, it is the cutting. Cut batts about half an inch wide of the cavity so they friction fit rather than compress, cut them on a scrap of plywood with a long blade and a straightedge, and cut from the back so the facing tears cleanly.
Wiring and boxes are where the R value actually goes. Split the batt to its full depth and pass half behind the wire and half in front of it rather than shoving the whole thing behind, and cut a pocket around each electrical box so the insulation meets the box on all four sides. A batt bulging over a wire leaves a void the width of the cavity, which is a much bigger hole than it looks.
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 1,100 square feet?
Ten bags at 106.8 square feet per bag, covering the 990 square feet of cavity left after framing.
How do you insulate around electrical wires?
Split the batt through its thickness and put half behind the wire and half in front. Stuffing the whole batt behind the wire leaves a void across the cavity.
How do you cut insulation batts?
Slightly wide of the cavity so they friction fit, on a scrap of plywood, with a long sharp blade and a straightedge, cutting from the back.
The insulation calculator takes any dimensions you like and hands back the same list.