How Much Insulation for 700 Square Feet?
Bags or rolls
6 bags
700 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 area700 sq ft
- Stud or joist spacing16 in
- Coverage per bag or roll106.8 sq ft
Bags or rolls6 bags
| Gross area | 700 sq ft |
|---|---|
| Framing factor at 16 in oc | 90% |
| Cavity area to insulate | 630 sq ft |
| Bags at 106.8 sq ft | 6 |
| Coverage bought | 641 sq ft |
The material list this produces
| Insulation batts, bags | 6 |
|---|---|
| Vapor retarder, sq ft (if required) | 700 |
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 | 16 bags | 640 sq ft |
| 50 sq ft | 13 bags | 650 sq ft |
| 75 sq ft | 9 bags | 675 sq ft |
| 90 sq ft | 7 bags | 630 sq ft |
| 106.8 sq ft | 6 bags | 641 sq ft |
What else matters here
Seven hundred square feet gross, 630 of cavity, six bags. Six bags buys 641 square feet against 630 needed, so this is one of the sizes where the round up lands tight. Buy seven.
The other decision at this size is faced or unfaced. A kraft faced batt has a paper flange that staples to the studs and a bitumen coating that acts as a vapor retarder. An unfaced batt is friction fit and has no retarder at all.
If you use faced batts, the paper goes toward the heated side of the wall, which in most of the country means facing into the room. Get it backwards in a cold climate and the retarder sits on the cold side, where it stops moisture escaping outward and collects it in the cavity instead. In hot humid climates the right answer is often no interior vapor retarder at all, so unfaced batts and a separate air barrier, because there the vapor drive runs the other way for most of the year.
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 700 square feet?
Six bags covers 641 square feet against 630 of cavity, which is tight. Seven bags is the safer order.
Which way does the paper on insulation face?
Toward the heated side, which in most of the country means into the room. The paper is a vapor retarder and it belongs on the warm side of the assembly.
Should I use faced or unfaced batts?
Faced in most heating climates, because the kraft paper acts as the vapor retarder. In hot humid climates unfaced is often better, since an interior retarder traps moisture moving inward.
The insulation calculator takes any dimensions you like and hands back the same list.