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R-49 is the common target for the roof or ceiling in cold and mixed climates. That is about 20 inches of blown fibreglass, 15 inches of blown cellulose, 16 inches of fibreglass batt or about 8 inches of closed-cell spray foam. Air seal the ceiling plane before adding any of it.
An uninsulated steel garage door is about R-2. Enter your door size and panel layout to see how many kit pieces you need and what R-value you'll end up with.
With these inputs:
| Result | Value |
|---|---|
| Door area | 112 sq ft |
| Panel sections to fill | 16 sections |
| Retail kits needed | 1 kit |
| R-value added | R-3.9 |
| Approx door R-value after | R-5.9 |
| Material cost | $31 |
Door area = width × height · Kits = door area ÷ kit coverage (about 112 sq ft) · R added = R-per-inch × thickness
If the garage is attached, heated, or has rooms above it — yes. It typically drops garage temperature swings by 10 to 20 degrees and cuts noise noticeably.
Foam board and reflective kits add only 10 to 20 lbs, which most springs handle. If the door feels heavy or won't stay half open afterwards, have the spring tension adjusted.
They cut radiant heat and take the chill off the panel, which on an uninsulated steel door is a real improvement. What they cannot do is seal the door — the gaps around the perimeter and under the bottom seal usually leak more energy than the panel conducts. Do the weatherstripping at the same time or most of the benefit escapes around the edges.
Only if the springs are adjusted for the extra weight. A kit adds meaningful mass to each panel, and a door that was balanced before will be heavy afterwards — hard on the opener and, on a torsion spring system, potentially unsafe. Spring adjustment is genuinely dangerous to do yourself; this is the part to hand to a door technician.
Far less than a wall, because the panel is thin and the perimeter leaks. Retrofit kits are limited by the depth inside the panel ribs. Treat the door as damage limitation rather than as insulation: it is worth doing if you are heating the garage, and it will never match the wall it sits in.
Need the whole roof at once? The free roofing calculator works out roof area, squares, shingle bundles, underlayment, drip edge, ridge cap and installed cost from one set of measurements.