Insulation for Garage Walls
Free calculator with pre-filled dimensions • Updated March 2026
A 24×24 garage (576 sq ft of wall space) needs about 12 batts of R-15 fiberglass batt insulation (48 sq ft coverage each).
Open calculator with these dimensions →Garage Wall Insulation Guide
Insulating garage walls is essential if you heat/cool the garage as a workshop, or if the garage shares a wall with living space (which is a code requirement). A standard 24×24 garage with 9-foot walls has about 576 square feet of insutable wall area after subtracting the garage door opening.
Material Options
| Type | R-Value | Quantity | Cost (2026) |
|---|---|---|---|
| Fiberglass batts (R-13) | R-13 (3.5") | 16 rolls | $320–$480 |
| Fiberglass batts (R-15) | R-15 (3.5") | 18 rolls | $396–$540 |
| Mineral wool (Rockwool) | R-15 (3.5") | 18 bags | $500–$720 |
| Rigid foam (1.5" XPS) | R-7.5 | 18 sheets | $360–$540 |
Pro Tips
- Mineral wool (Rockwool) is worth the premium in garages. It's fire-resistant (up to 2,150°F), water-resistant, and doesn't lose R-value when damp. In a garage environment with fumes, moisture, and fire risk, it's the safest choice.
- The garage door is the biggest thermal gap. Even fully insulated walls lose much of their benefit if the garage door is uninsulated. A garage door insulation kit ($100–$200) can cut heat loss by 40%.
- Don't forget the ceiling. If living space is above the garage, the ceiling must be insulated to R-30 or higher per code. Use R-30 batts between ceiling joists.
Frequently Asked Questions
What R-value for garage walls?
R-13 minimum for 2×4 walls, R-15 if using higher-density batts. If the garage wall is adjacent to living space, local code may require specific R-values — typically R-13 to R-21 depending on climate zone.
Is it worth insulating a garage?
Yes, especially if you use the garage as a workshop or it shares a wall with your house. Insulated garages stay 20–30°F warmer in winter and cooler in summer. A heated insulated garage uses 50–70% less energy than an uninsulated one.