· by Michael Blair, Nashville's Garage Door
Insulated doors cost more and are sold on energy savings. Whether that is real depends almost entirely on what is on the other side of the garage wall and above the garage ceiling.
When it matters
An attached garage sharing walls with living space, and especially one with a bonus room above, benefits meaningfully. That bonus room is the hottest room in most Nashville houses in August.
A garage used as a workshop or gym also benefits directly, because you are conditioning it.
When it does not
A detached garage used for parking gains very little. The door is one surface of an otherwise uninsulated building, and insulating it alone changes almost nothing.
The same applies to an attached garage whose shared wall and ceiling are already well insulated and air sealed — the door is then not the weak point.
- Attached garage with rooms above: worthwhile
- Detached parking garage: minimal benefit
- Workshop or gym use: worthwhile
- Weatherstripping and the bottom seal matter as much as R-value
- Insulating the ceiling above usually beats insulating the door
What R-value on a door means
Manufacturers quote R-value differently, sometimes for the panel and sometimes for the whole assembly including frame and seals. Compare like with like, and treat headline numbers with some caution.
Polyurethane-injected doors generally outperform polystyrene panels at the same nominal thickness and are also considerably more rigid.
The cheaper wins first
Weatherstripping around the perimeter and a good bottom seal cost very little and close the gaps that let outside air straight in. A poorly sealed insulated door underperforms a well-sealed uninsulated one.
And insulating the garage ceiling, where there is living space above, does more than the door in almost every Nashville house.