If you’re shopping for a garage door, the door’s energy performance may not matter — especially if you don’t heat your garage. However, there are a few reasons why you might be looking for a well-insulated, draft-free garage door:
- A good overhead door on an attached garage can keep the garage — and therefore the house — a little warmer than a leaky door.
- Since cars can be hard to start in sub-zero weather, homeowners in very cold climates — even those with unheated garages — may want a garage door that limits heat loss.
- If the garage is used for vehicle maintenance or woodworking projects, it may occasionally be heated.
So, how do you tell a high-performance garage door from a lemon?
“We sell high R-value doors!”
Many garage-door manufacturers advertise the R-values of their doors:
- CEDO advertises doors with R-17.09 polyurethane insulation.
- Clopay advertises that some of its doors are R-17.2.
- Overhead Door advertises that “a 17.5 R-value makes the 490 Series among the most thermally efficient doors you can buy.”
- Raynor advertises “R-values from 12.0 – 18.0.”
- Wayne-Dalton advertises garage doors with R-15 insulation.
Unfortunately, these advertised R-values are almost meaningless.
Advertised R-values are inaccurate, irrelevant — or both
To determine the thermal performance of a garage door, you need to know two things:
The R-values that are trumpeted by garage-door manufacturers are measured at the center of one of the door panels. No manufacturer, as far as I can determine, reports the R-value of the entire door assembly (including the panel edges, the seams between panels, and the perimeter of the door) in their promotional materials. Moreover, manufacturers’ reported R-values tell us nothing about air leakage.
Most garage-door manufacturers are reluctant to share actual laboratory reports showing the results of…