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:
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:
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 R-value testing. When I asked Mike Willstead, a technical representative for Raynor, if I could see a copy of Raynor’s test results, he suggested I send him an e-mail. He later e-mailed his response: “I apologize if I misled you. I was informed that this is proprietary information that will not be disclosed.”
The window industry does a much better job
More than a decade ago, responsible window manufacturers realized that the reputation of their industry was being damaged by misleading R-value and U-factor claims. (U-factor is the inverse of R-value; in other words, U=1/R and R=1/U). To address these problems, industry leaders developed a method for testing and reporting whole-window U-factors. The U-factor reported on an NFRC label accurately describes the U-factor of the entire…