Tag Archives: R-value overhead doors

Barndominium High R-Value Overhead Doors Part I

Barndominium High R-value Overhead Doors
When my lovely bride and I had our post frame building shouse (shop house aka barndominium) constructed, energy efficiency was important for us. Then Hansen Pole Buildings was ordering our overhead doors through my friend David Vance, owner of Rainer Building Products in Western Washington. I approached David with our needs for doors and he recommended C.H.I. doors with an advertised R value of 17.19 for an 1-7/8” thick polyurethane insulated door.
Unfortunately, these advertised R-values are almost meaningless.

Advertised R-values are inaccurate, irrelevant — or both

To determine thermal performance of a garage door, you need to know two things:

A door’s leakiness, and entire door assembly R-value or U-factor.

R-values claimed by garage-door manufacturers are measured at door panel centers. Apparently no manufacturer reports R-value of their entire door panel (including panel edges, seams between panels, and door perimeter) 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 results of R-value testing.

“For marketing purposes, the garage door people get a measurement on the center of panel,” said David Yarbrough, a research engineer and insulation expert at R&D Services in Cookeville, Tennessee. “The overall R-value of the entire door might be quite a bit less — in extreme cases, it may be half — of the R-value of the center of the panel. Not everyone approves of this kind of marketing. It’s been a hot debate in recent years.”

In fact, real percentages turn out to be much less than half.

Actual R-values are one-third the advertised values

Although it’s hard to obtain actual test results reporting whole-door U-factors of “tested installed doors,” Martin Holladay managed to obtain one report on a garage door from Clopay, and another on a garage door from Overhead Door.

Clopay provided test results for their model 3720 five-panel garage door. According to Mischel Schonberg, Clopay’s public relations manager, their door is insulated with two inches of polyurethane foam. Schonberg wrote, “This model is the commercial version of our residential model 9200 and has the same construction.”

While Clopay advertises their 9200 door is R-17.2 — presumably, a claim based on a center-of-panel measurement — actual test report for an installed door shows R-6.14.
While Overhead Door advertises their model 494/495 Thermacore door has an R-value of 17.5 — a claim, like competitors’ claims, is presumably based on a center-of-panel measurement — installed door test reports show a U-factor of 0.16, equivalent to R-6.25.

Based on these only two test reports Martin was able to track down, it seems logical to conclude R-value of a garage door is about one-third of R-value claimed in a manufacturer’s brochure.

All over the map

Mike Thoman, director of thermal testing and simulation at Architectural Testing Incorporated, a Pennsylvania laboratory, has tested many garage doors.

“The assembly R-values are not going to be nearly as good as the R-value of the material would indicate,” Thoman told Holladay. “When you compare the assembly R-value to the material R-value, the percentages are all over the map. The percentage is a function of how the joints in the panels are made, and whether any attempt was made to provide for thermal breaks at panel edges — a lot of different things. Some products have a lot of insulation in the panel but have everything else wrong. We’ve also seen doors that do everything right. There’s really a wide, wide range.”

Come back tomorrow for Part II in this discussion of R-values in overhead doors.

High R Value Overhead Doors

If your new post frame building will only ever be cold storage, then an insulated overhead door just might be all your will ever want, or need. For most people, I encourage them to go with insulated doors, just on the oft chance someone down the line will have different ideas. Insulated overhead doors do tend to ‘feel’ stiffer and to rattle less in a strong breeze.

But what about the R-values of those doors?

Consider this – insulated overhead doors are using polyurethane, which has an initial R-value of maybe as much as 7.5 per inch, however the R-value does decrease with age so a more realistic high end “aged” R-value would probably be closer to 6.5 per inch.

Several overhead door manufacturers report their polyurethane insulated door panels to be as much as R-9.0 per inch, which is both highly unlikely and technically impossible to achieve!

One overhead door company in Maine actually sent an overhead door with an insulated 1-3/8 inch thickness which was advertised as being R-12.76 to be independently tested. The door came back as being actually only R-7.83!

This same company now has what they call their “R-value challenge” to manufacturers. They will write a check to any manufacturer who can prove a 1-3/8 inch thick door is R-12! They have not had to pay yet, and probably never will.

To determine the true thermal performance of an insulated overhead door, one would need to know two things, the door’s ‘leakiness’ and the R-value of the entire door assembly.

The R-values used by garage door manufacturers are measured at the center of the panels, and it appears no one is reporting the R-value of the entire assembly which would include the panel edges, seams between panels and the perimeter of the door.

In comparison of manufacturer’s R-value claims with test reports of the installed doors as part of a system, it appears the R-value of a garage door installed is going to be about one-third of the value claimed in the manufacturer’s brochures!

Even if garage door manufacturers do decide to report whole door R-values, the big piece will still be missing – when it comes to thermal performance of garage doors, air leakage matters more than R-value.

Most important when looking at the thermal performance of an overhead door is a design which minimizes air leakage, with good gaskets between the panels, heavy-duty weatherstripping at the bottom of the door and weather seals up the sides and across the top of the openings.