Tag Archives: high R-value overhead doors

Barndominium High R-Value Overhead Doors Part II

Continuing the discussion of high R-values in overhead doors from yesterday’s Part I:

Are reported R-values even accurate?

There’s another potential problem with R-values reported by garage-door manufacturers: even if one accepts advertised R-values represent center-of-panel values rather than whole-door values, these numbers are still higher than most insulation experts believe are possible.

Several manufacturers report their polyurethane-insulated door panels have R-values between R-8.6 and R-9.0 per inch — values highly unlikely if not technically impossible, even for door panel centers.

“The R-value of polyurethane decreases with age,” said Yarbrough. “When it is absolutely fresh you might get R-7.5 per inch, but a realistic aged R-value would be lower — perhaps about R-6.5 per inch would be on the high end. I’m not sure I can explain these reported test results. I have seen labs make mistakes before. I think it’s an error.”

What about air leakage?

If garage-door manufacturers ever decide to report whole-door U-factors or whole-door R-values — an important piece of this door-rating puzzle will still be missing. Why? When it comes to thermal performance of garage doors, air leakage matters much more than R-value.

“Garage doors are so leaky that they are difficult to test,” Thoman said. “Their leaks exceed the capabilities of the available testing apparatus.”

When he needed to buy a garage door for his own house, Thoman ignored advertised R-values. “I find it almost offensive that garage-door manufacturers even publish the R-value of the insulation material,” Thoman told Holladay. “I hate it when I see that, because it’s not a representation of the door’s performance. Air leakage is a much more important issue than the R-value of the door.”

Bottom line

Although some garage-door manufacturers have measured whole-door U-factor and air-leakage characteristics of their doors, most won’t release their data. Until they do, purchasers of garage doors have to select their doors based on anecdotes.

Unfortunately, Sectional Garage Doors can’t be installed air tight, there needs to be room for door to slide up and down against door jambs.  These little spaces let cold air draft in and negate much insulating done in door construction.

Some drafts can be stopped with a vinyl weather seal around door and bottom seal, or astragal, can fill in spaces along door bottom depending on how level and even floor is.

Back to why your barndominium needs an insulated overhead door.

More insulation, of course. An uninsulated overhead door is barely a step above an open hole in your wall.

A stronger, more rigid door.  Both polystyrene sandwich doors and polyurethane doors are bonded to steel skin to make them stronger.  They hold up to better to moderate abuse. Be realistic, there is no door which will hold up to a vehicle bumper.

They are much quieter.  This bonding eliminates most rattling which comes with pan (uninsulated steel) doors or as they are referred to as ‘Beer Can Doors”.   

And, while you are at it, make sure your insulated overhead door is appropriately wind load rated: http://www.hansenpolebuildings.com/2014/12/wind-load-rated-garage-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.