Insulated garage doors: why an R-value on a quote is not the whole story

What the number on the quote is describing

A salesperson tells you a door is R-something, and the number sounds like it settles the question. It does not, and the reason is a distinction that DASMA sets out in its technical data sheet 163. R-value, it says, is calculated for a door section only. U-factor is tested on the complete installed door, under the standard ANSI/DASMA 105. The two, DASMA says, are not comparable, and U-factor and R-value are not reciprocals. It adds that a section R-value should not be used for door assemblies.

Read that carefully, because it changes how you read a quote. A section is one panel of the door. The door is the panel plus the joints between panels, the edges, the seal, the track and the hardware. Heat finds its way through all of them. So a figure for the section describes one part of the door, and the figure for the installed door describes what you actually live with. Neither number is a promise about your heating bill. The useful question is what the quoted figure measures, and for which part of the door.

What to ask a company to show

Because the two measures are different, the questions are specific.

Ask which measure the quote gives. If the quote says R-value, ask whether it is for a section and what test or calculation produced it. If it says U-factor, ask whether it is for the complete door as installed, and at what size, since DASMA describes the U-factor as tested on the installed door.

The document matters more than the sentence. A thermal figure should come from the maker’s published data or a test report for the door model. Ask for it by model name, and keep it with the contract, so that the figure on paper can be checked against the door that arrives.

Next, find out what the figure covers: the bottom seal, the joint seals between sections, and any weather seal at the top and sides. DASMA’s sheets do not answer that for a particular model.

The quote should also state what separates the insulated door from the plain one. It should name what is in the section, such as a layer of insulation, and how the section is built. Do not accept a bare number. When you compare companies, write each one’s model name and quoted figure side by side.

The ENERGY STAR question

We could not confirm that a garage door can carry an ENERGY STAR label, so we will not say that one can, or that one does. If a company tells you a door is, ask it to show the listing.

Michigan energy code and garage doors

We found no requirement for garage doors in the Michigan residential energy code material we could reach, and the 2021 update to the residential energy provisions is on hold under a court order that LARA describes. We have not checked every provision of the 2015 energy code text, so we do not say that none exists. If a company says your city requires a particular thermal figure for a door, ask where it is written, and ask your city’s building department. State law says construction or alteration of a building needs a permit unless the act or code provides otherwise, and whether a garage door swap needs one is a question for your city. See the permit guide.

Insulation and winter use

DASMA’s climate sheet, TDS 190, says doors left open for extended periods face more temperature, moisture and air-quality variation, and that in climates with extreme heat or cold and frequent precipitation doors should be kept closed where possible, and lubricated as the manufacturer says. It does not say that an insulated door changes that advice. Our winter guide covers the practical checks.

An attached garage

If your garage is attached to the house, the door you choose is one of the things between the cold and the living space. One legal point does apply. Michigan law says a carbon monoxide device is to be located near bedrooms and in areas of the dwelling adjacent to an attached garage, where it is required at construction or renovation under a permit. That concerns the dwelling and the permit, not the door, but a garage renovation that needs a permit can bring it in. Ask the building department whether your project is one.

Insulation does not change the other rules

Whatever the thermal figure, the other facts about a replacement stay the same. DASMA says installing a garage door can be very dangerous and is not recommended for a novice. It says a new door on the old track may not fit, because the track and sections work together. And it says the building department with authority in your area is the sole and final determiner of the wind load requirements for the door, so a thick, well-insulated door still has to suit the opening and the local rule. See the wind rating guide for the questions to ask.

A short list for the next quote

• Which measure is quoted, R-value or U-factor, and for what: a section or the installed door?
• Where is the figure from: a model’s published data or a test report?
• What is in the door that makes it insulated?
• Does the figure include the seals?
• Is the track new, and who installs it?

If the company answers in numbers without documents, treat the numbers as sales talk and ask for the paper. Keep the written answers with the contract, and photograph the label on the door after it is installed so the model can be matched to the paper. You can also look up the model name on the maker’s own website and compare what it publishes with what the salesperson said. The repair or replace tool and the door replacement page have more on weighing a new door against a repair, and the cost evidence we do and do not hold is in the cost guide.