R-value measures how well a material resists heat flow, and a higher number means better insulation. On a garage door the number is calculated for one door section, not for the installed door with its joints, track and seals. DASMA says a tested whole-door U-factor is the more reliable way to compare doors.
What does R-value mean?
R-value is a measure of thermal resistance. DASMA, the Door and Access Systems Manufacturers Association, says the greater the R-value, the better the insulation. For a garage door, it comes from a calculation using the insulation's thickness and conductivity, plus the air films on each face. Steel facings count as almost nothing.
Does the number describe my whole door?
No. DASMA's technical sheet 163 says the calculated R-value covers the door section only and does not account for section joints or stile attachments. A real door has many joints, plus track, hardware and weather seals. Some parts create a thermal shortcut around the insulation, and thermal breaks and seals resist heat flow.
The whole-door measure is U-factor, tested on a complete installed door under ANSI/DASMA 105. The lower the U-factor, the better. DASMA states the two are not reciprocals, so a U-factor cannot be converted to an R-value or the other way.
Quick facts
| Term | What it measures | Better is | Covers |
|---|---|---|---|
| R-value | Resistance to heat flow, calculated | Higher | One door section |
| U-factor | Heat flow, tested in a lab | Lower | The complete installed door |
Source: DASMA technical data sheet 163. The two values are not comparable to each other.
Polystyrene or polyurethane?
The two common insulation types are rigid polystyrene panels and injected polyurethane foam. Clopay says polystyrene doors have lower R-values than polyurethane doors, that most of its doors are R-10 or above, and that its Intellicore polyurethane doors reach up to R-20.4. Treat the top number as a manufacturer claim and compare the same door on a tested U-factor when one is published.
Clopay also notes that insulated doors are typically quieter, which is a reason to choose insulation apart from the R-number.
Do I need an insulated door?
Clopay says a higher R-value can help your home stay warmer if you have an attached garage, and that insulation helps protect vehicles and stored items and makes the door quieter. A detached garage you rarely use may not need it. Our typical price for a 16x7 steel door is $1,400 to $2,400 non-insulated and $1,800 to $3,400 insulated with short panels. The final price is confirmed after we see the opening. See insulated vs non-insulated doors and insulated garage door cost.
Is a higher R-value worth paying for?
Only if the rest of the door keeps up. A tall R-number on a door with poor seals still leaks air at the edges and bottom. Weather seals and tight section joints matter as much as the foam.
Is the number a calculated R-value or a tested U-factor? Which seals are included at the bottom and sides? Does the quote list the door model and insulation type?
Where we come in
Emil Garage Doors installs insulated garage doors across Southern California, and our city pages also cover California, for example Folsom, Millbrae and Shafter. See new garage doors, then call (213) 340-4232 or send the estimate form, and we will compare doors with the same measure.
Questions people ask
Do I need an insulated garage door?
It helps most when the garage is attached to the house, and insulated doors are typically quieter. A detached garage you rarely use may not need it.
How much does an insulated garage door cost?
Our typical price for an insulated steel 16x7 door is $1,800 to $3,400 with short panels and $1,800 to $3,600 with long panels. The final price is confirmed after we see the opening.
Is an insulated garage door R-value worth it?
A higher R-value helps most on an attached garage, but seals and joints change the real result. Ask for a tested U-factor when one is published.
What is the difference between R-value and U-factor?
R-value is calculated for one door section and higher is better. U-factor is tested on a whole installed door and lower is better. DASMA says they are not reciprocals.
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