R-value measures how well one door section resists heat flow. U-factor measures the whole door, and the two are not simple opposites. A higher R-value is better, and polyurethane foam usually beats polystyrene, but seals and the garage itself matter too. Insulation helps most when the garage is attached or has rooms above it.
What does R-value actually tell me?
R-value is the old rating manufacturers use for resistance to heat flow. Amarr explains that R-value accounts for an individual door section, not the whole assembly. A higher number means better insulation for that section.
That is why one door can look great on a brochure and still lose heat at the edges. The panel is only part of the story.
What is U-factor, and which number should I use?
U-factor measures heat flow through the whole door as installed. For U-factor, a lower number is better. DASMA, the garage door trade association, has been moving the industry toward U-factor, and its Thermal Performance Verification Program covers it. Amarr points out that R-value and U-factor are not reciprocals for garage doors, so you cannot flip one to get the other.
When you compare quotes, ask for the U-factor first and the section R-value second. If a quote lists only one, ask for the other.
Quick answers to common questions
| Question | Short answer |
|---|---|
| Is higher R-value better? | Yes, for the section. It does not cover gaps and seals. |
| Is lower U-factor better? | Yes. It covers the whole door. |
| Foam or polystyrene? | Clopay says polyurethane gives the highest R-value per inch, polystyrene gives good value per dollar. |
| Does the garage need insulation? | More useful if it is attached or has rooms above, says Amarr. |
| Can I improve an old door? | Amarr suggests improving the weather seal first. |
Based on the manufacturer pages listed in the sources.
Polyurethane or polystyrene?
Polyurethane foam
- Highest R-value per inch of the common insulation types, per Clopay
- Costs more
- Bonds the steel skins to the core
Polystyrene panels
- Cost-effective and a good R-value per dollar spent, per Clopay
- Thinner R-value per inch
- A sound pick for a detached or unheated garage
Fiberglass insulation has a lower R-value and Clopay notes it can settle over time, which can reduce its performance. Look at the construction of the panel, not only the number on the label.
When is insulation worth paying for in a Utah garage?
Amarr says a low-U-factor door can reduce heating and cooling needs, especially when the garage is attached to the house or has rooms above it. That is the case where cold winter nights in the garage can cool the floor above and the wall next to it.
A detached garage used only for storage is a different story. If you do not heat it, a basic steel door with good seals may be enough. If you work in it or keep a workshop there, insulation gives a more even temperature.
Amarr also says recommended values depend on the climate zone and local building codes, so ask your city and your HOA what applies before you choose.
Do not forget the seals
A door with a good panel and a worn bottom seal still lets cold air under it. Check that the seal sits tight against the floor and that the side and top weatherstripping is not cracked or flat. Replacing it is a small job compared with a new door.
If you already have a door that moves well, a seal may be all you need. If the door is dented, noisy or worn out, a new insulated door and new hardware may be the better use of money.
What it costs
Our approved price for an insulated steel door, short panel, 16x7, installed, is $1,800 to $3,400. A long panel door is $1,800 to $3,600. The final price depends on the size, windows and color, and we confirm it after we see the opening. See new garage doors for the full list, and read Utah HOA and city rules before you order.
Who to call
Emil Garage Doors installs new insulated doors and repairs springs, cables and openers in Utah, including Bountiful, Logan and Ogden. Call or send your details and the door size, and we will quote a door and list the insulation type, so you can compare it to other quotes.
Questions people ask
What R-value should a garage door have in Utah?
There is no single number. Amarr says recommended values depend on climate zone and local codes. Ask for the U-factor and the section R-value, and ask your city what applies.
Is polyurethane better than polystyrene for a garage door?
Clopay says polyurethane gives the highest R-value per inch of any insulation material, and polystyrene gives a good R-value per dollar. Polyurethane costs more.
Do I need an insulated garage door if my garage is detached?
Not always. Amarr says insulation helps most when the garage is attached or has rooms above it. A detached garage that you do not heat may do fine with a basic door and good seals.
Can I make my current garage door warmer?
Start with the weather seal at the bottom, sides and top, which Amarr recommends for an existing door. If the panels are worn or damaged, a new door may be the better choice.
Read next
Sources
- Amarr: Garage door R-value and U-factor 101 (R-value is for a section, U-factor for the whole door; attached garages)
- Clopay: Improve energy efficiency with insulated garage doors (polyurethane and polystyrene, steel skins)
- DASMA: Technical Data Sheet 196 on U-factor and the Thermal Performance Verification Program