"Best" depends on whether you're buying a new door or upgrading the one you've got. Here's how the real options stack up for our climate.
Factory polyurethane (the top pick)
Poly is injected as a liquid that expands and bonds to the whole panel, so it fills every gap and stiffens the door. You get the highest R-value (R-12 to R-18), the quietest operation, and the best dent resistance. For an attached DFW garage, this is what we recommend.
Factory polystyrene (the budget layer)
Polystyrene is a foam board slid into the door. It helps — roughly R-6 to R-9 — and costs less, but it doesn't bond to the panel, so it's not as quiet or as strong as poly. Fine for a mild need; underwhelming in a July garage.
DIY foam-board kits
For a door you're keeping, rigid foam-board kits give the most real insulation per dollar. They take an afternoon to fit. See our step-by-step DIY guide.
DIY reflective/radiant kits
Thin reflective kits are the easiest to install and are good at bouncing radiant heat, but they add less R-value than foam board. A reasonable choice if easy install matters more than maximum insulation.
The honest bottom line
If you're replacing the door, get factory poly — it's only a little more and worth it. If you're keeping your door, foam board is the best DIY value. Either way, fix the weather seal so drafts don't undo it. Compare new-door options in our designer.
R-value vs. U-factor: which one measures a door
For garage doors, R-value and U-factor are not the same thing, and the difference matters. A door’s advertised R-value is calculated at the center of one section, not measured across the whole door. U-factor is the measured, whole-door number that building codes use — and for U-factor, lower is better.
- R-value on a garage door is a calculation of one section’s center; DASMA says that method ‘should not be used for garage door assemblies.’ DASMA TDS-163
- U-factor is the whole-door measurement (ANSI/DASMA 105) that captures joints, seals and hardware — and lower is better. DASMA TDS-163 Amarr
- For garage doors, R-value ≠ 1/U-factor. They are not reciprocals. DASMA TDS-163
- Clopay’s polyurethane Intellicore doors range from about R-6.3 to R-20.4 depending on the line. Clopay
- ENERGY STAR does not certify garage doors at all — it covers windows, entry doors and skylights, rated by U-factor. An ‘ENERGY STAR-rated garage door’ claim is incorrect. ENERGY STAR
| R-value | U-factor | |
|---|---|---|
| What it measures | Center of one door section (calculated) | The whole installed door (measured) |
| Test method | Component calculation | ANSI/DASMA 105 |
| Used by building codes | No (not for assemblies) | Yes |
| Better when… | Higher | Lower |
“U-factor provides the highest degree of confidence when evaluating and comparing the thermal performance of garage door assemblies.”
In Texas heat, an attached garage’s door is part of your home’s thermal envelope. DOE guidance focuses on air-sealing and insulating between an unconditioned garage and the living space, and defers R-value targets to the IECC climate-zone tables rather than a single garage-door number. U.S. DOE
Sources: DASMA TDS-163 · Amarr · Clopay · ENERGY STAR · U.S. DOE
Key takeaways
- Best overall: a factory polyurethane door (R-12 to R-18) — highest R-value, quietest, strongest.
- Polystyrene is a cheaper factory layer but adds less and isn't bonded to the panel.
- Best DIY value: rigid foam-board kits; reflective kits are easier but add less.
- Fix the weather seal too, or edge drafts undo the insulation.
- Replacing the door? Factory poly is only a little more and worth it.