"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.
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.