Factory-insulated garage doors commonly use polyurethane or polystyrene foam. Retrofit kits may use rigid foam board, faced fiberglass or reflective material. Compare the complete installed product and its added weight: reflective foil needs an air space, and a kit is not equivalent to a factory-insulated door.
Compare the construction, not just the material name
| Type | Typical use | Main check |
|---|---|---|
| Polyurethane foam | Factory-filled insulated door sections. | Quoted model's thermal rating and section construction. |
| Polystyrene / rigid foam board | Factory sections or an approved retrofit kit. | Thickness, facing, retention and compatibility. |
| Faced fiberglass | Some door retrofit kits. | Door approval, facing and secure retention. |
| Reflective material | A designed reflective insulation system. | Required air gap and the tested installed assembly. |
Polystyrene is itself a foam-board material, so listing it and foam board as unrelated insulation types can confuse the choice. Department of Energy guidance explains that reflective surfaces need an adjacent air space to work as intended.
R-value and real garage comfort
R-value measures resistance to heat flow. Compare like-for-like ratings: insulation material, a section and a complete door assembly are not automatically the same measurement. Seals, glazing, air leakage and the rest of the garage also affect temperature.
Can you add insulation to your existing door?
Use only a kit compatible with the door and its care instructions. Added weight can change counterbalance requirements, so have the installer confirm suitability before attaching it. Do not spray household foam into moving sections or adjust springs to compensate.
Facing and fire-performance requirements depend on the product and installation. Do not assume all steel doors accept any insulation or that every garage needs the same vapor barrier.
See garage door insulation for retrofit considerations and insulated garage doors for factory-built choices. Call (916) 838-8182 to discuss a door replacement.
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