What is the R-value difference between polyurethane and polystyrene insulated garage doors in NB?

Polyurethane-insulated garage doors typically provide R-16 to R-18, while polystyrene-insulated doors offer R-8 to R-12 — roughly double the insulating value for polyurethane. In New Brunswick's harsh winter climate, this difference translates to significantly better thermal performance and energy savings if you heat your garage.

Polyurethane insulation is injected as a foam that expands to fill the entire door panel cavity, creating a continuous thermal barrier with minimal air gaps. This injection process bonds the insulation directly to both the interior and exterior steel skins, which also increases the door's structural strength and reduces noise transmission. The higher R-value comes from polyurethane's superior insulating properties — approximately R-6 per inch compared to polystyrene's R-4 per inch.

Polystyrene insulation consists of pre-cut foam boards that are fitted into the door panel sections. While less expensive to manufacture, this method often leaves small air gaps around the edges where the foam meets the panel frame, creating thermal bridges that reduce overall performance. The polystyrene boards are typically 1-2 inches thick, limiting the maximum R-value achievable in a standard residential garage door section.

For New Brunswick's climate conditions, the R-value difference becomes particularly important during the six-month heating season when outdoor temperatures regularly drop to -20°C or colder. An uninsulated garage door (R-2 to R-4) allows massive heat loss and can freeze solid, making manual operation nearly impossible during power outages. The polyurethane door's superior insulation helps prevent this freezing while reducing condensation on the interior surface — a common problem when cold doors meet warm, humid garage air.

Cost considerations reflect the performance difference. Polyurethane-insulated doors cost approximately $300-$800 more than equivalent polystyrene doors, but this premium pays back through reduced heating costs if you heat your garage, and through improved comfort and functionality. The structural benefits of polyurethane's bonding process also mean these doors typically last longer and operate more quietly.

For heated garages or workshops in NB, polyurethane insulation is worth the investment. For unheated vehicle storage, polystyrene provides adequate thermal performance at a lower cost. Either insulated option dramatically outperforms non-insulated steel doors, which become thermal conductors that transfer cold directly into the garage space.

When selecting an insulated garage door, also consider the door's weatherstripping system and bottom seal — even the best-insulated door performs poorly if air leaks around the perimeter. Quality weatherstripping can add another R-2 to R-3 of effective thermal performance by eliminating air infiltration.

Need help finding a garage door contractor who can explain insulation options for your specific situation? New Brunswick Garages can match you with experienced professionals who understand how door insulation performs in our Maritime climate.