What is the best garage door insulation R-value for the Maritime climate in NB?

For New Brunswick's Maritime climate, the best garage door insulation R-value is R-16 to R-18 for heated garages and workshops, with R-12 as the minimum worthwhile investment. The garage door is the largest opening in your garage and the single biggest source of heat loss — a standard non-insulated steel garage door has an R-value of roughly R-1 to R-3, which in NB's climate is essentially no insulation at all.

To understand why the garage door matters so much, consider the surface area involved. A standard 16-foot double garage door is approximately 112 square feet of surface area — larger than most garage walls. When winter temperatures in NB drop to -20 to -30 degrees Celsius and you are trying to keep a heated garage at workshop temperature (10 to 15 degrees Celsius), the temperature differential across that thin, uninsulated door can exceed 40 degrees. The heat loss through 112 square feet of R-2 door at that differential is enormous, and your heater runs constantly trying to compensate. Upgrading to an R-16 door reduces heat loss through that surface by approximately 85%, which translates directly into lower heating costs and a more comfortable garage.

Insulated garage doors come in two main construction types, and the type matters as much as the R-value number. Polystyrene-insulated doors use rigid foam panels inserted between the steel skins. They are lighter, less expensive, and typically offer R-values of R-6 to R-12. Polyurethane-insulated doors use injected foam that bonds to both steel skins, creating a stronger, quieter, and better-insulated door with R-values of R-12 to R-18. For NB's climate, polyurethane-injected doors are the better investment — they provide higher R-values in a thinner profile, they are significantly stronger and more dent-resistant than polystyrene doors, and the foam bonding to both skins eliminates the thermal bridging that occurs at the steel stiles and rails of polystyrene doors.

In terms of actual products and pricing in the NB market, expect to pay the following for a 16-foot double garage door, installed: a non-insulated steel door runs $1,200 to $2,500, a polystyrene-insulated door (R-6 to R-12) runs $1,500 to $2,800, and a polyurethane-insulated door (R-16 to R-18) runs $1,800 to $3,500. The price difference between a non-insulated and an R-16 insulated door is typically $500 to $1,000 — a modest premium that pays for itself within 2 to 4 heating seasons if you heat your garage. For a single 9-foot garage door, subtract roughly 30-40% from these prices.

Beyond R-value, the weatherstripping and bottom seal on your garage door are critical for NB's climate. Even an R-18 door loses its advantage if cold air infiltrates around the edges. Quality insulated doors come with compression weatherstripping on the sides and top, and a flexible rubber bottom seal that conforms to minor irregularities in your garage floor. In NB, where frost heave can cause slight slab movement that creates gaps under the door, a dual-contact or bulb-type bottom seal provides the best air seal. Replace weatherstripping every 5 to 7 years, or sooner if you notice daylight or drafts around the door edges.

If you have an existing non-insulated garage door and are not ready to replace it, aftermarket insulation kits are available for $100 to $250 per door. These kits typically use rigid polystyrene or reflective foam panels that friction-fit or adhesive-mount into the door panels. They raise the door's R-value to approximately R-4 to R-8 — a meaningful improvement, though not as effective as a factory-insulated polyurethane door. The added weight of the insulation panels may require a garage door spring adjustment to maintain proper balance, which is a job for a professional — never adjust garage door torsion springs yourself, as they are under extreme tension and can cause serious injury.

For an unheated garage, an R-8 to R-12 door still provides value in NB's Maritime climate by moderating temperature extremes. An insulated door keeps the garage several degrees warmer than outside on cold days, which protects vehicles from extreme cold starts, prevents liquids from freezing, and reduces condensation when temperatures fluctuate during spring and fall freeze-thaw cycles. The insulated door also reduces noise transmission and is more resistant to denting from wind-blown debris and accidental impacts.

Need help choosing and installing the right insulated garage door for your NB home? Browse garage door and general contractors through the New Brunswick Construction Network directory at newbrunswickconstructionnetwork.com.