What R-value garage door should I choose for Maritime winters in NB?

For a garage that you plan to heat or insulate in New Brunswick, choose a garage door with a minimum R-value of R-16, and ideally R-18 or higher. If your garage is unheated and used strictly for vehicle storage, a lower R-value of R-8 to R-12 can work, but given NB's six-month heating season and temperatures that regularly drop to -20 to -30 degrees Celsius, investing in a well-insulated door pays for itself in comfort and energy savings within a few years.

The R-value of a garage door measures its resistance to heat flow — the higher the number, the better the door prevents heat from escaping in winter and entering in summer. In New Brunswick's Maritime climate, where communities accumulate 4,800 to 5,200 heating degree days per year, the garage door is by far the largest single opening in the building envelope. A standard two-car door at 16 by 7 feet represents over 112 square feet of surface area, and if that door is poorly insulated, it functions essentially as a giant cold wall radiating frigid air into your garage all winter long. Even if you have insulated the walls and ceiling to R-20 and R-32 respectively, a non-insulated garage door undermines the entire thermal envelope.

Polyurethane-injected doors offer the best R-value per inch of thickness and are the preferred choice for NB garages. These doors have a continuous layer of polyurethane foam injected between the steel skins during manufacturing, which eliminates air gaps and provides both insulation and structural rigidity. A typical 2-inch-thick polyurethane-injected door delivers R-16 to R-18, while a 3-inch door can reach R-20 or higher. By contrast, polystyrene-inserted doors — where pre-cut foam panels are placed between the skins — typically deliver R-8 to R-12 and have small air gaps around the panel edges that reduce real-world performance.

For heated workshops, home gyms, or garages attached to your house, R-16 or higher is the right investment. The price difference between an R-8 and an R-16 single garage door in New Brunswick is typically $300 to $600, while the difference for a double door is $500 to $900. When you consider that heating a poorly insulated garage through an NB winter can cost $800 to $1,500 or more in propane or electricity, the upgraded door often pays for itself in two to three heating seasons. An insulated door also runs more quietly, resists denting better than a single-skin door, and reduces condensation on the interior surface — a real advantage in NB's high-humidity Maritime climate where cold surfaces attract moisture.

Don't forget the weatherstripping and bottom seal. Even the highest R-value door loses its effectiveness if cold air pours in around the edges. Make sure your door includes a thermally broken bottom seal (vinyl or rubber, not bare aluminum), perimeter weatherstripping on the jambs and header, and a proper threshold seal if your slab is uneven. In NB, these seals take a beating from road salt, freeze-thaw cycles, and UV exposure, so inspect and replace them every two to three years to maintain the door's insulating performance.

If you are building a new garage or replacing an existing door, a professional installer can help you select the right R-value for your specific situation — whether you are heating the space, how the garage connects to your home, and what your budget allows. Need help finding a professional garage door installer? New Brunswick Garages can match you with local contractors for free through the New Brunswick Construction Network.