How do I air seal a garage to prevent drafts without creating moisture problems in NB?

Air sealing a garage in New Brunswick requires a balanced approach that stops drafts while maintaining enough ventilation to prevent moisture buildup from vehicles, temperature changes, and Maritime humidity.

The key to successful garage air sealing in NB is understanding that you're not creating a completely airtight space like a house — you're reducing unwanted air infiltration while preserving intentional ventilation. This is especially critical in our Maritime climate where bringing a snow-covered vehicle into a warmer garage creates significant moisture release that must be managed.

Start with the major air leakage points that cause the most comfort and energy loss. The garage door itself is typically the largest source of air infiltration. Install new bottom weatherstripping if the existing seal is cracked or compressed — this rubber or vinyl seal should compress against the floor when the door is closed but not bind during operation. Side and top weatherstripping around the door frame prevents air infiltration around the perimeter. For overhead doors, check that all sections seal properly against each other — worn hinges or bent door sections create gaps that let in cold air and moisture.

The service door (man door) between the garage and exterior needs proper weatherstripping around the entire frame, plus a door sweep at the bottom. If this door leads to the house, it requires more attention since it affects your home's overall air tightness. Any windows in the garage should be caulked around the frame and have functional weatherstripping if they're operable.

Address structural air leaks that are often overlooked but significant in NB's temperature extremes. Seal the gap between the bottom plate (sill plate) and the concrete foundation with acoustical sealant or expanding foam — this connection is rarely perfect and allows ground-level cold air infiltration. Caulk around any electrical outlets, light fixtures, or other penetrations through the exterior walls. If your garage has a ceiling (rather than open rafters), seal around any ceiling penetrations like lights or garage door opener wiring.

For attached garages, air sealing the fire separation wall serves dual purposes — it's required by code for fire safety and dramatically improves comfort in adjacent living spaces. All electrical boxes, plumbing penetrations, and HVAC ducts that pass through this wall must be sealed with appropriate fire-rated materials. The gap at the top and bottom of the drywall should be sealed with acoustical sealant before installing trim.

The critical balance is maintaining adequate ventilation while reducing unwanted air leakage. Even a well-sealed garage needs air exchange to prevent moisture problems, especially if you park vehicles inside during winter. When a vehicle covered in snow and road salt enters a garage that's 10-20 degrees warmer than outside, the rapid temperature change releases significant moisture. Without ventilation, this moisture condenses on tools, stored items, and the walls themselves.

Install intentional ventilation rather than relying on random air leaks. A simple solution is a through-wall exhaust fan on a timer or humidity sensor — run it for 15-30 minutes after parking a wet vehicle to remove moisture-laden air. Passive ventilation can work too: install soffit vents near the floor on one wall and ridge or gable vents high on the opposite wall to create natural air circulation. The key is controlling where air enters and exits rather than having random leakage throughout the structure.

For heated garages, the ventilation requirement increases because the temperature differential creates more condensation potential. A heated garage should have at least 0.5 air changes per hour, either through mechanical ventilation or a combination of controlled passive vents. Never seal a heated garage completely tight — the moisture problems will be severe and expensive to remediate.

Avoid common air sealing mistakes that create problems in NB's climate. Don't seal the garage so tightly that vehicle exhaust has nowhere to go — carbon monoxide buildup is dangerous and potentially fatal. Don't ignore the need for combustion air if you have a gas-fired heater or hot water tank in the garage. Don't use expanding foam around the garage door tracks or springs — this can interfere with door operation and create binding.

When to hire a professional: Basic weatherstripping and caulking are good DIY projects, but if your garage has complex air leakage issues, moisture problems, or you're planning to add heating, consult with an insulation contractor or energy auditor who understands Maritime climate conditions. They can perform a blower door test to identify major leakage points and recommend the right balance of air sealing and ventilation for your specific situation.

The goal is a garage that's comfortable to work in, protects your vehicles and stored items, but doesn't trap moisture that leads to rust, mould, and deterioration in NB's humid climate.