Duct Sealing & Insulation

Leaky, uninsulated ductwork is the single largest source of energy waste in most GTA homes with forced-air HVAC systems. Studies by NRCan and the US Department of Energy consistently find that typical residential duct systems lose 20 to 30 percent of the conditioned air they carry through leaks at joints, seams, and connections — air that the furnace or air conditioner produced at full energy cost but that never reaches the living space. In a GTA home spending $2,500 to $4,000 annually on heating and cooling, duct leakage represents $500 to $1,200 per year in wasted energy. Sealing and insulating the duct system is one of the highest-return energy upgrades available, often paying for itself within two to three heating seasons. Duct sealing targets every joint, seam, connection, and penetration where conditioned air can escape. Professional sealing uses UL-181 rated mastic sealant — a thick, paste-like adhesive that is applied over joints and reinforced with fibreglass mesh tape — not the metallic "duct tape" that ironically should never be used on ducts. Foil-backed tape rated for HVAC use is acceptable for accessible joints, but mastic is the superior long-term solution because it does not dry out, crack, or release over time the way tape adhesive does. For duct systems with extensive leakage or inaccessible sections — runs buried in walls, between floors, or in tight crawlspaces — Aeroseal technology offers a solution. Aeroseal injects aerosolized sealant particles into the pressurized duct system; the particles accumulate at leak points and build up a seal from the inside, closing gaps up to 5/8 inch without requiring physical access to every joint. Aeroseal is particularly effective in older GTA homes where accessing every duct connection would require opening finished ceilings and walls. Duct insulation addresses the second major energy loss pathway: thermal transfer through duct walls in unconditioned spaces. Ducts running through unheated basements, attics, garages, and crawlspaces lose heat directly through conduction — the warm air inside the duct transfers energy to the cold duct wall, which radiates it into the unconditioned space. R-6 insulation is the minimum for ducts in unconditioned spaces, with R-8 recommended for attic runs where temperature differentials are greatest. In summer, the process reverses — cool air from the air conditioner gains heat as it passes through hot attic ductwork, arriving at registers warm and unable to cool the room effectively. NRCan's EnerGuide program identifies duct insulation as a priority upgrade, and many GTA homeowners pursuing EnerGuide assessments for rebate programs discover that duct sealing and insulation is among the most cost-effective measures on their upgrade list. Total project costs for duct sealing and insulation in GTA homes typically range from $1,500 to $4,000, depending on the size of the duct system, accessibility, and whether Aeroseal technology is used.

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