Ductwork is the hidden infrastructure of your HVAC system. When ducts leak, you're paying to heat and cool your attic, crawlspace, or walls instead of your living areas.
The Scope of the Problem
Average Duct Leakage:
Typical homes lose 20-30% of conditioned air through duct leaks
Some older homes lose 40% or more
That's like throwing away $200-$400 annually
Where Leaks Occur:
Connections between duct sections
Boots connecting ducts to registers
Joints where ducts meet equipment
Holes and tears in duct material
Signs of Duct Problems
Energy Waste:
Higher than expected energy bills
System runs constantly
Temperature hard to maintain
Comfort Issues:
Hot/cold rooms
Uneven temperatures
Musty or dusty smells
Air Quality:
Excessive dust in home
Allergy symptoms worsen
Odors from unconditioned spaces
Duct Sealing Methods
Mastic Sealant:
Thick, paste-like material
Applied to accessible joints
Durable and long-lasting
Professional or DIY application
Foil-Faced Tape:
UL-listed HVAC tape only
Not standard "duct tape" (which fails quickly)
Good for straight seams
Less durable than mastic
Aeroseal:
Seals from inside the ducts
Polymer particles seal leaks
Reaches inaccessible areas
Professional application only
Most thorough option
Benefits of Sealing
Energy Savings:
20-30% reduction in heating/cooling costs
Payback typically 2-4 years
Continues saving for decades
Improved Comfort:
More even temperatures
Better humidity control
Rooms that wouldn't condition now do
Better Air Quality:
Less dust infiltration
Fewer allergens
Reduced outdoor air entry
Equipment Protection:
System runs less
Reduced wear and tear
Potential longer life
Cost Considerations
DIY Mastic Sealing:
Materials: $50-$100
Time: 4-8 hours
Requires accessible ducts
Professional Sealing:
Mastic/tape: $300-$800
Aeroseal: $1,500-$3,000
More thorough results
Bay Area Recommendations
Many Bay Area homes have:
Ducts in unconditioned attics (extreme temperature difference)
Older flex duct that's deteriorated
Multiple renovations with poorly connected additions
Duct sealing is particularly valuable here. Our moderate climate means even small improvements are noticeable.
For best results, combine duct sealing with insulation improvements for maximum energy savings.