You can have the best AC in the world, if your ducts leak, you're paying to cool your attic.
The average home in our service area leaks 20–30% of its conditioned air into the attic through duct joints, plenum gaps, and boot connections. That's a quarter of your electric bill, gone.
How to spot duct problems from your couch
- One room 5°F warmer than the rest
- Dust that reappears the day after cleaning
- AC runs constantly but never quite gets there
- Attic feels unusually cool in summer (that's your cold air)
What sealing actually looks like
Real duct sealing means mastic (a paintable rubber compound) or Aeroseal, not foil tape. Foil tape dries out in a Florida attic within two summers. Mastic outlives the ductwork.
When to seal vs. replace
If ducts are metal or hard board and mostly intact, seal them. If they're flex duct that's older than 15 years, crushed, or disconnected at multiple boots, replacement usually pays for itself faster than repeated seal jobs.
Get it tested
A duct blaster test measures leakage in CFM at 25 pascals. Any HVAC contractor worth hiring will do one before quoting a new system, because installing new equipment on bad ducts is throwing money into the attic.
Sunshine State Heating & Air technical team
Florida state certified HVAC contractor, license CAC1817890 · Google Guaranteed · serving Flagler, Volusia and St. Johns counties since 2014
Our guides are written and reviewed by the licensed technicians who run our service calls out of Bunnell, Florida. Family owned and operated since 2014, we work on residential systems across Flagler, Volusia and St. Johns counties every day, and everything published here reflects what we actually find in the field.
Published April 12, 2026 · Reviewed by our licensed team on March 19, 2026