Check your ducts for leaks
Annual · typically July
Why it matters
Your ducts are the delivery trucks of your HVAC system, and in most houses a quarter of the cargo falls off the truck.
And one vocabulary note that saves money: actual "duct tape" (the cloth kind) is the one product NOT rated for ducts — its adhesive cooks and lets go in a season or two. Mastic (paintable goop) and UL-181 foil tape are what last.
What skipping it costs
$200–$900
Typical homes leak 20–30% of their conditioned air out of the ducts before it reaches a room. That's not comfort you lose once — it's a tax on every single heating and cooling hour, commonly $200–$900 a year, paid to heat a crawlspace nobody lives in.
Two ways to get it done
Do it yourself
You'll need: Flashlight, Work gloves, Duct mastic (~$15 a tub) or UL-181 foil tape — NOT cloth duct tape.
With the system fan running:
- Follow every accessible run with the back of your hand at each joint, seam, and boot (where duct meets floor/ceiling). You're feeling for jets of air.
- Look for the telltales where you can't feel: dust streaks radiating from a seam, daylight through a joint, insulation blown clean near a connection.
- Seal what you find: mastic brushed over the joint (gloves, it's like peanut butter), or foil tape on clean metal. Reconnect any popped run with a drive cleat or screws first — tape is not structure.
- Squeeze gently along any flex duct — crushed or kinked sections choke rooms at the end of the line.
- While you're down there, make sure every register boot is actually attached to its register.
Two hours and a $15 tub is the whole DIY budget.
Hire it out
$350–$1,500National fair range — local labor moves this number.
Where ducts are buried in walls or a hostile attic, pros earn their keep: hand-sealing what's reachable, then — only if a duct-blaster test says the leakage justifies it — an aerosol seal for the rest. A legitimate job runs $350–$1500 depending on scope, and the invoice should show before/after leakage numbers. No numbers, no deal.
The sequencing is the honesty test: mastic first (cheap, permanent), measurement second, aerosol only for what hands can't reach. Anyone who starts at the expensive end is selling a product, not solving a leak.
Ask the tech
- Are you hand-sealing the accessible runs with mastic before quoting anything fancier?
- Can you measure leakage before and after — a duct blaster number, not a feeling?
- Which runs are actually accessible, and which would mean opening walls?
Red flags you're being upsold
- An aerosol-seal (Aeroseal-style) quote of $2,000–$4,000 before anyone has hand-sealed the accessible joints with a $15 tub of mastic.
- Duct sealing bundled with a duct-cleaning pitch — sealing is usually worth it, routine cleaning usually isn't; a company leading with the clean has the priorities backwards.
- 'Your ducts are why the bedroom is hot' with no measurement. Sometimes true — but make them show a reading, not a shrug.
Second opinion time: Any full duct-replacement quote. Replacement is occasionally right (crushed flex duct, rodent damage) but it's a four-figure decision that deserves two sets of eyes.
The call
DIY the inspection and mastic the joints you can reach — it's messy, satisfying, and pays for itself in one season. Hire it only if your ducts live where you can't.