Every time the system kicks on you get whistling, howling, or a moan from the vents or ductwork.
You probably came here because…
- Whistling from a specific vent or return grille
- Howling sound from ductwork in the attic or basement
- Noise starts the moment the blower kicks on
- Noise may change pitch as the system ramps up
What’s actually happening
Whistling ducts are air moving through a gap too small for the volume. Two causes: static pressure is too high (system is trying to move more air than the ducts can handle) or there's a leak at a joint or seam where high-pressure air is escaping.
High static pressure comes from the same problems as weak return airflow: too-restrictive filter, undersized ducts, closed dampers, or too-few returns. Except now the sound is telling you.
Leaks at joints are usually where flex duct meets a boot or trunk, or where sheet-metal takeoffs seal to plenums. Mastic sealant or good foil tape fixes them fast.
What we do about it
Isolate the noise
Which vent is whistling? Or is it the ductwork itself? Stand near each vent with the system running to pinpoint the source before you go looking for the problem.
Check for closed dampers
If someone closed a damper or a supply register to force air elsewhere, the pressure in the rest of the system spikes and you get whistling at the still-open vents. Open everything back up as a test.
Look for visible leaks
In the attic or basement, run the system and feel around duct joints and takeoffs. A leak is obvious – you'll feel a jet of air. Fix with mastic or good foil tape (never the cloth kind – it fails).
When to just call
If the system is properly ducted and it's still whistling, static pressure needs to be measured. High static pressure will kill your blower motor. Call (423) 637-1846 – we can measure it in 15 minutes and tell you what's fixable.
Ready to fix it?
Call the family that’s been doing this in the Sequatchie Valley since 1996.