Range Hood Dripping Water? Condensation Causes and Fixes

Water dripping from a range hood is almost always one of two things: condensation from cooking steam hitting a cold duct, or rain getting in through the exterior cap. The fastest way to tell them apart is timing. If it drips while you cook, especially in winter, it is condensation. If it drips during or after rain, look outside.

If the drips are brown and sticky rather than clear, you are probably dealing with grease instead. See grease dripping from a range hood for that problem.

Quick diagnosis

Why condensation happens in range hood ducts

Cooking puts a lot of water into the air. A big pot at a rolling boil releases steam steadily, and that warm, wet air rises into the hood and up the duct. When the duct passes through a cold attic, garage or exterior wall, the metal can be far below the air’s dew point, so water forms on the inside walls the same way it beads on a cold glass.

When a duct runs level or sags back toward the hood, or runs straight up through the roof, that water flows back down and drips out of the hood collar, the filters or the light housing.

Cause 1: Fan speed too low for the steam load

This is the cheapest thing to fix and the most common trigger. On low speed, moist air moves slowly, spends more time in contact with the cold duct and has more time to condense.

How to check

1. Put a large pot of water on to boil with the fan on low.
2. After 10 minutes, look for drips at the filters or collar.
3. Repeat on a different day with the fan on medium or high.

If drips mostly disappear at higher speed, airflow is part of the problem.

How to fix

1. Turn the fan on before the water starts steaming, not after the kitchen is already humid.
2. Use medium or high speed whenever you boil, steam or simmer uncovered.
3. Keep the fan running 10–15 minutes after cooking to push the remaining moisture out and let the duct warm up and dry.
4. Use lids when you can. A covered pot releases far less steam.

If the fan seems weak even on high, fix that first with range hood not venting / weak suction. A hood that is undersized for your cooktop will struggle with steam; the CFM calculator will tell you what size you should have.

Cause 2: Uninsulated duct in unconditioned space

If the duct runs through an attic, a garage or an exterior wall, it will be cold in winter. This is the most common root cause of persistent condensation.

How to check

1. Figure out the duct route. Follow it from the hood toward the wall or roof cap.
2. If it goes through an attic, go up with a flashlight and a stable ladder. Look for bare metal duct, especially the elbows and any section near the roof.
3. On a cold day, run the fan on high for 5 minutes while boiling water, then touch the duct in the attic carefully. A duct that feels cold and wet on the outside or has water stains on the surrounding framing is a clear sign.
4. Check the joints. Gaps let moist air leak into the attic, where it can cause mold on sheathing.

How to fix

1. Seal every joint and seam with foil HVAC tape. Do not use cloth duct tape; it dries out and falls off.
2. Wrap the duct in foil-faced duct insulation, about R-6 or better, covering the full length that passes through cold space. Tape the seams of the insulation so the vapor barrier is continuous.
3. Confirm the duct is rigid galvanized or stainless steel. Flexible foil duct traps water and grease in its ridges; replace it. The IRC 2021 (M1503.4) requires galvanized steel, stainless steel or copper for kitchen exhaust ducts.
4. Confirm the duct actually ends outdoors at a cap. The IRC (M1503.3) does not allow kitchen exhaust to discharge into an attic or crawl space. A duct that dead-ends in the attic will soak the insulation and framing.
5. If possible, shorten the run. Every 90° elbow costs roughly as much as 10–15 feet of straight duct, and a longer, slower path gives steam more time to condense. Aim for under 30 equivalent feet.

Working in an attic means ladders, joists and possibly exposed wiring. Step only on framing, and bring someone to hold the ladder.

Cause 3: Missing or stuck backdraft damper

A backdraft damper closes when the fan is off. Without one, cold outdoor air sinks into the duct and chills it, and warm kitchen air can drift up and condense even when you are not cooking.

How to check

1. With the fan off on a cold day, hold your hand under the hood. A steady cold draft means the damper is missing or stuck open.
2. Look up into the hood collar with a flashlight. You should see a flap that moves freely when you push it with a finger.
3. Check the wall or roof cap outside for a flap that opens when the fan runs and closes when it stops.

How to fix

1. Clean any grease holding the flap open with warm water and degreasing dish soap.
2. If there is no damper at the collar, add an in-line backdraft damper sized to your duct.
3. If the exterior flap is stuck, see exterior vent flap stuck or not opening.

Cause 4: Rain getting in through the wall or roof cap

If the drips line up with rain rather than cooking, the water is coming from outside.

How to check

1. Note whether drips appear during wind-driven rain, only from one direction, or after snow melts on the roof.
2. Inspect the cap from the ground with binoculars or, if it is safe, from a ladder. Look for a missing hood, a broken flap, cracked sealant or lifted shingles and flashing around a roof jack.
3. Check that a wall cap is angled slightly downward and outward so water drains away from the house.

How to fix

1. Reseal gaps around a wall cap with exterior-grade sealant at the top and sides; leave the bottom edge open so any water that gets behind it can drain.
2. Replace a cracked or flapless cap with a proper kitchen exhaust cap that has a built-in damper and is sized to match your duct. Avoid screened dryer-style caps; grease clogs fine screens.
3. Roof jacks with failed flashing are a roofing job. Unless you are comfortable on a roof, call a roofer. Do not climb onto a wet or steep roof.

Cause 5: Frost at the outlet in very cold weather

In deep cold, moist exhaust can freeze at the cap, narrowing the opening. When it melts, the water runs back in.

How to check

On a cold morning, look at the cap for frost or ice buildup, especially after a long simmer the night before.

How to fix

1. Insulate the duct all the way to the cap so the air stays warmer until it exits.
2. Run the fan on higher speed for steamy cooking so moisture leaves faster.
3. Clear ice gently from the cap by hand from a safe position; do not chip at it with tools that can crack plastic caps.

Protect the hood while you fix it

Water near the hood’s light sockets, controls or motor is a problem. If you see drips near the light or control panel, or the hood starts flickering or acting erratically, turn off power at the breaker, not only at the hood’s switch, until the source is fixed. Dry the hood interior with a towel, and wash the filters because water often carries grease with it; see how to clean range hood filters.

Long-term moisture can also rust the inside of a duct and loosen grease deposits. If your duct has been wet for years, read grease buildup in ductwork before your next deep clean.

When to call a pro

Call a professional if:

• The duct runs through a space you cannot safely reach, such as a closed ceiling cavity or a steep roof.
• The roof flashing or wall siding around the cap is damaged or leaking into the wall.
• You find water stains, soft drywall or mold around the duct route; the leak has likely been going on for a while.
• Water has reached the hood’s wiring, controls or motor, and the hood now behaves oddly.
• The duct turns out to vent into the attic or uses flexible foil duct, and it needs to be rerouted. An HVAC contractor or experienced handyman can reroute it; check with your local building department about permits.

The short version

Clear water from a range hood while you cook is condensation. Run the fan higher and longer, insulate any duct in cold space, and make sure a working damper closes the duct when the fan is off. If it only drips when it rains, the cap or flashing is the problem, and that fix happens outside.