A range hood that will not clear steam and a dryer that takes three cycles are the same fault in two appliances: the duct, not the motor. Test it by measuring what happens with the duct disconnected — strong airflow at the appliance with weak airflow at the outside wall means the run is restricted, crushed, too long, or terminating at a flap that no longer opens. Duct work is cheap; motors are not.
Read this first
- Lint in a dryer duct is fuel. Clearing the run is a fire-prevention job, not a performance tweak.
- Never run a dryer that vents into the room or into a crawlspace. It dumps moisture and, on a gas dryer, combustion products into the house.
- Never run a range hood with the grease filters removed. The filters are the only thing keeping grease out of the blower and the duct.
- Cut the breaker before opening a hood housing — most are hardwired — and never degrease a hood that is still hot.
What it usually means
Ducted appliances live or die on static pressure. Every elbow, every foot of flexible foil, and every partly closed damper adds resistance, and manufacturers publish a maximum equivalent length for exactly that reason. Most underperforming installations are not faulty at all — they are simply asking a blower rated for a short straight run to push through forty feet with five bends and a screened cap full of lint.
The two appliances fail differently at the end of the duct. A hood coated in grease loses airflow gradually and eventually starts dripping, which is a fire load rather than a nuisance. A dryer with a restricted vent runs hot, trips its thermal fuse, and — because lint is the fuel — is the appliance most often named in household fire statistics. In both cases the duct is the repair, and the motor is usually innocent.
What to check first
Disconnect at the appliance and feel the airflow
With the duct off, a dryer should push a strong warm stream and a hood should pull a sheet of paper firmly against the filters. Good airflow at the appliance and poor airflow outside is conclusive: the run is the problem.
Go outside and watch the flap
Run the appliance and look at the exterior cap. The damper should swing fully open. Lint-packed flaps, painted-shut louvres and bird screens clogged solid are extremely common and completely invisible from inside.
Replace flexible foil with rigid metal
Concertina foil duct behind a dryer is the single worst thing in most laundry rooms — it traps lint in every corrugation and crushes flat when the machine is pushed back. Rigid or semi-rigid metal, with a straight run and foil-taped joints, transforms performance.
Wash the hood filters and degrease the blower
Hold each filter to a light — you should see through it. Soak in hot water with degreaser, and with the breaker off, degrease the blower wheel and housing too. Grease on the wheel unbalances it and kills the airflow the fan was rated for.
Count the elbows and measure the run
Each 90-degree bend costs the equivalent of several feet of straight duct. A run that exceeds what the manufacturer specifies will underperform forever, no matter how new the motor is. Shortening it or removing one bend often solves the whole complaint.
Check for makeup air on a powerful hood
A high-CFM hood in a well-sealed house can be trying to exhaust more air than can leak back in. If it works noticeably better with a window cracked, the problem is makeup air rather than the hood.
DIY, technician, or licensed trade?
This is about who is allowed to do the work, not how hard it is. The bottom row is not a difficulty rating — it is the legal and safety line, and it does not move for confidence or experience.
- Clearing a dryer duct run and the exterior flap
- Replacing foil duct with rigid or semi-rigid metal and foil-taping the joints
- Washing hood grease filters and emptying the grease cup
- Degreasing the blower wheel and housing with the breaker off
- Replacing a hood blower motor, wheel or speed control
- Professional dryer vent cleaning on a long or inaccessible run
- Replacing a dryer cycling thermostat or moisture sensor once the vent is proven clear
- Rerouting, resizing or insulating a duct inside a wall, ceiling or attic
- Fitting a makeup air system, which is code-driven in many jurisdictions
- Any hardwired connection at a hood or a dryer circuit
Likely parts and what they cost
Our estimates for a typical US job, not quotes. “Part only” is what the component costs bought online against a model number; “installed” adds a technician’s diagnostic and labor.
| Part | Part only | Installed | Notes |
|---|---|---|---|
| Rigid metal duct kit and foil tape | $20–$60 | $100–$300 | The highest-value repair on this page by a wide margin. |
| Exterior vent hood or cap | $15–$50 | $120–$280 | Choose a design without a bird screen for a dryer — screens pack solid with lint. |
| Range hood grease filters | $15–$65 | n/a — DIY | Wash monthly; replace when the mesh is crushed or the baffle is deformed. |
| Hood blower motor or wheel | $45–$160 | $150–$450 | Confirm the duct is clear first, or the new motor performs the same. |
| Professional vent cleaning | n/a — service | $100–$350 | Worth it annually on a long run, and the safest option on a roof termination. |
Prices are general estimates for typical US jobs, not quotes. What you actually pay depends on your appliance's brand and age, the part required, your region, and each shop's labour rate. Get the model number off the appliance before ordering — the same part varies in price across models.
Step-by-step guides for this symptom
4 guides cover this fault across 2 appliance types. Each one works through it in diagnostic order, with tools, parts and the point at which it stops being a DIY job.
- 45–120 minutesRange Hood
Range Hood Fan Weak or Not Venting — Restore Airflow
Hood running but smoke still fills the kitchen? Degrease the filters, check the damper, clean the blower wheel and check the duct run with this DIY guide.
- 45–120 minutesRange Hood
Range Hood Loud or Rattling — Quiet It Down
Rattle, buzz, whine or a roar out of proportion to the airflow. Clean the blower wheel, secure the filters and ducting, and check the motor bearings.
- 60–150 minutesRange Hood
Range Hood Dripping Grease — Fix the Cause, Not the Drip
Grease running down the hood or dripping onto the cooktop means saturated filters or condensate in the duct. Clean the system properly and stop the cause.
- 45–120 minutesDryer
Dryer Takes Too Long — Restore Full Drying Speed
A dryer that needs two or three cycles is almost always an airflow problem. Clean the vent, test the lint screen, check the blower and moisture sensor bars.