Filed
The complaint is almost always the same. The hood runs, the lights work, it is noisy enough to be doing something, and the kitchen still fills with smoke whenever the rangetop is used properly.
The blower is usually innocent.
What the local housing stock forces
The subdivisions on this side of the river — Oakleaf Plantation, the Argyle Forest corridor, most of what has gone up around Orange Park in the last few decades — are built slab-on-grade under truss attics. There is no basement to run duct through and, in most plans, no vertical chase behind the kitchen wall.
So the duct goes up into the attic and then sideways, sometimes a long way, to a roof or gable termination. Every one of those horizontal feet costs a little airflow, and every elbow costs the equivalent of several more feet on top.
A hood rated for a certain airflow on a test bench is not delivering that number at the end of a long attic run with four elbows in it. That is not a defect. It is arithmetic, and it should have been accounted for at installation.
The three things that go wrong up there
Flexible duct where rigid metal belongs. Flex turns corners easily, which is exactly why installers reach for it, and its corrugated inner wall is substantially more resistive than smooth pipe. Worse, an unsupported flex run sags between trusses and every low point becomes a grease trap. Eventually the sag holds enough to restrict flow on its own.
A termination cap that no longer opens. Roof and gable caps have a damper, and dampers gum up with grease and insect nesting. The blower then works against a closed door. From the kitchen this is indistinguishable from a weak motor.
No insulation on the duct. A Florida attic in August is brutal, and an uninsulated metal duct running through it condenses on the inside when the hood pushes warm humid kitchen air into it. The water runs back down the slope toward the hood, drips onto the cooktop, and gets reported as a leaking appliance.
Sizing and height come first anyway
Before the attic is even discussed, three measurements settle most capture complaints.
The hood should be at least as wide as the cooking surface — wider is better on an island, where there is nothing to stop the plume drifting. The mounting height has to be within the range the manufacturer specifies for that model; a hood raised to keep sight lines clean loses the front burners permanently. And the canopy depth has to cover the front burner row, not just the back one.
A hood that fails these is not repairable by parts. Saying so on the first visit is more useful than replacing a blower that was working.
Make-up air
Newer houses here are built tight. A powerful blower needs its replacement air from somewhere, and if no path is provided it finds one backwards through whatever is easiest — which can include a water heater or an air handler return.
The tells are worth knowing: a door that resists opening while the hood runs, a whistling around window frames, or a back-draft smell when the air handler cycles at the same time as the hood.
Which is the point at which this note has to name its own boundary. The air handler, the return it is starved by and every foot of duct that heats or cools the house belong to an HVAC contractor. This bench works on Wolf cooking equipment and kitchen ventilation; a make-up air path is identified, written down and handed on, not quoted.
Two things that cost nothing
Wash baffle filters by hand and let them dry flat. A filter that came out of a dishwasher slightly warped will rattle at high speed and lose seal at the edges, and both get blamed on the motor.
Then pull the blower wheel and look at it. Ten years of grease loading on one side of a wheel is enough to put it out of balance, and the rumble that produces is the single most common reason a healthy motor gets replaced.