· Michael Blair
Most range hoods in existing Nashville kitchens do not vent outside. They pull air through a filter and blow it back into the room, which handles some grease and odour and does nothing at all about heat or moisture. In a climate where indoor humidity is already the problem, that distinction matters.
What a recirculating hood does and does not do
A charcoal filter absorbs some odour and a mesh filter catches grease. Everything else, including the water vapour from boiling, the combustion products from a gas burner and most of the heat, goes straight back into the kitchen.
Cooking is one of the larger moisture sources in a house. In Middle Tennessee, where summer indoor humidity is already a fight, returning that moisture to the room adds load to the air conditioning and contributes to the clammy feeling at a thermostat setting that should be comfortable.
What a ducted run actually requires
Smooth rigid metal duct, sized to what the hood specifies and not reduced along the way, with as few elbows as the layout allows and a straight run to an exterior wall or through the roof. Flexible foil duct kills the performance of a good hood and traps grease in its ridges.
It has to terminate outside with a damper, not in the attic, not in a soffit and not in the crawl space. Venting a moisture and grease source into an attic is how Nashville houses get mould in the sheathing above the kitchen.
- Rigid metal duct, never flexible foil
- The diameter the hood specifies, not the one that fits
- Minimum elbows, shortest practical route
- Exterior termination with a backdraft damper
- Never terminate into an attic, soffit or crawl space
Makeup air, and why a big hood can misbehave
A powerful hood removes a lot of air, and that air has to be replaced. In a reasonably tight house a large hood can pull hard enough to depressurise the space, which draws air down any available opening, including a water heater or furnace flue.
That is called backdrafting and it moves combustion products into the house. Codes address it with a makeup air requirement above a certain hood capacity. It is the reason the biggest hood available is not automatically the right one, and the reason a hood upgrade in a house with atmospherically vented gas appliances deserves a conversation.
Getting the size and the placement right
A hood should be at least as wide as the cooking surface and ideally wider, and it should be mounted at the height the manufacturer specifies rather than the height that looks right. Too high and it captures nothing; too low and it is a fire risk over a gas burner.
Capture area matters more than raw fan power. A deep hood that covers the front burners catches the plume as it rises; a shallow decorative hood at the same fan rating lets most of it past. Front burners are where most cooking happens and the hardest place to capture from.