Range Hood and Ventilation

Getting the Smoke Out Before It Reaches the Living Room

A range hood has one job. It has to catch the rising plume of heat, steam, grease and smoke coming off the cooktop and move it outside before it drifts into the rest of the house. Almost every hood we replace in Carlsbad was failing at the first half of that job, the catching, long before the fan motor wore out.

When a kitchen is a closed room, a weak hood is an annoyance. When the kitchen opens onto a family room and the island is where guests stand with a drink, the same hood means the whole downstairs smells like salmon for two days and someone waves a dish towel at the smoke detector.

Capture Area Comes First

Smoke does not rise in a neat column. It spreads as it climbs, and it gets pushed sideways by anyone walking past or by a breeze through an open slider. A hood catches that plume only when it is wide enough and low enough.

For a wall hood, we like the hood to be at least as wide as the cooktop, and a few inches wider on each side when the cooking is heavy. A thirty six inch range under a thirty six inch hood works. The same range under a thirty inch hood lets the outer burners escape. Depth matters too: a shallow hood misses the front burners, which are the ones people actually use.

Mounting height follows the hood manufacturer’s installation instructions, which typically fall somewhere between 24 and 36 inches above the cooking surface depending on the fuel and the model. Every inch higher widens the plume the hood has to catch. Tall homeowners sometimes ask us to raise a hood so they do not bump their heads, and we will talk through that trade honestly, because it costs capture.

Island Hoods Need More

An island cooktop has no back wall to steer the plume upward, and air moves across it from every side. Island hoods need more overhang past the cooktop and noticeably more airflow than the same cooktop against a wall. They also need a duct path through the ceiling, which means looking at joist direction, what is in the floor above, and whether the attic or a soffit chase can carry the duct to the roof.

Airflow Without the Marketing

Hood fans are sold on CFM, cubic feet per minute. Bigger numbers look better on the box, and they are the least useful number in the conversation if the capture area and duct are wrong.

As a starting point, a wall hood over an electric or induction cooktop does well at roughly 100 CFM per foot of cooktop width, and an island hood closer to 150. A gas range is usually sized from its total burner output, commonly 100 CFM for every 10,000 BTU. From there we adjust for what you cook. Someone who sears steaks and runs a wok on high heat for guests needs more than someone who mostly simmers.

The Duct Decides What You Get

A fan rated at 600 CFM on a six inch duct with three elbows and a long run might move half that. It will also be loud, because it is straining against resistance. We size the duct to the fan, use smooth rigid metal rather than flexible foil, keep the run as short and straight as the framing allows, and seal every joint with foil tape rather than cloth duct tape, which dries out and falls off in an attic.

Loudness is its own issue in an entertaining kitchen. A hood rated in sones at high speed that drowns out conversation will get turned off. Remote and inline blowers, mounted in the attic or at the roof, move the noise away from the room.

Make-Up Air

Every cubic foot a hood pulls out of the house has to be replaced from somewhere. In an older Olde Carlsbad cottage with gaps around the windows, it leaks in on its own. In a newer, tightly built home in Bressi Ranch or Robertson Ranch, a strong hood may pull air backward down a fireplace flue or a gas water heater vent, or simply not move the air it is rated for.

Many residential codes call for a make-up air system once a kitchen exhaust fan passes 400 CFM. We confirm what applies to your house during plan review with the City of Carlsbad, and we design the make-up air path, often a motorized damper interlocked with the hood, before a large blower is ordered.

Coastal Conditions

West of the freeway, salt air and the morning marine layer corrode cheap exterior caps and backdraft dampers. A stuck-open damper lets cold damp air and the occasional bird into the duct. We specify caps and dampers built for the coast and place wall caps where they can be reached for cleaning. In planned communities in La Costa, Aviara and Rancho Carrillo, a new roof or wall penetration on a visible elevation may need HOA approval, and we prepare that submission with the permit set.

When We Tell You Not to Spend

If your existing duct already runs outside at a sensible size, a good hood swap may be all you need. If you rarely cook at high heat, a modest hood on a clean run beats a showpiece. We would rather say that on the walkthrough than install something oversized.

Call (442) 315-0648 to have us look at your ceiling and your cooktop.