Range Hood and Ventilation

A Hood That Moves Air Out of the House

The most common hood we replace is not broken. It is a thin under-cabinet unit that has been blowing cooking air through a charcoal filter and straight back into the kitchen for twenty years. It hums, it has a light, and it does almost nothing. When a Bellevue kitchen goes from gas to induction, this is the moment to fix it, because the wall is often open for the new circuit anyway.

Why Induction Still Needs Real Ventilation

Taking the flame out of the kitchen removes the combustion byproducts that a gas burner puts into the air. That is a genuine improvement. What it does not remove is everything the food itself gives off. Searing meat, stir frying and even a big pot of pasta release grease particles, smoke and a lot of water vapor.

In a climate with a long closed-window season, that vapor has nowhere to go. It condenses on the coldest surfaces in the room, which tend to be exterior walls, the backs of upper cabinets and the inside of the hood itself. Over several winters that shows up as peeling paint, swollen cabinet edges and a musty cabinet interior. A hood that exhausts to the outside prevents it.

Capture Area Matters More Than Fan Power

Before fan size, look at the shape. A hood can only exhaust what it catches, and cooking plumes rise and spread.

• Width. A wall hood should be at least as wide as the cooktop, and an extra few inches on each side helps. An island hood needs more, because air moves across it from every direction.
• Depth. A shallow hood that covers only the back burners misses most of what rises from the front ones, which is where people actually cook.
• Height. Mounting height is set by the hood manufacturer, commonly somewhere around 24 to 30 inches above the cooking surface for electric and induction. Higher looks cleaner and captures less.

Sizing the Fan

A commonly used starting point for an electric or induction cooktop against a wall is roughly 100 CFM for each foot of cooktop width, so a 30 inch cooktop lands in the 250 to 300 CFM range. Island hoods are sized higher. Heavy wok or searing habits argue for more.

There is a practical ceiling. Residential mechanical codes generally require make-up air once a kitchen exhaust fan is rated above 400 CFM, so that the fan is not pulling air back down a flue or through gaps in a tightly built house. Make-up air means a dedicated, often tempered, supply of outside air that opens when the hood runs. It is a legitimate solution, but it adds real cost. For most induction kitchens, a well shaped hood at or below 400 CFM with a clean duct run does the job without it. We confirm the requirement with the City of Bellevue for your specific project.

The Duct Run

A strong fan on a bad duct is a weak fan. We use smooth rigid metal duct sized to the hood outlet, keep elbows to a minimum, avoid flexible foil duct, and end the run at an exterior wall or roof cap with a backdraft damper so cold air does not pour in when the fan is off. Joints are sealed with foil tape, not cloth tape, and insulated where the duct passes through unheated space so condensation does not run back into the hood.

The route depends on the house. In a single story rambler, the duct often goes straight up through the attic to a roof cap. In a larger two story home from the 1980s or 1990s, a kitchen under a bedroom may need a run along a joist bay to an exterior wall. We trace that route before quoting, because it drives the price more than the hood does.

Condos and Recirculating Hoods

In downtown high-rise condos, building rules frequently prohibit new penetrations through the exterior wall. When venting outside is genuinely not allowed, a recirculating hood with good grease filters and a fresh carbon filter is better than nothing, and we will say so. We will also say what it does not do: it does not remove moisture, so run the bathroom fan or the building ventilation while you cook.

What It Costs

A ducted hood installation in Bellevue, including mounting, wiring, duct, exterior cap and permit, usually runs $1,800 to $5,500. The low end is a wall hood with a short, straight run through an outside wall. The high end is an island hood, a long ceiling run or a roof penetration. Make-up air, when required, is quoted as a separate line.

Call (425) 663-9860 and tell us the width of your cooktop and where the nearest outside wall is. That is enough to start.