What range hood CFM rating do I need for my NB kitchen?

For most New Brunswick kitchens with a standard 30-inch residential range, you need a range hood rated at a minimum of 300 to 400 CFM (cubic feet per minute), but if you have a gas range or do heavy cooking like stir-frying or deep-frying, aim for 600 CFM or higher. Proper ventilation is especially critical in NB's humid Maritime climate, where excess cooking moisture promotes mold growth behind cabinets and in wall cavities.

The general rule for sizing a range hood is straightforward. For electric ranges, calculate 1 CFM per 10 BTU of burner output, or simply use 100 CFM per linear foot of range width — so a 30-inch range needs at least 300 CFM, and a 36-inch range needs at least 360 CFM. For gas ranges, the calculation is based on the total BTU output of all burners combined. A typical residential gas range produces 40,000 to 60,000 BTU total, requiring 400 to 600 CFM. High-output professional-style gas ranges producing 80,000+ BTU need 800 to 1,200 CFM hoods.

However, CFM ratings on the box do not tell the whole story. Duct run length and configuration dramatically affect actual airflow. Every foot of ductwork and every 90-degree elbow reduces effective CFM. A hood rated at 600 CFM with a short, straight 6-inch duct to the exterior wall might only deliver 400 CFM through a long duct run with two elbows going up through the attic. In many older NB homes where kitchens are on interior walls, the duct run to an exterior exit can be quite long, so sizing up by 100 to 200 CFM compensates for this loss.

Venting to the Exterior is Non-Negotiable

In New Brunswick, your range hood must vent to the outside — recirculating hoods are not adequate for this climate. Recirculating hoods push grease-filtered air back into the kitchen but do nothing to remove moisture, combustion gases (from gas ranges), or odours. In NB's already-humid summer months, adding cooking moisture to indoor air creates ideal conditions for mold behind kitchen cabinets, under sinks, and inside wall cavities. A properly ducted range hood removes both moisture and contaminants entirely from the home.

For ductwork, use smooth rigid metal ducting (6-inch diameter minimum, 8-inch for hoods above 600 CFM) rather than flexible aluminum ducting, which restricts airflow and collects grease. The duct should exit through an exterior wall or roof cap with a backdraft damper to prevent cold NB winter air from flowing back in when the hood is off.

Noise is a practical consideration. Higher-CFM hoods are louder. Look for hoods rated in sones — under 3 sones at normal speed is comfortable for conversation, while anything above 6 sones becomes disruptive. Many quality hoods offer variable speed so you can run quietly for everyday cooking and boost to full power for heavy frying.

Range hoods in the 300 to 600 CFM range cost $200 to $800 for chimney-style models and $400 to $1,500 for under-cabinet or insert models. Professional-grade hoods (900+ CFM) run $1,000 to $3,000. Installation with new ductwork typically costs $300 to $800 in New Brunswick, depending on duct run complexity. If you are cutting a new exterior wall penetration, your contractor will need to account for vapour barrier sealing around the duct cap — critical in NB to prevent moisture infiltration.

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• Gionetterenovations
• Thirty Four Renovations