What kitchen ventilation is required by NB building code?

New Brunswick Building Code requires kitchen ventilation capable of exhausting cooking contaminants, and for best performance and code compliance, a range hood that vents directly to the exterior is the recommended installation. Recirculating range hoods (which filter and return air to the kitchen) are permitted in some situations, but they don't remove moisture — a serious concern in New Brunswick's already-humid Maritime climate.

The NB Building Code, which adopts the National Building Code of Canada with provincial amendments, requires that kitchens have mechanical ventilation. For residential kitchens, this means a range hood or equivalent exhaust fan installed above the cooking surface. The hood should cover the full width of your cooktop or range and be installed 24-30 inches above the cooking surface for standard residential hoods (check your specific model's installation requirements, as some vary). For gas ranges, an externally vented hood is strongly recommended because gas combustion produces carbon monoxide, nitrogen dioxide, and moisture that must be exhausted outside — not recirculated.

Sizing and CFM Requirements

Hood capacity is measured in CFM (cubic feet per minute), and sizing depends on your cooking equipment and kitchen size. For a standard 30-inch residential range, a hood rated at 250-400 CFM is adequate. If you have a 36-inch professional-style range or a gas cooktop with high-BTU burners, you'll need 400-600 CFM or more. The general rule for gas ranges is 1 CFM per 100 BTU of burner output — a 60,000 BTU range needs at least 600 CFM.

When your hood exceeds 300 CFM, NB Building Code requires makeup air — a system that replaces the air being exhausted to prevent negative pressure in the home. This is especially important in modern airtight NB homes and in older homes that have been retrofitted with improved insulation and air sealing. Negative pressure can cause backdrafting of gas appliances, fireplaces, and water heaters, which is a safety hazard. A makeup air damper integrated with the range hood is the most common residential solution, adding $300-$800 to the installation.

Ductwork matters as much as the hood itself. Use rigid metal duct (not flexible vinyl or foil) for fire safety and airflow efficiency. The duct should be as short and straight as possible — every 90-degree elbow reduces effective CFM by approximately 25%. Vent through an exterior wall or roof cap with a dampered termination to prevent cold NB winter air from blowing back in. During New Brunswick winters, cold air infiltration through a poorly sealed vent cap is a common complaint — install a quality backdraft damper at the hood connection and at the exterior cap.

Permit requirements vary by scope. If you're replacing a range hood on an existing duct run with the same electrical connection, most NB municipalities don't require a permit. However, if you're running new ductwork through walls, adding a new electrical circuit for the hood, or installing a makeup air system, you'll need building and potentially electrical permits. In cities like Moncton, Fredericton, and Saint John, contact your municipal building inspection department. In rural areas, your Regional Service Commission (RSC) handles inspections — expect slightly longer processing times.

Budget $200-$600 for a quality residential range hood, $300-$800 for ductwork installation, and $500-$1,500 for electrical if a new circuit is needed. Professional installation is recommended for ducted hoods to ensure proper sealing, fire safety at wall penetrations, and code-compliant termination. In NB's climate, proper kitchen ventilation is not optional — it protects your cabinets, walls, and air quality from the moisture and grease that cooking generates daily.

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