Range Hoods in Airtight Homes

If you live in a house or building, chances are you have a range hood in your kitchen over your cooktop. A range hood contains a mechanical fan that, when turned on, helps to extract airborne grease, combustion products, fumes, smoke, heat, and steam from the air by evacuating it to the outside.

In most range hoods, a filtration system removes grease and other particles. Although many vent hoods exhaust air to the outside, some recirculate the air back to the kitchen. In a recirculating system, additional filters may be used to remove odours as well as grease.

Mechanical Ventilation Systems in Kitchens

In high-performance and Passive House homes with mechanical ventilation systems, an extraction point is located in the kitchen area to remove some of the moisture and smells that occur during cooking. Even though this handles a large amount of background ventilation, it won’t remove all the by-products of cooking — so a range hood is also required to work in unison with the mechanical ventilation system.

Make-Up Air for Range Hoods in Airtight Homes

In an airtight or Passive House–standard home, a powerful ducted range hood can cause significant negative pressure when extracting air. Without a source of replacement (make-up) air, this can:

• Reduce the performance of the range hood
• Pull in air through unintended leaks, bypassing the ventilation system
• Affect the operation of other exhaust appliances such as clothes dryers or wood heaters

To prevent these issues, some homes incorporate a dedicated make-up air supply that opens when the range hood is in use. This ensures balanced airflow and maintains the integrity of the ventilation system.

Balancing with MVHR Systems

If your home uses a Mechanical Ventilation with Heat Recovery (MVHR) system, it’s important to note that these units are not designed to cope with large, short-term extraction loads from range hoods. In most cases:

• The MVHR continues to provide background ventilation
• The range hood operates independently, exhausting directly outside
• Backdraft dampers or automated dampers prevent air from re-entering the home through the duct when the hood is off

What About Recirculating Range Hoods?

In some high-performance homes, a recirculating range hood with a high-quality charcoal filter may be used to avoid large penetrations in the building envelope. This can be suitable when:

• Cooking is light and infrequent
• Strong-smelling or high-grease cooking is avoided
• The MVHR system provides adequate extraction in the kitchen zone

Best Practice for Airtight Homes

1. Use a ducted range hood vented outside, with a sealed damper when not in use.
2. Integrate make-up air to prevent negative pressure.
3. Coordinate with your ventilation designer so the system works in harmony with the MVHR.
4. Select a hood that is quiet, efficient, and easy to clean.

By planning early in the design process, you can enjoy the benefits of both a high-performance building envelope and effective kitchen ventilation without compromising comfort or air quality.