Range hoods in airtight homes
A standard ducted range hood and an airtight building envelope work against each other. Here's why — and how to get both right.
The problem with standard range hoods
A range hood works by extracting air from the kitchen — pulling it through the hood, through a duct, and exhausting it outside. In a draughty house, this isn’t an issue: replacement air simply leaks back in through gaps and cracks in the building envelope.
In an airtight home, the same process creates a problem. A powerful ducted range hood extracting 400–900 m³/h can depressurise the building significantly. With no easy path for replacement air, the hood’s extraction performance drops, negative pressure builds up, and air is forced in through whatever leakage paths exist — bypassing your filters, your thermal envelope, and your MVHR system entirely.
In homes with wood heaters, gas appliances or clothes dryers, significant negative pressure also creates a risk of backdraught — combustion gases or exhaust air being drawn back into the living space rather than exhausted outside.
The short version
Every litre of air a range hood extracts must be replaced from somewhere. In an airtight home, you need to design where that replacement air comes from — or accept that your building envelope is working against your ventilation system.
Option 1 — Ducted range hood with make-up air
The most effective solution for high-performance homes is a conventional ducted range hood paired with a dedicated make-up air supply. When the range hood activates, a controlled supply of fresh air enters the building — either through an automated damper in the duct system, or via a supply grille near the cooktop — replacing exactly the volume of air being extracted.
This keeps the building at neutral pressure, preserves MVHR performance, and allows the range hood to operate at full extraction capacity. The make-up air damper is typically interlocked with the range hood so it only opens when the hood is running.
- Full extraction performance — no compromise on cooking odours or steam
- Building remains at neutral pressure during hood operation
- MVHR continues to operate normally
- Backdraft damper on the hood duct prevents air re-entering when the hood is off
- Best practice for Passive House and airtight new builds
Option 2 — Recirculating range hood
A recirculating range hood does not exhaust air outside — it draws air through a grease filter and a charcoal (activated carbon) filter, then returns it to the kitchen. Because no air is extracted from the building, there is no negative pressure issue and no duct penetration through the building envelope.
This is an appealing option in highly airtight homes — especially retrofits where cutting a new exhaust duct through the envelope would be difficult. The charcoal filter removes most cooking odours. However, there are genuine limitations:
Moisture is not removed
Recirculating hoods filter odours and grease but return all moisture to the kitchen air. In an airtight home where MVHR is managing humidity levels, high-moisture cooking — boiling, steaming — still needs to be managed by the MVHR extract in the kitchen zone.
Particulate removal is less effective
Charcoal filters do not capture ultrafine particulates (PM2.5) from high-temperature cooking as effectively as extraction to outside. Recent research indicates recirculating hoods leave more particulates in the indoor air than ducted extraction.
Filter maintenance is critical
Charcoal filters require replacement every 3–6 months. A saturated filter provides very little odour removal. This is often overlooked in practice.
Recirculating hoods are suitable when cooking is light and infrequent, strong-smelling or high-grease cooking is uncommon, and the MVHR system provides effective extraction in the kitchen zone. For most family homes with regular cooking, ducted extraction with make-up air is the better long-term solution.
Coordinating with your MVHR system
An MVHR system includes a kitchen extract terminal — but this is designed for background ventilation (continuous low-volume extraction), not for the peak load of active cooking. Do not assume the MVHR extract replaces a range hood; it does not.
If your home has a ducted range hood, it operates as a completely separate system from the MVHR. The two systems coexist: the MVHR provides continuous background ventilation, and the range hood handles cooking extraction on demand. The key coordination requirements are:
Backdraft dampers on the hood duct
Prevents outside air from entering the home through the extraction duct when the hood is not running.
Make-up air when extracting at high volume
A dedicated replacement air path prevents the range hood from depressurising the building.
Separate duct penetrations
Range hood and MVHR ducts should each have their own dedicated, sealed penetrations through the airtightness layer.
Early design coordination
Kitchen layout, cooktop position, duct routing and penetration locations need to be resolved at design stage — not during fitout.
Best practice summary
- 1.Use a ducted range hood vented outside — not recirculating — as the preferred solution
- 2.Design a make-up air path to balance extraction and maintain neutral building pressure
- 3.Specify a sealed backdraft damper on the extraction duct
- 4.Keep the range hood duct and MVHR ductwork entirely separate — they serve different functions
- 5.Coordinate kitchen ventilation requirements at design stage, before structure begins