Airtight but Healthy: Ventilation Strategy for Deep Renovation
Better airtightness reduces uncontrolled leakage, so ventilation design and commissioning must be planned as part of a deep renovation. The goal is not to prescribe one universal system, carbon-dioxide threshold or air-change rate. The right solution depends on the dwelling, the altered construction, the rooms and the occupants.
What changes when a home becomes airtight
Sealing gaps in the envelope can reduce unintended air movement through walls, roofs, floors and junctions. That makes the ventilation strategy more important: moisture, odours and pollutants still need a controlled route out, while fresh air must reach occupied rooms. Plan the ventilation design early, alongside insulation, windows and airtightness details.
Under the Dutch Bbl, a new dwelling’s living-area supply is generally at least 0.9 dm³/s per m², with a minimum of 7 dm³/s. For an existing dwelling, the general level is 0.7 dm³/s per m², also with a minimum of 7 dm³/s. Kitchens, bathrooms and toilets have separate extraction requirements. The applicable level depends on the work and the legally acquired level, so verify the requirement for the specific project.
Design the system for the actual home
Choose supply and extraction locations, duct routes, transfer paths and controls together. Living rooms and bedrooms generally need a route for supply air, while kitchens, bathrooms and toilets need extraction. Doors, grilles and internal gaps must allow air to move between these zones without creating avoidable noise or draughts.
System sizing should reflect the floor plan, occupancy and intended use. Consider acoustic performance, filters, maintenance access and the position of the equipment. Better airtightness can make a system easier to balance, but it does not make commissioning optional. Measure the airflow at the valves, record the settings and give the homeowner clear operating and maintenance instructions.
How to use CO2 and windows sensibly
RIVM describes carbon dioxide as a rough indicator of air exchange in occupied rooms, not as a guarantee of healthy indoor air. A sensor can help reveal patterns in a bedroom or living room, but it does not replace a complete assessment of moisture, particles, chemical pollutants, temperature and the operation of the ventilation system.
Continuous ventilation is important. RIVM advises keeping ventilation running; opening windows briefly can help after temporary pollution, but it does not replace ongoing ventilation. Avoid blocking supply or extraction valves and maintain filters and fans according to the system instructions. If moisture or odours persist, investigate the cause rather than relying on a single sensor value.
Plan and verify the work
- Assess the existing construction, ventilation routes, moisture risks and legally applicable Bbl level.
- Coordinate airtightness details, supply and extraction points, transfer paths, sound control and service access in the design.
- Select equipment and filters for the actual dwelling and occupancy, using manufacturer data and project calculations.
- Commission the installed system, measure airflows and document settings, controls and maintenance.
- Explain daily operation, filter replacement and the difference between continuous ventilation and brief purge ventilation.
A healthy result after renovation
A successful airtight renovation combines controlled air exchange with a well-detailed envelope. The design must balance energy use, moisture safety, acoustic comfort and practical maintenance. The system should be reviewed after occupancy if rooms, use or airtightness change. A project-specific design and proper commissioning are more reliable than a product list or one universal indoor-air target.
Official sources and next checks
Rules and product information can change. Before ordering or applying, check the sources that apply to the address and proposed work.
