Ventilation
Building work and ventilation: protect it during the job, clean it after
During building work the ventilation keeps extracting. Plaster, concrete and wood dust ends up in the ducts, filters and unit, often within days.
Published on · 6 min read
Mechanical ventilation is designed to extract air from wet rooms continuously. During building work it also extracts everything floating in that air: sanding dust, plaster, concrete, sawdust. What a building site produces in a week, an ordinary home takes years to accumulate.
The good news is that most of the damage can be avoided with a few simple precautions. And if the harm is done, it can be put right, provided you work in the right order.
Why building work clogs ventilation so fast
Building dust is very fine and very plentiful. It passes through the valves, clogs filters within days and settles on duct walls. Mixed with bathroom moisture or kitchen grease, it forms a crust that a vacuum cleaner will not shift.
The unit suffers too. Dirty fans become unbalanced and noisy, the motor strains, and on a heat-recovery system the exchanger loses part of its efficiency.
During the work: the right habits
- 1In rooms where sanding, demolition or cutting takes place, cover the valves with plastic film and masking tape for the dusty phases.
- 2If your system allows it, run it on its lowest setting during those phases, without switching it off for days if the home is occupied.
- 3On a heat-recovery system, check the filters halfway through: a clogged supply filter lets through what it should stop.
- 4Remove every cover as soon as the dusty work is over. A valve forgotten under its film is a room that is no longer ventilated.
Do not switch the ventilation off during plastering
After the work: the order to put things right
- 1Wait until the dusty phases and the final site clean are over. Cleaning earlier means paying twice.
- 2Replace the filters, even if they are less than a year old: they have seen in weeks what they normally see in years.
- 3Remove a valve and look into the duct. If a deposit is visible to the naked eye, the network needs cleaning; if in doubt, a camera inspection settles it.
- 4Have the unit cleaned along with the ducts: clean ducts behind dirty fans solve nothing.
We charge a fixed price per system for duct cleaning, from €199 excl. VAT for an extract-only system, on quotation. When the unit also needs attention, the service + cleaning pack covers everything in one visit.
Major renovation: ventilation matters more, not less
New windows or an insulated roof or walls make a home far more airtight. Air no longer changes through leaks, and mechanical ventilation becomes the only way in and out. A dirty or badly balanced system, tolerable in a draughty house, then becomes a damp problem.
After such a renovation, a full service, and an airflow check at the valves if needed, confirms that the ventilation matches the new level of airtightness.
Frequently asked questions
Should my contractor pay for cleaning the ventilation?
It depends on what the contract said, particularly about protecting existing equipment. If the work clogged a system that was left unprotected, settle it with the contractor, with photos as evidence. Inspection photos taken before and after cleaning exist precisely to document the network's condition.
How long after the work should I have it cleaned?
Once the last dusty phase is over and the home has been cleaned, not before. In the meantime, replacing the filters is enough to protect the unit.
Can work in another room clog the whole ventilation?
Yes. Dust spreads through the whole home and is drawn in by the wet-room valves, even far from the work. On a heat-recovery system, clogged filters can also let it be blown back around.