Mechanical ventilation: the cheapest maintenance nobody thinks about

A stopped ventilation unit is neither seen nor heard, and costs the building thousands in damp repairs.

Mechanical ventilation is one of those systems nobody discusses while it works. It does not fail loudly: it clogs, loses airflow, then stops. Meanwhile damp settles into flats, and the building ends up treating mould whose cause it does not understand.

Yet it is one of the cheapest maintenance items relative to what it prevents. A board that puts this back on the agenda does occupants a very concrete service.

What ventilation is actually for

A home continuously produces moisture: breathing, cooking, showers, drying laundry. Without air renewal that vapour condenses on cold surfaces and causes mould. Ventilation extracts air from wet rooms — kitchen, bathroom, WC — and replaces it with air entering through the window frames.

The system only works if both ends are clear. That is the least understood point: blocking a façade air inlet because an occupant feels cold stops air renewal in the whole flat.

What falls to the association

• The extraction unit, usually on the roof or in the loft, with its motor.
• The collective ducts running through the building.
• The control components and airflow verification.
• Periodic maintenance and replacing the motor at end of life.

Routine cleaning of the vents inside a flat, and keeping air inlets clear, generally fall to the occupant. The exact boundary is in the building rules, and the general principle in private works and common areas.

The maintenance contract: what to check

Many buildings pay for maintenance without ever reading the intervention reports. Yet those reveal the system’s real condition.

• Could the contractor access the unit at every visit?
• Were airflows measured, and are they compliant?
• Is cleaning the collective ducts included, or billed separately?
• Do the same reservations recur year after year without being cleared?
• Is the motor’s age known, and its replacement anticipated in the works plan?

This fits naturally into the recurring-contract review described in the cleaning contract specification.

The direct link with damp

When several flats report mould in corners, around windows or in bathrooms, ventilation is the first suspect — well before ingress. A ventilation fault shows three signs: it affects several flats, it worsens in winter, and it concentrates on cold surfaces.

Before voting waterproofing works, have the ventilation checked: see telling damp, condensation and ingress apart.

What the board can do this year

Three simple actions: ask for three years of maintenance reports, check during the annual walk-through that the unit runs and the grilles are clear, and remind occupants not to block air inlets.

That reminder, sent once a year before winter, costs ten minutes: see how to structure such a message and the annual walk-through checklist.

Before hunting for a leak, check the ventilation: it is free, and it is the cause in most mould cases.

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