MVHR maintenance: the step that's too often overlooked

Why MVHR maintenance protects air quality and prevents breakdowns

Indoor air quality: what a fouled MVHR system can no longer do

A fouled MVHR system loses airflow. It no longer properly clears humidity, odours, and some everyday pollutants. The result is stagnant air, rising condensation, and mould finding the perfect breeding ground. Regular maintenance of vents, air inlets, and, on heat-recovery systems, filters, keeps ventilation genuinely effective.

Power draw and noise: the signs that should put you on alert

When ducts, vents, or filters build up with dust, the fan strains. You may see consumption rise and hear whistling, vibrations, or an unusual hum. These signals are often the start of a network imbalance or an overheating motor. Better to step in before the breakdown.

Unit lifespan: what you gain from regular maintenance

Cleaning, checking the fixings, inspecting the ducts, and dusting the unit limit mechanical and electrical wear. You avoid sudden shutdowns, emergency repairs, and parts replaced too soon. In short, you extend the unit's lifespan and secure stable day-to-day operation. To go further on losses and defects linked to the network, see also duct condition.

Points to check on an MVHR system: your field checklist

Extract vents and air inlets: cleaning without disturbing the settings

Cut the power. Unclip the grilles, then wash them in warm soapy water. On a humidity-controlled system, don't dismantle the sensitive part. Check that no paint or dust is blocking the passage. On the air inlet side, vacuum gently without wetting it, and check that the dampers open properly.

Ductwork: spotting crush points, leaks and condensation

Follow the ducts from the unit to the vents. Look for a crushed section, a disconnected fitting, or an air leak. Also watch for water marks. Condensation and mould often point to poorly insulated ducting or a slope that traps water. Refasten with clips and aluminium tape.

Motor, unit and connections: dusting, fixings, airtightness

Open the unit. Dust the fan wheel. On a heat-recovery system, clean or replace the filters. Check the fixings, the anti-vibration mounts, and that the clips are tight. Listen for abnormal noise. If you have a measuring instrument, check the airflow rates and note any discrepancies.

Maintenance method by MVHR type (single-flow, humidity-controlled, heat-recovery)

Single-flow MVHR: frequency and effective steps without unnecessary dismantling

Cut the power. Every 3 months, dust the vents and air inlets with a vacuum and a slightly damp cloth. The goal is simple: keep a good airflow without opening the unit if everything is working.

Humidity-controlled MVHR: precautions to avoid throwing off the sensors

On a humidity-controlled system, avoid getting water on the humidity-controlled vents. Dry cleaning, a soft brush and vacuuming, limits the risk of sticking or skewing the sensors. Don't block the slots, they drive the opening.

Heat-recovery MVHR: filters, exchanger and the risk of dropping efficiency

Change or clean the filters every 3 to 6 months depending on fouling. Once a year, check the exchanger, the condensate tray, and the airtightness. Clogged filters cause efficiency to drop and increase noise: to go further, see how a thermodynamic heat-recovery MVHR system combines ventilation and heating.

Maintenance frequency in 2026: what you can schedule for your clients

Recommended pace: monthly, half-yearly, yearly depending on use and environment

For an MVHR system that stands the test of time, offer a simple schedule to follow. In an occupied dwelling, the use of wet rooms and dust quickly cause airflow rates to drift.

• Monthly. Visual check, noise, vibrations, grilles not obstructed.
• Half-yearly. Cleaning of vents and air inlets. Check on condensate and fixings.
• Yearly. Airflow measurement, unit check, electrical tightening. On heat-recovery systems, filter replacement depending on fouling.

Maintenance log: tracking your interventions and securing follow-up

In 2026, a clear log, paper or digital, saves time. Note dates, actions, part references, measured airflow rates, before/after photos, and anomalies. It's your proof of follow-up, useful for warranty claims and when an occupant changes.

When to propose an upgrade: replacing vents, ducts, unit

Propose an upgrade if the vents are broken or fouled despite cleaning, if the ducts are crushed, punctured, or show signs of moisture, or if the unit becomes noisy and can no longer hold its airflow. After 10 to 15 years, a replacement can reduce breakdowns and improve air quality, especially in a dusty environment. To go further on sizing the terminals, see vents and air inlets.

Common mistakes and best practices for a lasting MVHR system

Aggressive cleaning: products, water, blowing... what to avoid

On an MVHR system, the "big clean" reflex can do more harm than good. Avoid bleach, solvents, and strong degreasers. Don't drench the vents or spray water into the unit. Also skip compressed-air blowing, which can push dust into the motor and wear out the bearings. Favour gentle dusting, a slightly damp cloth and, where fitted, regular filter replacement.

Settings and airflow: how to check without unbalancing the installation

Adjusting settings "by ear" often ends in under-ventilation. Check the regulatory ventilation airflow rates with a measuring instrument and keep the original positions. Never block the air inlets. A simple mapping of the vents, followed by a room-by-room check, limits mistakes and keeps the network balanced.

Job-site safety: power cut-off, loft access and dust

Before any work, switch off at the breaker and check for the absence of voltage. In lofts, secure access and the walkway. Insulation dust irritates quickly. Wear a mask, goggles, and gloves. In older renovations, stay alert for hazardous materials before drilling.