Mechanical Ventilation with Heat Recovery systems, commonly known as MVHR, have become a central feature of modern energy-efficient homes. Designed to extract stale air from kitchens and bathrooms while supplying filtered fresh air to living spaces, these systems recover heat that would otherwise be lost. Brands such as Vent-Axia, Zehnder, and Nuaire have helped popularise MVHR technology across residential and light commercial buildings. However, like any mechanical system, MVHR units require maintenance and occasional repairs to maintain performance, efficiency, and indoor air quality.
MVHR repairs often begin with diagnosing reduced airflow. Homeowners may notice condensation forming on windows, lingering cooking smells, or rooms that feel stuffy despite the system running continuously. These signs can indicate blocked filters, obstructed ductwork, or failing fans. Filters are typically the first component to check, as they collect dust, pollen, and airborne particles. When neglected, clogged filters restrict airflow, forcing the system to work harder and increasing wear on internal components. Replacing filters at recommended intervals can prevent more complex and costly repairs later.
Another common issue involves the heat exchanger core. The heat exchanger is responsible for transferring warmth from outgoing stale air to incoming fresh air without mixing the two air streams. Over time, dust accumulation or moisture build-up can reduce its efficiency. In some cases, improper installation or poor sealing can cause cross-contamination between airflows, leading to unpleasant odours or reduced heat recovery performance. Repairing or replacing a heat exchanger requires technical expertise, as the unit must be carefully dismantled and reassembled to maintain airtightness.
Fan motor failure is another repair scenario frequently encountered. MVHR systems operate continuously at low speed, meaning the fans are under constant demand. Bearing wear, electrical faults, or control board issues can cause unusual noises, vibrations, or complete system shutdown. When this occurs, a qualified technician will test the motor, inspect wiring connections, and assess the control unit. In some cases, replacing the fan assembly is more MVHR repairs cost-effective than attempting individual component repairs, particularly in older systems.
Condensate drainage problems can also compromise MVHR performance. Because warm air cools as it passes through the heat exchanger, condensation naturally forms within the unit. This moisture must drain away properly through a dedicated condensate line. Blockages or poor installation angles can cause water to accumulate inside the unit, leading to leaks or internal damage. Repairing drainage issues may involve clearing blockages, adjusting pipe gradients, or installing insulation to prevent freezing in colder climates.
Control systems and sensors play a crucial role in modern MVHR units. Many systems include humidity sensors, boost controls, and programmable settings that optimise airflow based on occupancy. When sensors malfunction or controls fail, the system may not respond correctly to changes in indoor conditions. Repairs may require recalibration, software updates, or replacement of faulty circuit boards. Because these components are integral to energy efficiency, prompt attention ensures the system continues to operate as designed.
Ductwork integrity is another important aspect of MVHR repair. Flexible ducts can become crushed or disconnected, while rigid ducts may develop leaks at joints. Even small air leaks reduce system efficiency and disturb balanced airflow. Professional technicians use airflow measurement tools to rebalance the system after repairs, ensuring that supply and extract rates remain equal. Proper balancing is essential to prevent pressure imbalances that could draw in unfiltered air from outside or from wall cavities.
Preventative maintenance significantly reduces the need for major MVHR repairs. Regular servicing, including filter changes, internal cleaning, and airflow checks, keeps systems functioning efficiently for many years. While some minor maintenance tasks can be performed by homeowners, more technical repairs should always be handled by trained professionals familiar with manufacturer guidelines. With proper care and timely intervention, MVHR systems continue to provide fresh, filtered air and consistent energy savings, protecting both building fabric and occupant health.
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