Mechanical Ventilation with Heat Recovery (MVHR) can keep your home fresh, dry and energy efficient, especially in new builds and airtight renovations around Greater Manchester. To get the best from it, you need a simple, regular maintenance routine that any homeowner can follow.
MVHR basics you can safely check yourself
Your MVHR unit runs quietly in the background, constantly swapping stale air for fresh air while recovering heat. Most day-to-day checks can be done without tools and without opening the main unit.
Think of it like a boiler and radiators: the unit is the boiler, while valves and grilles are the radiators. You can safely clean and visually inspect the parts you can see, but internal adjustments are best left to a qualified engineer.
Printable MVHR maintenance checklist
Use this quick checklist as a guide. Keep it somewhere handy and tick items off every few months.
Every month: Walk round the house and feel air from vents; listen for new noises; check for condensation on windows.
Every 3 months: Lightly clean supply and extract valves and grilles; inspect visible duct grilles outside for debris.
Every 6–12 months: Check and replace filters as needed (more often with pets, nearby roads or building dust).
Annually: Book a professional MVHR service for airflow checks, full clean and safety inspection.
Looking after MVHR filters
MVHR systems usually have two main filters: a supply filter that cleans incoming fresh air and an extract filter that protects the unit from dust drawn out of your rooms. Both need regular attention.
Most manufacturers suggest filter replacement every 6–12 months. If you have pets, live near busy roads, or have ongoing building or DIY dust, aim closer to every 6 months. Always follow the instructions for your specific unit.
Tell-tale signs your filters are blocked
You do not need to open anything to notice symptoms of clogged filters. Your home will often tell you something is wrong before the unit does.
Common signs include:
Rooms feeling stuffy or “heavy” even with the system running
More condensation on windows, especially in bedrooms and bathrooms
Stronger cooking smells that linger for longer than usual
Fans sounding louder or working at a higher speed than before
If you notice these, it is a strong hint that your filters are due a change and the system may also benefit from a professional service.
Understanding reduced airflow and draughts
Healthy MVHR airflow should feel gentle, not like a fan blasting air at you. At supply vents, you might just feel a light movement when you hold the back of your hand close to the grille.
Reduced airflow can feel like almost nothing coming from supply vents, or extraction in bathrooms that no longer clears steam as quickly. Mirrors fog up for longer and rooms take more time to feel fresh after showers or cooking.
On the other hand, if air from a vent feels very strong or “draughty”, or one room feels much colder, it can indicate the system is not balanced correctly. This usually points to a commissioning issue rather than a simple cleaning job.
Basic hygiene: cleaning valves, grilles and drains
You can safely clean the parts of the MVHR system you can reach without removing covers from the main unit. Regular surface cleaning helps air move freely and keeps dust levels lower.
Gently wipe supply and extract valves and grilles with a slightly damp cloth, avoiding harsh chemicals. Do not twist or unscrew the discs or cones on the valves, as this can disturb the carefully balanced airflow between rooms.
If your system has a visible condensate drain near the unit, visually check that it is not kinked, blocked or dripping. Clear any obvious debris from the trap outlet, but avoid taking it apart unless you know what you are doing.
Troubleshooting common MVHR complaints
Small changes in sound or comfort are often your first warning that the system needs attention. Here are some frequent issues and what they usually mean.
Whistling vents
Whistling or “singing” vents are usually caused by air moving too fast through a valve or grille. This can happen if the system was never properly balanced, or if someone has altered valve positions while decorating or cleaning.
Do not keep turning valves in the hope of fixing the noise, as this can upset the balance further. Make a note of which rooms are affected and ask a professional to re-balance the system.
Noisy unit
If the main MVHR unit seems louder than usual, the fans may be working harder because of clogged filters or restricted ductwork. Sometimes the system has automatically increased speed to compensate for blockages.
Start by checking whether your control panel shows any filter or fault warnings. If the noise continues after filters are changed, it is time for a service to check fans, internal cleanliness and airflow settings.
Draughts and cold spots
MVHR is designed to supply low-level air, not strong draughts. If one room has noticeably cold air blowing in, it may have been set too high at commissioning or altered later by accident.
Covering vents with furniture or curtains can force more air through fewer grilles, creating noticeable streams of air. Keep vents clear and ask an engineer to measure and balance airflow if discomfort continues.
Lingering odours
Persistent cooking smells, bathroom odours or general mustiness usually suggest reduced extraction rather than a problem with the fresh air supply. Blocked extract filters or dirty bathroom/kitchen valves are common culprits.
If cleaning the visible grilles and replacing filters does not help, the system may not have been correctly commissioned, or ductwork could be partially blocked. Professional airflow testing will identify where the problem lies.
What a professional MVHR service includes
While regular light cleaning is a good DIY task, a full MVHR service needs specialist tools and knowledge. It goes far beyond a quick filter change.
A typical professional service will include:
Accurate airflow measurement in key rooms to check the system is delivering the design rates and to correct any imbalances that cause noise or draughts.
Heat exchanger inspection and cleaning to remove dust, debris or microbial growth, helping maintain efficiency and indoor air quality.
Condensate and controls checks to ensure drains are clear, sensors are working correctly and fan speeds respond as they should to humidity or boost switches.
Safety notes: when not to DIY
It is important not to open the main MVHR unit casing or interfere with electrical connections unless you are qualified. Internal components can be delicate, and incorrect refitting can lead to leaks or faults.
If in doubt, keep your own work to visual checks, gentle surface cleaning and following manufacturer guidance on filters. Anything involving wiring, internal parts, or air balancing should be passed to a professional.
Need help with MVHR maintenance or noise?
Regular, simple checks will keep your MVHR system running quietly and efficiently, but if you are dealing with ongoing noise, draughts or stale air, it is time for a proper inspection. A well-maintained system will protect your home from condensation and help keep energy bills under control.
For friendly, expert MVHR servicing and maintenance in your home, contact Ab plumbing and maintenance on 01204888255 to book an inspection or annual service.
