MVHR - Frequently Asked Questions


How do MVHR systems work?

Fresh air is continuously drawn into the home via low energy ventilation unit, located in the roof space/utility area of your home. The ventilation unit filters the incoming air to remove pollutants and insects. Once passed through the heat exchanger within the power unit, the warm, fresh filtered air is distributed around the home through a series of ducts which are run to each habitable room i.e. living room, bedroom etc. The air from wet rooms i.e. bathrooms, kitchens, WC’s, utility areas etc. is continuously extracted and filtered back through ventilation unit. The heat from the extracted air is transferred to the fresh incoming air.


How much heat is recovered?

An MVHR system is designed to recover up to 95% of the heat normally lost in the property is through open windows, trickle vents and other break-out points i.e. extractor fans in a building structure. The air being extracted transfers its latent heat via a heat exchanger to the fresh air coming in. The heat recovered can off-set the heating costs and will reduce energy bills.


Will the indoor air quality in my home be improved?

Studies show there is a direct connection between the quality of air (caused by poor ventilation) and our ability to concentrate and perform productively, as well as the effect poor indoor air quality has on asthma or allergy sufferers. The ventilation unit filters the incoming air to remove pollutants and insects and the constant supply of clean, fresh, warm filtered air reduces symptoms for asthma and allergy sufferers.


Can a heat recovery ventilation system be installed in my existing home?

Yes it can be, (subject to a survey of your property- ask us for more details)


Is it noisy?

MVHR systems are designed to have minimal noise impacts and they should run almost silently. It is important to not block any of the air vents as this will put the whole system out of balance. To ensure the machine works at its quietest, have an approved installer to check the machine is balanced correctly.


Will it heat my house?

No, MVHR will re-use the heat which already exists in your home produced by occupants and electrical equipment. Some systems can be designed to have an additional in line heater, to heat supply air, but this can only provide a small amount of heating.


What maintenance do I need to do?

Apart from keeping all the air vents clear and clean, the only maintenance is periodic filter changes. There are several filters which may need to be changed to keep the air flowing properly. How frequently, depends on where you live and how clean the air is. The filters keep your air clean, but are also required to keep the system working properly. Normally filters need to be changed every 12-18 months; however your system will alert you when this needs to be done. We also recommend a service is carried out the MVHR units every 12-18 months.


Can I open the windows?

MVHR supplies fresh air to all habitable rooms, it also removes moist stale air, reusing the heat to pre-heat the fresh air entering the building


Does the system run 24/7 for 365 days of the year?

It is set for automatic use all year round so you do not have to adjust any settings. However you may want to over-ride the automatic system on some occasions e.g. holiday mod & summer bypass


Is the system expensive to run?

With the newest generation EC low energy fans fitted, running costs are very low (approximately the equivalent of a light bulb to run)


What do I do when I go on holiday?

You can reduce the ventilation while you are away. Simply go to your control panel and reduce the fan speed to minimum. When you return home just return to the standard setting and your system will return to normal operation.
What should I do if there are more people in the house?

You can increase the ventilation through the boost mode. Simply go to your control panel and select the boost mode, which will increase the fan speed. When people have left, return to the normal ventilation setting, which will keep the air feeling fresh. Some machines have an automatic boost, when the humidity reaches certain levels.


What happens if the electricity supply is cut off?

You may start to feel that the air is becoming a little stale. In the unlikely event that it happens whilst you are asleep, then your bedroom might seem a bit stuffy in the morning.


Can I install the system myself?

Yes, certain systems are sold for DIY installation or a completely installed basis by one of our fully trained engineers. A detailed installation manual comes complete with every system. If the system is a supply only, once fully installed, the system will need to be commissioned by a fully qualified engineer to ensure the airflow rates are correct and the system is running efficiently (this is required by Building Control)


How can I ensure compliance with current Building Regulations?

All MVHR units that we supply/ install have been tested to ensure they comply with building regulations. The units are SAP Appendix Q listed, and they help improve SAP/ BER ratings.


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