Mechanical Ventilation with Heat Recovery (MVHR)
Breathe Better, Live Smarter Whole-Home Comfort through Mechanical Ventilation with Heat Recovery (MVHR)
Mechanical Ventilation with Heat Recovery (MVHR) is a type of ventilation system that mechanically extracts and supplies air, recovering heat from outgoing stale air and using it to warm up incoming air ensuring a continuous supply of fresh air. An MVHR system is a whole house ventilation system with heat recovery and supplies fresh air to all habitable rooms in a building (e.g. living rooms, dining rooms, bedrooms, studies, etc). It also removes moist stale air from bathrooms, kitchens, toilets and utility rooms, bringing fresh, filtered air into the house (which helps with indoor air quality, unlike other ventilation systems). As opposed to traditional ventilation systems, which ‘dispose of’ heat from the building via vents, an MVHR system can recover up to 96% of the heat from the air in the building and redistributes it to the habitable spaces. This makes it hugely beneficial in terms of reducing energy consumption, heating bills and your carbon footprint.
A well-designed MVHR system can significantly improve indoor air quality and energy efficiency in any property size, from small urban apartments to large luxury dwellings. MVHR systems maintain a comfortable, healthy indoor climate all year round. They are particularly beneficial in tightly sealed properties where traditional ventilation options are limited.
MVHR systems are not a replacement for air conditioning as they are not for cooling. We recommend cooling to come from dedicated air conditioning unit(s). The ComfoPost helps to reduce the supply air temperature of the MVHR unit in the summer months and if required increase it in the winter months. Chilled water is fed into the ComfoPost during the summer months typically by a chiller or reversible heat pump to help reduce the supply air to all habitable rooms in the property resulting in comfortable supply air during warmer periods. Please note that this is air tempering only and is designed to help take the peaks off the internal heat spikes. It is not air conditioning and this is an important distinction. We believe that with ComfoPost the temperature drop will be only a few degrees, provided the correct cooling load calculations have been done, and may not be adequate during hot weather that we are increasingly experiencing.
Enhance indoor air quality and energy efficiency through Mechanical Ventilation with Heat Recovery (MVHR)
Frequently asked questions (FAQs)
MVHR is essential in a Passive House. It also works well in near-Passive Houses and other modern houses with a good level of airtightness. MVHR can also be retrofitted into older houses. Since the system needs to accommodate ductwork throughout, this requires proper planning and is usually done as part of a wider renovation.
A unit is roughly the size of a washing machine. Generally, it is best to install it in a utility room or plant room, as you need to be able to get to it easily to change filters and carry out maintenance. We would not recommend MVHR units to be installed in loft spaces unless all other options have been exhausted. We would need to ensure the loft is properly insulated and accessible before considering this option as this may not be the best location for optimal performance. The loft can experience extreme temperature fluctuations, which can negatively impact the performance and efficiency of an MVHR unit. Furthermore, long intake ducts, which are likely when the unit is installed in the loft, can lead to more thermal loss and thus reduced heat recovery efficiency.
The earlier the better. When you have got planning permission you need to start planning your MVHR system and getting MVHR designs drawn. It’s possible to do it at a later stage but it is a lot more difficult and much better to factor in the MVHR before the build starts.
We will need to install ductwork before any 1st fix plumbing and electrics takes place. We will then return to install your MVHR unit(s) after your plastering has taken place, and at the same time that 2nd fix electrics and 2nd fix plumbing take place. We will then also complete any outstanding works to do with the installation.
In summer time there is no heat loss to consider and the system will operate in the background extracting moisture, so there is less of a concern about energy efficiency at this time of the year. However, if in the summer the house is colder inside than outside, keeping the windows closed will help keep the cool air inside and the MVHR system can recover the cool air via the heat exchanger as it does with the warm air in winter. In winter time, the bigger concern will be the loss of heat, so while you can certainly open the windows if you wish, you just need to be aware that it will reduce the efficiency of the system.
MVHR and Air Conditioning do not share ducting. The air sources for each are not shared, and should not use the same ducting. We have seen some designs where they share plenums, but this causes problems when it comes to commissioning air flows for the MVHR system. To commission the valves for an MVHR system, the valve must be isolated to record only air flows coming out of the specific valve. If there is a shared plenum, it can be time consuming and difficult to isolate just the MVHR supply air and can lead to incorrect or incomplete commissioning. Incorrect commissioning means the system may not operate to spec, and may be inefficient and costly to run.
Yes, you need a kitchen extractor but not one that goes to the outside. We would recommend you install a recirculating cooker hood. This type of cooker hood will filter any fat in the air. We would then specify an extraction vent in the MVHR system which will have its own filter. This provides a secondary line of defence in case there is any other fat in the air, while still removing any moisture and smells.
Yes, an MVHR system runs 24/7. The running costs per year are very low and the MVHR system only works effectively if it is switched on at all times – this is because it runs in ‘passive’ mode, and switches to ‘active’ mode only when it needs to remove damp air.
If designed and installed correctly, you should not notice any noise from your MVHR system unless it is a cheaper MVHR unit with noisy fan motors and the casing not well built and/or insulated.
Trickle Vents & Building Regulations Part F. No trickle vents should be installed if you have or are installing an MVHR system to avoid unintended air pathways. If you are using MVHR, each habitable room should have mechanical supply ventilation, with the air supply proportional to the size of the room.
It is very important to insulate the ducting that goes from the outside into the MVHR unit. This is because it stops condensation building up on the outside of the pipe when cold air comes into a warm house during the winter. Condensation build up can cause drips through the ceiling, and no one wants that!
We recommend either: (1) Rigid metal branch ducting with smooth ends for better airflow, double sealed for airtightness, anti-bacterial surface Or (2) Semi rigid radial ducting which bends easily without snapping. There is a big difference in the quality of ducting – e.g. pvc ducting has very sharp ends which creates huge resistance for the airflow which makes it more energy hungry and noisy. It also has questionable hygienic properties after long term use as you can get mould and fungus in the ductwork.
Completed Projects
Let’s connect today
Have a query or need expert guidance on renewable energy solutions? Our friendly team is here to help so contact us and let’s build a greener future together.
SEND US A MESSAGE
CONTACT INFORMATION
GREEN HOME ENERGY
402, Uxbridge Road, Hatch End, Middlesex HA5 4HP, United Kingdom.
Do you have questions about our services & solutions? Send us an email and we’ll get in touch shortly.
Follow Us
Connect with us to discover the latest in green energy, expert tips and exclusive offers. It only takes a second to stay informed and power your home sustainably!
