Heat Recovery Ventilation (MVHR)

MVHR is an abbreviation for Mechanical Ventilation with Heat Recovery.  It works on the same principal as Mechanical Extract Ventilation (MEV) but includes a heat exchanger that uses the warmth of the air being extracted from the house to heat the air that is being drawn in to replace it.

A heat recovery ventilation system works by extracting moist and stale air from wet rooms in your home, it recovers the usually lost heat from the extracted air. It also supplies clean, filtered fresh air that is heated from the recovered warmth of the extracted heat.

Heat recovery ventilation, also known as mechanical ventilation heat recovery, is an energy recovery ventilation system which works between two sources at different temperatures. Heat recovery is a method which is increasingly used to reduce the heating and cooling demands of buildings.

A Mechanical Heat Recovery Ventilation (MVHR) is a system that works to extract excess moisture in the air yet also recovers the heat, meaning that it provides your home with ventilated air but doesn't take out any necessary warmth.

A MVHR unit can make your home more energy efficient when installed correctly, extracting moisture caused by condensation which can be especially prevalent in wet rooms like bathrooms and kitchens. All of our MVHR products are manufactured here in the UK and offer a wide range of innovative benefits in addition to exceptional performance and low maintenance.

It can be difficult to know which is the best heat recovery ventilation system for your property which is why we offer a free home survey, to assess your ventilation needs and advise on the best option.

MVHR or Mechanical Ventilation with Heat Recovery, recovers heat at ceiling level from the wet rooms (bathroom, en suite, kitchen, utility room) and stores it in a high-efficiency heat exchange cell. It then re-distributes this filtered and tempered air into the habitable rooms; however, it should not be used as a source of heating the home.

MVHR solutions work in conjunction with your existing heating system – they capture the warmth from radiators and heaters and use this, rather than being a heat source themselves.

MVHR recovers heat at ceiling level from wet rooms, stores this heat and re-distributes to habitable rooms such as living rooms and bedrooms.

When this recovered heat is not needed i.e., during the summer, the supply air will be diverted around the heat cell.

MVHR offers a completely balanced system, providing both extract ventilation and a supply of fresh heated air. It extracts moisture laden air from wet rooms/kitchens and supplies fresh, filtered heated air, to habitable rooms such as bedrooms and living rooms. MEV is also a whole house ventilation system but provides just extract ventilation from wet rooms and kitchens.

Both MEV and MVHR systems are most suitable for new properties rather than retrofit, but MVHR systems do require a more airtight property where virtually all of the air flow can pass through the heat exchanger, if they are to perform efficiently.

With inner cities obviously having higher pollution levels, MVHR systems are seen as more suitable because of the filter element, but in apartment blocks it’s often the case that only the first four floors are fitted with MVHR and the remaining with MEV as polluted air is heavier and therefore stays closer to the ground.

While MVHR (and MEV) systems both work on the principle of creating negative air pressure in a building by actively pushing air outdoors to be passively replaced by the fresh exterior air, Positive Input Ventilation (PIV) systems work by actively drawing in cool fresh air from outside and allowing the moist stale air in your home to escape naturally.

MVHR systems include a heat exchanger to minimise heat loss and are highly efficient.

Put simply, a heat exchanger is a device which transfers heat from one medium to another.

Heat is transferred by conduction through the exchanger materials which separate the mediums being used. A shell and tube heat exchanger passes fluids through and over tubes, whereas an air-cooled heat exchanger passes cool air through a core of fins to cool a liquid.

MVHR Systems provide controlled ventilation with slow but constant air movements. In contrast, natural ventilation (with intermittent fans) through background ventilators (trickle vents) is a form of uncontrolled ventilation, which fluctuates with wind speeds, temperatures, internal obstructions, such as the opening or closure of internal doors, trickle vents, blinds, and curtains. Therefore, it is recommended to install MVHR systems in more airtight energy efficient properties. For example properties with an air permeability less than (<) 5m³/(h.m²) @50Pa.

Besides the drive to make houses more efficient, there are other reasons, which lead towards the installation of MVHR systems:

Noise: if a property suffers from noise, e.g., traffic or airport, MVHR systems can provide a good solution for ventilation where there is an external noise concern.  Additionally, noise reduced glazing will help.

Air quality: if the air quality is problematic, e.g., for people suffering from hay fever, various kind of filtration in MVHR systems can deal with pollen, rural and industrial smells. Also, the position of the air intake can be carefully chosen in order to avoid the intake of polluted air from nearby roads.

High levels of humidity: Besides constant ventilation, MVHR systems will actively reduce internal humidity levels.