Heat recovery ventilation systems provide fresh air to a home without compromising the overall energy efficiency of the dwelling.

Example of a whole house heat recovery ventilation system installed by GriffithsThe ventilation system provides constact fresh air to a property, which is boosted when wet rooms are usedGriffiths preferred ventilation system is the Polypipe HRX unit with a radial duct systemExample of radial duct system installed by Griffiths

Modern houses have become increasingly 'air tight', requiring some form of ventilation to prevent the build-up of volatile organic compounds (VOC's) i.e.. odours, humidity or chemical fumes.

Traditional forms of ventilation in houses (i.e.. opening windows) result in unfiltered air being introduced into the home. Which in winter means valuable heat energy escaping the property, conversely in the summer additional unrequired heat shall be gained.


Heat Recovery Ventilation Systems (M.V.H.R) comprise of a heat exchanger appliance and a central duct system supplying/extracting air throughout the home (Usually concealed within ceilings and voids).

Air is extracted from 'Wet' rooms (i.e. bathrooms, WC's and Kitchens), with fresh air supplied to 'habitable rooms' (I.e. living, dining, studies and bedrooms). 

The extracted air passes through a heat exchanger, pre-heating the fresh air entering the property (Please note that the extracted and fresh air are not mixed).

95% of the heat energy contained within the extracted air can be recovered to pre-heat the fresh air.

The systems have the option of a 'summer bypass' which fresh air bypasses the heat exchanger, bringing cooler air into the property.

The systems are setup to continuously extract/supply air to a property. However whenever a 'Wet room' is occupied, the system boosts the fan speed to provide additional air extraction.

Key Ventilation Terms Explained

'M.V.H.R' - Acronym meaning Mechanical Ventilation with Heat Recovery.

'Radial duct system' - Air is extracted/distributed throughout a property via 75mmØ ducts. These supply/extract specific amounts of air from individual rooms from a central 'plenum' box. Radial duct systems reduce the amount of noise transfer between rooms.

'Summer bypass' - The summer bypass is a specific diverting duct, installed on the heat recovery appliance, which diverts incoming fresh air around the heat exchanger. During summer months, when the external air temperature is higher than inside a house, the bypass is activated to prevent the system heating the incoming warm air.

During summer evenings (when the air temperature decreases)  the systems provide an element of 'Free Cooling' to a property.


  • Limitation of heat energy being lost through opening windows (In turn lowering heating bills).
  • Clean filtered air throughout a property reducing the buildup of V.O.C.'s and hayfever symptoms.
  • Can help to prevent 'sick building syndrome'.