MVHR (or Mechanical Ventilation with Heat Recovery) is the process of delivering fresh filtered air into your building without creating uncomfortable drafts, and without creating excessive demand on your heating and cooling systems.

It works by recovering the thermal energy from the air within the building and using this to precondition the outside fresh air as it is drawn into the building.

It works equally well in both summer and winter. Smart controls on modern units control a bypass flap that allows the unit to bring in fresh air directly without passing it through the heat exchanger.

This allows better thermal and humidity control, and delivers even more comfortable and healthy indoor air quality.

Careful design ensures that MVHR power consumption and noise levels are kept low.

It's important to remember that MVHR is for indoor air quality control and not for heating or cooling buildings (the heating and cooling loads are predominantly determined by the design, and the performance of your building fabric components such as windows and insulation levels).

It's also important to consider building air tightness when planning the use of high quality MVHR, as the uncontrolled infiltration of air into the building that occurs in leaky buildings, will significantly effect the overall air quality when more efficient to do so.