MVHR (mechanical ventilation with heat recovery), MEV (mechanical extract ventilation) and Air Conditioning Options from Vent-Axia, Greenwood & Delonghi.
MVHR (mechanical ventilation with heat recovery) is a whole dwelling ventilation system that supplies and extracts air continuously at a low rate with the facility to be boosted as required meeting Building Regulations Part F System 4. The unit is normally installed in the loft space or cupboard and rigid ducting supplies fresh filtered air to the habitable rooms and extracts stale polluted air from the wet rooms. Supply and extract diffusers are fitted to the ceilings and are adjusted to balance the system.
Centralised mechanical extract ventilation (MEV) follows the same principle as MVHR except it does not include any heat recovery. A central unit is mounted in a loft or cupboard and ducted to extract polluted air from the wet rooms of the house. As there is no heat recovery, there is no requirement for any ducts to supply the replacement air. Instead, replacement air enters the home through window vents or airbricks. In many houses however, air naturally enters the building through gaps and cracks in the structure, providing adequate ventilation.