Mechanical ventilation with heat recovery (MVHR)

Central mechanical ventilation units extract stale, moist air from wet rooms and some also supply fresh, clean air to habitable rooms. To do this they need a ductwork system with the following components:

Roof and/or wall terminals, which penetrate the building fabric
Air-tight seals for the terminals in warm loft spaces to keep the building fabric air-tight
Often insulated mass flow ductwork between the terminals and the ventilation unit to minimise the risk of condensation
Sound attenuators downstream of the ventilation unit to minimise noise hindrance
Ductwork systems between the ventilation unit and rooms to distribute air to and from them
Supply and/or extract valves in the rooms

More information

Detailed information

The installed performance of a ventilation unit depends upon the quality of the ductwork system. Ductwork systems are perfectly airtight on the screen or paper, but not installed. If a ductwork system leaks, then the fans have to work harder to overcome the leakage and ventilate the rooms at the design/hygienic flow rate. The higher the flow rate, the higher the pressure loss = more fan energy use and sound production.

Characteristics of high performance ductwork systems:

Low air velocity to minimise sound production
Low system pressure loss to minimise fan energy use and sound production
Air-tight to minimise fan energy use and sound production
Insulated to minimise the risk of condensation
Minimal transfer of sound/noise between rooms
Easy, quick, safe and clean installation
Commissioned correctly
Healthy and safe
Easy to clean

Regulations

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