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Semi-centralised supply and extract air system

with heat recovery via heat exchangers, constant air flow

If the layout of the building limits your options for a centrally sited air handling unit, e.g. in terraced housing, then you may need multiple medium-sized units so that each unit ventilates two or more housing units.

No extensive ductwork

A semi-centralised solution eliminates the need for extensive ducting, the advantage of which is relatively low system pressure falls, which in turn results in an energy-efficient and quiet system. Semi-centralised units can be served by a counterflow heat exchanger or a rotary heat exchanger.

The disadvantage, compared with a centralised system is that the number of service points increases, which then increases the servicing and maintenance costs.


  • Balanced ventilation
  • Reduced risk of draughts and noise
  • Several heat exchange options
  • Guaranteed indoor climate
  • Efficient heat recovery


  • Slightly more service points than in a centralised system
  • Slightly higher maintenance costs