What other aspects of the ventilation system should be considered when designing a house?

There are many things to consider when designing a house to ensure the heat recovery system can be installed correctly and will perform as efficiently as possible.

  • Location of the MVHR unit.
    • The unit should be installed within the thermal envelope of the house to ensure maximum efficiency.
    • The MVHR unit itself should be installed centrally within the house as this assists in the correct distribution of air.
    • MVHR units should not be installed near bedrooms where possible. If installing in the attic or other space the unit a suitably insulated unit should be chosen.
    • Safe access to the unit should also be ensured to allow for regular maintenance of the system.
  • Access to atmosphere.
    • Every MVHR system must be ducted to atmosphere. One duct to carry the fresh air in to the house and another through which the stale air is exhausted. These ducts can be anywhere between 150mm and 250mm in diameter depending on the volume of air required. Cowls can be wall or roof mounted. Ventilation poles can also be installed where MVHR units are installed in basements. (link to ventilation poles here)
  • Condensate drain.
    • Most MVHR units, except for units that use rotary wheel units, need to have a condensate drain fitted. This should be plumbed into the waste water system within the house. It should not be piped directly to atmosphere such as a down pipe or gutter as it may freeze in cold conditions causing the water to overflow from the MVHR unit.
  • Prevailing winds.
    • It is important that the air intake and exhaust are as sheltered as possible.
  • Distance between supply and exhaust cowls.
    • A minimum of 1.2m is recommended between them. Consideration should also be given to the prevailing wind by keeping the exhaust cowl downwind where possible.
    • The supply cowl should be kept as far away from the chimney as possible, again, with consideration given to prevailing wind direction.

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