Energy

Designing homes to conserve energy and use it efficiently, from sources that cause least environmental harm.

Air supply ventilation systems

Mechanical ventilation systems may be specified to ensure sufficient air flow in an airtight building or in specific rooms. Only a small amount of energy is required for air movement, but this will increase if incoming air must also be heated.

A range of mechanical ventilation systems are available including heat and energy recovery ventilation, positive pressure/forced air, solar energy heating/ventilation and ducted warm air transfer.

Find out about:

  • components of an air supply ventilation system
  • fresh air quality
  • flow rates
  • energy use
  • fresh air heating.

Components of an air supply ventilation system

Mechanical air supply ventilation is generally by fan, which may be stand-alone or part of an air conditioning or heat recovery system. To move fresh air from outside to indoors also requires an air intake, air filter, ductwork and room diffusers.

Fresh air quality

In order for the fresh air being introduced to be better quality than the air it is replacing, the system requires:

  • an air filter to remove particulates
  • locating an air intake where it will not draw in polluted air.

Flow rates

Most fresh air ventilation supply systems are designed to run continuously, with fresh air flow rates at around 3–20 litres per second.

Energy use

In general, as more air is moved by the fan, more energy is consumed. To minimise energy use, fans should be sized and controlled to move only the amount of ventilation air required for the time required.

Fresh air heating

Many fresh air supply ventilation systems provide some heat to the supply air flow before it is drawn indoors. Heating air brought from outside can consume substantial amounts of energy, particularly in winter when the outdoor air temperature is low. This can be reduced by installing a heat recovery ventilation system or by designing the system so that the fresh air:

  • volume flow rate is kept to appropriate levels
  • intake is located to capture warmer outside air, e.g. on the sunny side of the building, near warm surfaces or from spaces with solar gain storage
  • is only heated when the outside air temperature is cold (below about 13ºC) or is 6ºC below the required room temperature – this depends on the heating system and level of heat gains from other sources in the room
  • is not heated more than to make the occupants comfortable.