If you work in an air conditioned office, up to half the building's energy use will go on heating, ventilating and cooling the building. This can be a highly technical area, so use the pointers provided here as discussion topics with your consultant.


  • Older cooling systems may use chlorofluorocarbons (CFCs) that deplete the ozone layer and are active greenhouse gases. (Look for alternative cooling agents.)
  • Inefficient heating/cooling systems increase energy use.

Maximise natural ventilation

  • If possible, have windows that open so you can naturally ventilate the office. If this is not an option make sure the air quality is regularly assessed to avoid sick building syndrome. Avoid overheating in summer months - look for summer shading ideas (eg, trees, climbers or blinds).

Insulate your office

  • Ensure the building is properly insulated above 'building code' requirements. Insulation will save energy and provide a healthier, more comfortable environment. Most heat is lost through the ceiling (42%), the rest through windows (12%), cracks (12%), or the floor (10%).

Don't let engineers over-specify HVAC equipment

  • Conservative approaches often lead to 30% excess capacity in HVAC plant, which creates enormous ongoing inefficiencies. Ask your engineers how they decided on the HVAC plant size and test their assumptions.
  • If possible, retain existing systems or ductwork but ensure all air ductwork is cleaned to remove dust, dirt and mould before occupation.

Don't skip commissioning

  • Time over-runs may mean essential testing and balancing of the HVAC is not done until the building is occupied. This can lead to an unbalanced and inefficient HVAC system.
  • A building needs to be 'tuned' over a full year's running to ensure all systems are operating properly in all climatic conditions.

Look after HVAC systems

  • Ensure you have a building users' guide for the engineering systems.
  • Your HVAC system must be designed, operated and maintained to a required standard or it may cause air pollution as a result of poor maintenance.
  • Set thermostats, with adjustable dead bands, between 20-24oC.
  • Avoid after-hours use of the HVAC system. Find out how the HVAC system is zoned. Ensure that after-hours switches service an area not greater than 500m2 and that they automatically switch off the HVAC system after a pre-set time.
  • Avoid using single heaters as much as possible. If you have heaters use radiant heaters, not fan heaters.
  • Have your HVAC system serviced regularly.

Useful resources and information

Although there is presently little New Zealand based information available about efficient HVAC systems, the Energy Efficiency and Conservation Authority has produced a local case study (Wellington District Court) highlighting one of the countries most energy efficient air conditioned buildings. The case study [PDF, 440 KB] is available on the EMProve website.

Case study: heating, ventilation and air conditioning (HVAC)

Improved building design with good insulation, natural ventilation and an optimised glazing-to-wall ratio can reduce the need for air conditioning. The Landcare Research building in Tamaki, Auckland is an example of this, with climate control used only in specific areas with functional requirements such as preserving specimens or meeting biological containment requirements.

As for many public service agencies considering leasing office space, the footprint and design of Environment House were already established, so the Ministry had to consider what sort of HVAC system would best deal with the specific issues it faced, including:

  • the desire for a highly energy-efficient system
  • the lack of natural ventilation - no opening windows
  • the need to service a large meeting room.

A Variable Air Volume (VAV) system was originally proposed for the building. These are common in office buildings, and modern systems can be reasonably efficient. However, they need considerable exterior plant space, unless space has been allowed for within the building.

Variable Refrigerant Volume (VRV) systems use reverse heat-cycle heat pumps and offer flexibility for customising air conditioning to meet the requirements of different areas. They also allow scope for optimising energy-efficient operation, in particular through heat recovery, and need less outdoor space than VAV systems.

The VRV system installed in Environment House allows for heat exchange to occur between areas needing heating and those needing cooling, improving its energy efficiency.

The choice of refrigerant is also important. Refrigerants can be ozone-depleting and add to global warming. The refrigerant in the installed system (R410A) is a zero ozone-depleting refrigerant and therefore the most environmentally friendly available.

  • Install a building management system.
  • Select options that are as energy efficient as possible.

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