scene of fresh air at oceanThe University of Queensland operates a comprehensive energy efficient HVAC program across campus to continually reduce energy consumption.

The proportion of total energy consumption varies from building to building but is typically around 40-60 per cent of total electricity usage.

UQ is improving the energy efficiency of air conditioning (AC) systems by repairing, enhancing or replacing older systems and educating building occupants on the best way to manage their workspaces. 

Think globally and act locally. The following simple actions can make a big difference in the University’s overall environmental footprint.

  • Keep doors and windows closed in air-conditioned spaces
  • Use air conditioning only when required
  • Do not place heat loads near temperature sensors
  • Be realistic about what air conditioning systems can achieve
  • Dress appropriately for the season
  • Use a fan to cool down
  • Avoid using personal heaters in air-conditioned spaces

1. Keep doors and windows closed in air-conditioned spaces

Leaving doors or windows open or ajar requires the AC system to work harder to maintain the temperature setting and results in large energy inefficiencies.

Myth

AC systems recycle air already within the building and occupants are breathing old, stale air.

 

Result

This myth can lead people to open windows and doors in an effort to introduce fresh air, but this is counter-productive and wasteful. Air conditioning slightly pressurises rooms so that when windows are opened cool air flows out and negligible outside air flows in. The AC system has to make up for the excessive loss of cooled air and may struggle to maintain the set temperature, wasting energy.

 

Reality

Codes require that central air conditioning systems continuously bring in a specified amount of outside air to displace air in circulation. This outside air is filtered before it is cooled, dehumidified and ducted to occupants. P&F is retrofitting systems to bring in larger amounts of outside air than codes require, when the outside air is at a comfortable temperature.  

 

Action

Keep all windows and doors closed in air-conditioned spaces to save energy. Even small openings can lead to big inefficiencies. If you notice any leaky windows or doors, please report them to pfassist@pf.uq.edu.au

2. Use air conditioning only when required

AC should only be operating during typical business hours (7am – 6pm, five days per week) unless required for a specific purpose, e.g. to keep a constant temperature in a laboratory. Accommodating occasional work outside business hours is best achieved with the use of after-hours activation buttons.

Myth

Leaving AC on overnight reduces energy costs as the building stays at the required temperature and the need to cool a hot building is avoided the following day.
 

Result

Leaving the system running at all times results in an energy use increase of more than 250 per cent above typical business hours operation.
 

Reality

The normal schedule starts AC during the coolest time of the day. It only takes a fraction of the energy to bring the space to the set temperature at around 7am compared with the energy to keep the space cool overnight.

Action

Turn manually controlled systems such as split systems off before leaving the office at the end of each day. If you believe your workspace AC is operating outside normal business hours without reason, or if installing an after-hours button may eliminate the need for 24-hour operation, please contact pfassist@pf.uq.edu.au.

Cooling the air once the AC is activated typically takes no more than 15 minutes. During this short time, period tower fans can be useful (see tip 6).

3. Do not place heat loads near temperature sensors

Ensure temperature sensors are away from heat sources such as photocopiers, computers, fridges.

Temperature sensors are small, off-white to taupe coloured boxes set on a wall at approximately chest height (sometimes labelled ‘Johnson Controls’). They measure the average temperature in a room to provide feedback to the AC system.

If temperature sensors are confused by other heat sources, the AC system will work harder, making the air uncomfortable for occupants and wasting energy.

4. Be realistic about what air conditioning systems can achieve

Only in limited circumstances can AC achieve tight control of the temperature and humidity in a space. UQ office and teaching spaces are maintained between 21 and 24 degrees Celcius. Temperatures start towards the bottom of the range at 7 am and rise by mid-morning to the top of the range as people arrive and equipment is running. For the rest of the time they remain reasonably stable, unless there is a dramatic change in weather.

The normal fluctuations of a few degrees in work space temperatures may not be noticed by some people and can be accommodated by others by making slight clothing adjustments (see tip 5 ) or by using a fan (see tip 6). On very hot days with temperatures above 32 degrees Celcius AC systems will come under stress and may struggle to maintain workspace temperatures.

5. Dress appropriately for the season

Reduce your reliance on artificial heating and cooling by dressing appropriately for the season and expected weather. Wear a jumper or jacket in winter and shorts or a skirt in summer. Very small adjustments to clothing can make a big difference.

6. Use a fan to cool down

A fan uses a tenth of the electricity used by an air conditioner. If you can, use a fan instead of an air conditioner to keep cool. Fans are very useful to supplement AC on very hot days when systems struggle to maintain conditions. Medium height tower fans will keep you cool without blowing reports and notes off your desk.

Fans are especially useful when:

  • You come back into the office and need to cool down after being outside.
  • You find the AC set point in your workspace to be too warm, particularly if other occupants are serviced by the same AC system and may be disrupted by a change in the default temperature.
  • You come into the office after hours, instead of using the after-hours AC activation button.

7.  Avoid using personal heaters

On cooler days some occupants may be tempted to use personal heaters in air-conditioned spaces. Heaters can be an OHS issue and play havoc with air conditioning especially if they are near temperature sensors.

In Brisbane, even on a winter’s day, the AC system may be working from mid-morning onwards to cool the office and personal heaters just add further to this load.