Heating and cooling
If your building has a central heating and cooling system then you could make significant energy savings.
Heating and cooling projects
Heating and cooling systems in large buildings are often referred to as 'Heating, Ventilation and Air Conditioning' systems, or HVAC.
The central heating and cooling systems in high rise apartment buildings are often comprised of centralised water loop systems, cooling towers, fans and water circulation pumps.
In smaller apartment buildings you may find ‘package’ units that duct the conditioned air around the building or even individual ‘split’ system conditioning common areas.
Strategies to save energy on heating and cooling.
Tune time controls and temperatures
- Engage a HVAC maintenance contractor to regularly maintain and inspect your system
- Select realistic operating hours - every extra hour per day of operation represents around 7 per cent of additional air-conditioning energy
- Install timers on air conditioners
- Upgrade older ‘split systems’ to those with a high ‘star rating’
- Widen the temperature band where no heating or cooling will occur – a cooling temperature of 25°C and a heating temperature of 18°C can reduce energy use by 20 per cent compared to a 20°C - 23°C control band
- When the temperature outside is in the required comfort band, it is often possible to cool buildings using outside air - check to see if your system can operate in this way
- Install CO2 monitoring to control fresh air intake to meet occupancy requirements, thus only heating/cooling the amount of outside air required
- Install variable-speed drives on pumps and fans
One of the best ways to save money on energy bills is to insulate a building. Insulation acts like a barrier, preventing heat passing in and out of the building. By reducing heat flow you can maintain a comfortable temperature inside, regardless of the temperature outside.
In winter, once the building has been heated to a comfortable level, it will stay that way with less energy input compared to an uninsulated building. In summer the insulated building will take longer to heat up, and air conditioners will need less energy for cooling.
There are two main types of insulation:
- Bulk insulation comes in many shapes, thicknesses and materials and is primarily used in ceilings and sometimes in walls. Bulk insulation stops heat flow by trapping air in small air pockets.
- Reflective insulation resists radiant heat by reflecting or not emitting heat. It is usually shiny aluminium foil laminated onto paper or plastic and requires a layer of air between its shiny reflective side and the roof or wall cladding.
The type and level of insulation you need for your building depends on where you live, the building materials used, and whether you will be using additional heating or cooling. When installing, make sure there are no gaps as this decreases the effectiveness. Particular care should be taken around halogen downlights in ceilings.
Finally, when choosing insulation compare the environmental benefits of different products, along with how much of the product is made from recycled materials and how easily the product can be recycled. For example, some products are made from 80 per cent recycled plastic drink bottles or 100 per cent recycled paper.
All buildings have air leaks or draughts. Draughts and unwanted air leaks not only make your home uncomfortable, but they can also increase heating costs by around 20%.
Draught proofing involves finding and sealing those draughts that let the cold air in and the warm air out in winter to make the building more comfortable and energy efficient. You can check for draughts by:
- Looking for obvious gaps – visible light under and around doors and windows;
- Listening for rattles or whistling around doors and windows, especially during strong winds;
- Feeling for moving air around doors, windows, vents, stairways, floorboards, built-in heaters and air conditioners, architraves, and skirting boards; and
- Looking for movement in curtains.
Special care needs to be taken in houses which have internal gas appliances, especially houses which have flue-less gas heaters or an open flued gas heater. If you undertake draught sealing and you have indoor gas appliances, you should get a licensed gas fitter to check the safe operation of the appliances before they are used.
Poorly planned or wrongly sized windows can either let in unwanted heat, or hamper the flow of fresh air into a building. However, thanks to some clever new technologies, windows no longer have to be a compromise between getting enough light and keeping the building at a comfortable temperature. Some types of glass can help make windows more energy efficient.
- Tinted or toned glass is coloured glass that acts like sunglasses to reduce the amount of heat and light entering a building.
- Reflective glass has a coating that reflects heat and light away from the window.
- Double-glazed windows are window units with two panes of glass and a sealed air gap in between. These are far superior to single-glazed windows for insulating a building.
- Low-emissive (low-e) glazing is a glass coating that blocks radiant heat transfer (heat waves given off by hot objects). It acts like a 'heat mirror', reflecting heat back into a room in winter, while letting sunlight in from outside.
To help you make the right choice, the Window Energy Rating scheme (WERS) rates the energy performance of windows and gives them a star rating according to their heating and cooling performance. Look for the WERS label when selecting a window and choose the window with the highest star rating for your climate and budget.
Cooling towers can be part of a large apartment building’s air conditioning system. They are used to reject heat from the HVAC cooling water by evaporation. Energy is used to pump water through them, and every drop of water pumped around a building has an associated energy cost.
If you have cooling towers installed close to boilers then you could install a heat exchanger to use the heat from the condensers (going into the cooling towers) to pre-heat the water going into central hot water heaters. This will also reduce the load on the both the boilers and cooling tower. You will need to consult a professional engineer around a project relating to cooling towers.
* Facilities Management, Good Practice Guide, Multi Unit Residential, Facility Management Association of Australia.