Passive design
Most Queensland homes with air-conditioners run them for around 600 hours a year, at a cost of more than $1200 per unit over a typical 12-year lifespan, and causing the emission of up to 12 tonnes of greenhouse gas.
Passive design is design that does not require mechanical heating or cooling. It is about making the most of local conditions to make your home comfortable, affordable and sustainable.
By paying close attention to all of the aspects below, you can reduce heat entering your home by up to 90 percent:
- insulate ceilings, walls and floors
- seal off draughts around windows, doors and any other gaps
- provide external shading to north, east and west windows
- create ventilation to allow cool outside air into the house
Incorporating passive design in your home saves you money, increases your comfort and reduces greenhouse gas emissions from heating and cooling. A high energy conservation rating also adds to the overall value of your property at resale time.
Getting the most out of passive home design
‘Building envelope’ is a term used to describe the roof, walls, windows, floors and internal walls of a home. Its performance in modifying or filtering climatic extremes is greatly improved by passive design.
Well-designed envelopes maximise cooling air movement and exclude sun in summer. In winter, they trap and store heat from the sun and minimise heat loss to the external environment.
Good passive design uses natural heat from the sun and natural cooling to keep your home comfortable. Cross ventilation allows natural airflow to cool your home. Ceiling fans can boost air flow using far less power than air-conditioners. And if you live in a hot and dry climate, an evaporative air cooler may be a cheaper alternative than an air conditioner.
Insulation can help reduce heating and cooling bills.
Passive design also means designing your home for your climate. In tropical areas, lightweight materials, shade and ventilation help keep your home cool.
In areas where there is a big difference between day and night temperatures, smart use of dense building materials allows the absorption and release of heat to improve comfort within your home.
Windows are also a key to passive design. Orientation, size, shape, glazing and shading of windows make a big impact on the heating and cooling of your home.
How to create a passive design for a cooler home
Most of Queensland is in sub-tropical or tropical latitudes. Most homes use more energy for cooling than heating.
The main elements of design to achieve passive cooling are:
- Orientate the building for exposure to cooling breezes.
- Increase natural ventilation by reducing barriers to air paths through the building. Open up enclosed verandahs and don’t enclose subfloor areas.
- Install a roof ventilator.
- Provide fans to move air in the absence of breezes.
- Choose appropriate windows and glazing to minimise unwanted heat gains and maximise ventilation.
- Provide effective shading (including planting trees). Use blinds or screens on verandahs to block sunlight but allow ventilation. Use heavy curtains or blinds to reduce heat transfer through windows particularly on western elevation.
- Ensure adequate levels of appropriate insulation are installed.
- Choose high thermal mass construction in regions with significant day and night temperature ranges (and low thermal mass construction in regions with a narrower temperature range).
- Use light-coloured roof and wall finishes to reflect more solar radiation and reduce heat gain. Several manufacturers now make heat-reflecting roof coatings that claim up to a 20 percent reduction in ceiling temperatures.
Colour plays a bigger part in how cool you feel than you might think. Colour has an important impact on our mood as well as affecting our perception of the temperature.
In rooms of the same temperature, people perceive it to be cooler in blue coloured rooms than they do in red rooms. Blue rooms can also decrease blood pressure and create a passive, restful and subdued mood.
Painting rooms blue or other cool colours such as green, or incorporating objects that are these colours into your home can help you feel not only cooler but calmer as well.
Another important aspect of colour is that very light colours reflect more light than darker colours and so reduce the time you need to turn the lights on during the day.
