Keep your home cool with passive cooling
Stay chilled this summer with eco and budget-friendly design ideas that harness shade and natural breezes.
Bunnings magazine, January/February 2020
Prevention is better than cure, so your best bet is to prevent your home from heating up too much in the first place. There are plenty of clever ways to get passive cooling on your side; it’s all about working smarter, not harder, with clever features that will lighten the load on your hip pocket and the environment, while making your home naturally more comfortable.
What is passive cooling?
Passive cooling is all about strategically using shade, reflective surfaces and natural airflow to keep your home comfy. Most of the big decisions around this take place during the design stage, involving your home’s orientation and layout, and clever positioning of windows and ventilation products. Even choosing light-coloured exterior finishes, especially on the roof, can reflect a great deal of heat.
While you wouldn’t reclad your roof just to improve its energy profile, principles of passive cooling could guide your choice of finish or window position when planning an extension.
By the same token, if it’s time to repaint your weatherboards, choose a pale tone over a dark one. Adding a prefabricated pergola kit can be another reasonably low-cost upgrade; in the right location, it can significantly reduce the amount of wall area exposed to direct sunlight.
Seal the deal
Maximising shade on and around your house is a sure-fire way to a cooler home, but blocking all sun is neither possible nor desirable. That’s where insulation comes in.
“Glasswool insulation is great for keeping a house cool in summer and warm in winter,” says Claire Cunliffe, marketing manager for Earthwool. “When choosing the best product to use, look at the R-value, as this indicates how well the insulation performs at reducing heat transfer.
A general rule is the higher the R-value, the better the insulation will perform.” Insulation is particularly important in the roof space, as the roof is far harder to shade from the scorching sun than are walls.
When insulating your home don’t ignore your windows. “Make your home more airtight by insulating and sealing gaps to keep cool air in and hot air out,” says Stephen Procter, sustainable programs strategic delivery manager for the NSW Department of Planning, Industry and Environment.
Windows let in up to 10 times more heat than an equivalent section of insulated wall. Stephen suggests, “You can also help keep your home cool in summer by installing shading or by simply remembering to keep your blinds down and your doors and windows closed on hot days.”
Cellular blinds have a heat-reflecting interior lining and provide excellent insulation by trapping air inside their honeycomb structure. Tinted window film with a reflective mirror finish is another way to stay comfy, as it can block up to 98 per cent of ultraviolet rays and 89 per cent of heat transmitted as infra-red radiation.
Look outside the house for more clever cooling solutions. Outdoor blinds can effectively prevent heat and light from reaching a window or wall. Folding arm awnings and wall-mounted umbrellas are also brilliant at providing shade when you need it. For a more permanent solution, a shade sail can also block sunlight from a considerable section of wall.
Pool of talent
Evaporating water from an uncovered pool does help to lower the temperature of nearby air, and ponds and other water features can provide the same effect. Fountains and waterfalls speed up evaporation, too, chilling the air even more.
If you add a water feature to your outdoor space, position it near a window or door to create a zone of colder air that can easily flow inside. A pond in a shaded area near the window of a living space can also harness the power of convection for passive cooling; this means that, as warm air rises and escapes through windows in the upper areas of the house, cool air spills in to take its place.
Just bear in mind that with any body of water, you’ll need to abide by safety regulations, so always check with your local authority first.
Go with the flow
As the heat of the day fades, open windows to let air through. A gentle breeze can increase comfort, with a similar cooling effect to reducing the temperature by 3°C, as long as the humidity is 50 per cent or less.
Plantation shutters let you make the most of such airflow while still blocking sunlight. Stuart Hall, brand and digital marketing manager for EasyAS Shutters, says, “You can open the blades of EasyAS plantation shutters at any angle. This allows breezes to pass through while deflecting radiant heat and UV rays at the same time.”
For best effect, be aware of the prevailing wind and open windows on that side of the house. Also, to fully harness the benefits of convection cooling, allow hot air to escape through higher windows, skylights and roof vents.
Need help from mechanical cooling on the hottest days? In humid areas, an efficient reverse-cycle air conditioner is the best, but also the most power-hungry option. For a balance between comfortable cooling and minimum energy use, set it to 23°C.
“Standard air conditioners consume 3000–5000W on average,” says Jason Neophytou, HPM lifestyle expert. “To cool your home quickly, turn on the AC and ceiling fans at the same time. This rapidly distributes cold air, allowing you to turn off the air conditioning sooner and let the fans do the rest of the work.”
Looking for more ways to cool your home or outdoors? Check out some more of our cooling ideas and projects.
Photography credit: Brigid Arnott, iStock