We all want to save money on power bills and we do the right thing by the planet. But most of all, we just want to be able to survive our increasingly fierce Australian summers.
With record-breaking heatwaves all around the nation, staying cool and comfortable without having to run air-conditioning around the clock is our number one obsession.
We asked architect, urban designer and Certified Passive House Designer Andy Marlow for big and small ideas on how to make every home more liveable in the heat.
A director at Envirotecture and the Australian Passive House Association, Andy believes even tiny adjustments to how you cool your home this summer can have an impact on your next dreaded power bill.
“Every little change helps make you a little bit more comfortable, making you happier and reducing your need to use energy to be comfortable,” Andy says.
What is passive design?
“Passive design, also known as passive solar design, is when a building responds to its natural environment to make the indoor environment more comfortable,” Andy explains. “The important elements for summer comfort are shading, insulation, quality windows, thermal mass and cross-ventilation.”
If it sounds a bit old-fashioned or reminds you of grandma’s house with its big shady verandah and central hallway with doors open either end to catch the breeze, that’s because it is. “Historically all buildings responded to their natural environment as there was no alternative,” Andy says. “It’s only in recent decades that passive design slipped away as mechanical solutions dominated for climate control.”
How is passive design different to having a “passive house”?
“Passive solar design should not be confused with passive house (design),” Andy says. While they share many characteristics, a passive house is guaranteed to be completely sealed against the elements. "You can still open your windows if you wish,”Andy says, “but it’s airtight and comes with a heat recovery ventilation system to ensure fresh air 24/7.”
Why natural ventilation is key
Grandma was onto something leaving the doors open to let that breeze flow through the middle of her home. “Natural ventilation is your source of free cooling and fresh air so it’s your key to comfort and health,” Andy points out. “Ensuring your home can capture cooling breezes will keep air temperatures lower and also bring the cooling benefits from air movement much like a ceiling fan does.”
The power of insulation
“Insulation slows down the flow of heat so it’s the cheapest and easiest way to stay cool,” Andy says. “Heat flows from hot places (like the roof) to cooler places which means increasing insulation slows down the heat, keeping you cooler for longer.
“Controlling the flow of heat into and out of your building is critical to comfort and energy use. All surfaces facing the outside world should be insulated, with no gaps, to keep the interior surfaces of your home cooler.”
Once your home is protected from external heat, the aim is to keep it cool by closing windows and doors on the hottest days.
“In a well-designed home, this can keep you comfortable all day,” Andy says. “Then, by the time the heat makes it into your home the outside temperatures have dropped and you can use natural ventilation to cool your home. Simply keeping windows closed in the day and open at night, can lead to higher levels of comfort in many climates.”
Why ceiling fans really work
“You have to remember that air-conditioning cools air, whereas ceiling fans cool people,” Andy says. “That movement of air across your skin will make you feel 3-4ºC cooler and this can be much more pleasant than having an air-con unit blast cold air into your face. Ceiling fans are much cheaper to buy and run too.”
How does passive design make it possible to live without air-conditioning in the heat?
“A well-designed home will always be more comfortable than a poorly designed one,” Andy says. “But the temperatures at which passive solar design can work depends on the people who live their and their definition of comfort.”
Build a home that doesn’t require air-conditioning can mean thinking outside the box. “It’s possible to build an earth covered home if you wish to live in western New South Wales or Queensland and have no air- conditioning. This is the beauty of passive design, solutions exist they just need creativity and technical skills to make them a reality,” Andy explains.
How to apply passive design principles at your place
If you're building
“In a new build or renovation, achieving comfort through good design is quite straightforward for the experienced designer. Get the windows in the right location, shade them well and remember anything that is cheap, is cheap for a reason. Always invest in good windows as they are well worth it.”
At an existing property...
“Trying to keep heat out of the home by keeping everything closed up when it is hotter outside is the first step. If sun hits the glass of your windows, consider adding a shading device to reduce the heat load into your home. When the weather cools down to be cooler outside than in, open all the doors and windows to pull fresh, cool air in.”
If you’re renting...
“If you don’t have a ceiling fan and your landlord won’t install one, then get a pedestal fan. The movement of air will make you feel cooler and you can take it with you when you go. And if you don’t have external shading on sunny windows then using internal blinds on closed windows on the hottest days can be beneficial as you open them and the windows as the weather cools in the evening. Also, don’t forget that plants release moisture into the air which can have a cooling effect.”