Is it possible to have a home that is naturally well-lit and ventilated, and makes the most of the local climate to maintain a consistent temperature all year round?
If you’re lucky enough to be building a new home, the answer is yes!
Climate-sensible building technologies such as Passive Solar Design harness natural energy flows to make your home more comfortable to live in and cheaper to run.
It’s all in the name: Passive because it is guided by external influences. Solar because it uses free energy from the sun, and Design because it’s planned and integrated into your home design.
The result is an energy-efficient, comfortable home – with lighting, heating, and cooling complements of Mother Nature! Here’s how it works:
The secret to successful Passive Solar Design is getting the orientation of your house, windows, and any glass doors, right in relation to the sun. Read
our guide to Window Planning.
In all but Tropical climates, for maximum efficiency, your home should be built along an East-West axis, with the longest side facing due North. Don’t worry if your building block doesn’t allow you to get this spot on, you can be up to 30º off-axis and still be over 90% efficient.
Have you noticed how the sun is lower in the sky in Winter and almost overhead in Summer?
As you can see from our diagram above, in the southern hemisphere, the sun travels in a low arc across the winter sky and reaches its zenith in Summer. That’s why in Summer, most of the heat enters your home through your roof, and your East and West-facing walls.
In contrast, North facing walls get most of the sunlight in Winter, and South facing windows lose heat. The good news is that you can take advantage of all this natural energy.
In Winter you can use large Sashless Windows to bring low-angled sunlight into your home to heat it for free. Sashless windows slide up and down in the same way as a double hung window, but they have no aluminium frame to obstruct the view or light.
You can easily shade your windows in Summer with horizontal shades, like eaves, awnings, and pergolas because the sun is almost directly overhead. Preventing the sun streaming in can make your home up to 90% cooler naturally and help your air-con to work much more efficiently.
If you have an amazing view or want to make the most of your connection to the outdoors – large glass
doors and windows may be the way to go. However, one of the biggest mistakes people make with Passive Solar Design is calculating the size of windows.
Image: Camelot Homes
North-facing windows receive twice the sun than East and West facing windows. If you make your North-facing windows too grand, you could end up with too much heat gain in Spring and Autumn.
Fortunately, you can calculate the size of your windows as a percentage of the total space that the window will heat. The percentage used in the calculation varies depending on your climate region, but as a rule of thumb, the glazing area should be between 10% and 25% of the floor space of the room.
So, size does matter – but consider this as well:
East and West-facing windows receive very little sunlight in winter, autumn and spring, but are the biggest source of heat gain in Summer – particularly Western windows, which cop the harsh afternoon sun streaming in at a low angle.
East facing windows are not quite as bad because they receive morning sun at the coolest time of day. They are perfectly positioned for greeting the morning light and improving air movement.
Windows on both these sides of the house should be kept relatively small. You can shade them with shutters, overhead awnings or some well-placed trees. Alternatively, you could use high performance glazing such as Viridian Low E or VFloat™ Toned glass, or specify double glazed windows which provides even greater thermal control.
South-facing windows don’t contribute to heat gain and can provide soft, even light that’s perfect for workspaces and bedrooms. As cooling breezes generally come from the South in summer, windows facing this way also help with cross ventilation.
No shading is needed for South facing windows, so you can capture as much of your view as you like.
Sleek, low profile Wideline Sliding Windows, or Awning WIndows would work a treat. But don’t go too large – South-facing windows can also lose a lot of heat in the Winter. Maybe include energy efficient glass such as Viridian ComfortPlus™ Low E Glass, to retain the heat and your view.
The amount of sun your windows and doors get depends on the time of year. Ideally, North facing windows should receive an unobstructed view of the sun
from 9 am to 3 pm.
Image: Gartner Rose
But sometimes, even the best building block won’t allow this. So how do you make the most of your orientation? Here are some ideas:
Image: Three Birds Renovations
Building a new home is an amazing opportunity to shape it the way you want.
With careful planning and siting, you can create a home that saves energy and is naturally comfortable all the time.
If you are wondering which windows and doors will work best in the Passive Solar Design of your new home or renovation, talk to a Wideline consultant. Together you’ll be creating a home that helps you thrive.