‘Solar passive design’ takes advantage of the climate to maintain a comfortable temperature range in the home & reduces or eliminates the need for auxiliary heating or cooling, which accounts for about 40% (or much more in some climates) of energy use in the average Australian home.
In solar passive design buildings, windows, walls, & floors are made to collect, store & distribute solar energy in the form of heat in the winter & reject solar heat in the summer. This is called ‘solar passive design’ because, unlike active solar heating systems, it does not involve the use of mechanical & electrical devices.
The key to designing a solar passive building is to consider how best to take advantage of the local climate & individual site characteristics by performing a site analysis. Elements to be considered include window placement & size, glazing type, thermal insulation, thermal mass & shading. Solar passive design techniques can be applied most easily to new buildings, while existing buildings can be adapted or retrofitted.
DESIGNING SOLAR PASSIVE
In winter, we take advantage of the sun travelling low in the northern sky, by building homes with windows facing north & inviting this sun in. In summer, when the sun is hot & high in the sky, we design overhangs to keep this sun out. Solar passive is very effective in Perth, because we have so many sunny winter days.
Once the sun’s warmth is indoors, we need to keep it there. We do this by having good thermal mass inside the house & good insulation wrapped around it. The thermal mass absorbs the energy, then slowly releases it, creating a warm comfortable space all day & night. Thermal mass is any material that can absorb a lot of heat, such as stone, concrete, bricks or water.
We make sure the house is well insulated, to keep that warmth inside. This has the same effect as wrapping yourself in a warm blanket. Examples of good insulation materials are timber stud framing filled with cellulose or rockwool, straw bales, hempcrete, or structural insulated (SIPs) panels. Bricks & steel are both poor insulators.
Low-E glass can be used for windows facing north as they allow light through, but not heat. This means that light comes in through your windows, is absorbed & converted to heat, & is then trapped inside. For windows on other walls, Low-E glass or double glazing can also assist in keeping your warmth in.
This image shows an effective way to use the incoming sunlight to warm your thermal mass & keep the room warm all day & all night.
Thermal mass also helps to keep your house cool in summer. By minimising the amount of energy coming in, the thermal mass will absorb it keeping the air at a comfortable temperature. This way the thermal mass acts as a temperature stabiliser.
So, what if your house position doesn’t allow you to face any windows to the North? No problem; we can let it in with a roof light. Using double glazed windows, with inbuilt block out blinds, we can let in the winter sun & keep out the hot summer rays. Roof lights are also great in summer, because you can open them to let the cool sea breeze flow through your house & blow out all the hot air.