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Passive Solar Design Principles

How do I… design using passive solar design principles?
With increasing concern for the environment and rising energy bills, a lot of people want to incorporate passive design principles into new homes, or green-ovate by retrofitting passive design features into existing properties. Passive design is all about taking a commonsense approach by creating a home that adapts with the seasons, one that is comfortably warm in winter without feeling like an oven in summer. It needs to be appropriate for the climate, oriented to take advantage of the natural warming and cooling attributes of the site, and use the right amounts of insulation in the roof and walls glazing and thermal mass to ensure year-round comfort. Well-positioned windows will allow ventilation in the warmer months, while cladding the exterior of the home with lightweight materials will also make it easier to insulate, and will stop it from overheating in summer.

Position, position
Correctly orienting your home involves positioning or renovating a home to take advantage of the sun in winter, and cooling breezes in summer. According to the government’s Your Home Technical Manual, the first step to prioritise your heating and cooling requirements. In hot humid climates or hot dry climates where winter heating isn’t required, you should aim to exclude the sun year round by shading and maximising exposure to cooling breezes. In all other climates, however, a combination of passive solar heating and passive cooling is required, although this will vary with climate.
“There is no one size fits all approach to passive design,” says Professor Richard Hyde, author of Climate Responsive Design and Professor of Architectural Science at the University of Sydney.”It can also be quite a challenge to retrofit a house, and success can depend on climate and the home’s orientation.”
He advocates using experts to provide micro-climate analysis of a site that assesses the angle and direction of the sun throughout the year, wind speed and direction and considers other factors like humidity that help determine the best orientation for the house. The way the building will be used also needs to be taken into consideration when planning how to use energy more effectively.
“It’s important to take a ‘whole building’ approach and consider how the elements will work together,” he says, adding that when it comes to ‘green-ovating’ you need to work out which things can be changed, and which will only cause more problems.
“For example, if you increase the amount of insulation in a poorly ventilated house, it will only make keeping it cool in summer a bigger problem, unless that problem is sorted out too [by changing the number, style or location of windows].”

Warmth from the sun
A good place to start green-ovating, he says, is to identify a north-facing room that can be used as a solar collector in winter. Windows facing north receive the sun for the longest part of the day in winter, and when the sun is high in summer, eaves and other forms of shading will help ensure the sun doesn’t penetrate.
“Using the heat gained through the windows in combination with thermal mass” – strategically positioned concrete or brick inside the home (such as a floor or wall) that is able to soak up heat during the day and release it in the evening when it’s cooler – “will make the home more resilient and less reliant on fossil fuels for heating,” Professor Hyde adds. “In cooler climates, for example, people often add a conservatory onto the building to collect the sun’s warmth and heat the air.”
If renovating, and the front of your block faces south, consider placing living areas where the family spends the most time at the north-facing rear of the home. If there block faces east or west, place living areas towards the rear facing north, while if the front of the block faces north place them at the front. Windows are the weakest link in a home: too much glass on the eastern and western sides of the home allows the sun to penetrate in summer and can cause the house to overheat, while in winter too much heat can be lost through large glazed areas, especially those facing south. Using skylights instead of traditional windows to allow light to penetrate dark areas of the home, and installing heavy curtains to reduce heat loss in winter, can help balance the heat budget. In the summer months, however, free cooling is easily achieved by using cross-ventilation and by having shaded windows that open fully – where windows are open on both sides of a room or house, air can flow freely across the space and cool it.
“As energy costs escalate and concerns about climate change continue to mount it’s just intuitive that we will see more and more people using passive design principles to warm and cool their homes,” says Professor Hyde.

This article was originally published on the Light Home Magazine Website, an informative hub for designers, builders and renovators who have discovered the benefits of using light weight, sustainable building materials.

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