Passive Solar Design principles don’t just apply to new housing. These important principles should also be considered and applied every time we renovate. There are very good reasons for doing so and the Spring Hill "Enviro-Cottage" Project tries to demonstrate ways in which this can be done.
Australia’s housing stock accounts for 20-30% of national energy use. Of that, up to 50-70% is used to heat water and heat and cool the house itself. In Brisbane average daily energy use per person continues to increase. The increasingly standard practise over recent years of installing air conditioning into our houses has a lot to do with that (is this because of global warming or is it lifestyle choice?). Air conditioning has traditionally been used in Brisbane as a selling point for a home. How would this compare to a house designed so well for Brisbane’s climate that air conditioning or heating is simply not required and running costs would therefore be that much lower?
Passive solar design is primarily about energy and comfort. It simply means heating, lighting and cooling your home using directly and indirectly the sun’s heat and light. It is about designing to allow the structures of the home itself to collect, store and redistribute heat.
The building itself is used to trap and store the heat from the sun to warm the home in winter (occasionally needed in Brisbane) as well as stop the sun from heating the house and encouraging cooling air movement in summer. Passive solar design will provide for a naturally comfortable building and healthy living space while saving on heating, cooling, ventilation and lighting energy costs – good for you and good for the environment.
When considered at the planning stage, passive design elements should add little or no additional cost to building or renovating a home, and think of the money to be saved on the air conditioning bill.
Local climatic conditions, such as the sun’s changing movements through the day and across the seasons, prevailing winds, temperatures and humidity must be considered. Brisbane’s climate allows a home to be comfortable all year without the need for additional mechanical cooling or heating.
To deliver a passive solar design for Brisbane’s climate:
- house orientation for northern solar aspect (face living areas to the north) and for exposure to cooling breezes,
- use of thermal mass such as concrete floors and brick walls to store and redistribute heat in winter and extract heat from rooms in summer,
- natural ventilation and use of ceiling fans where required,
- minimise building depth and maximise external wall areas to encourage movement of cooling breezes through the building (cross ventilation),
- window and awning size and orientation. North facing windows should be large to permit solar access in winter to avoid the need for additional heating systems. These windows must be shaded in summer by use of eaves or a verandah. South facing windows should be small and east and west facing windows should be well shaded.
- selection of light coloured roofing and wall materials to reflect heat,
- use of shading wherever possible in summer and particularly east and west walls and glass windows and doors all year round (unprotected glass can be the single biggest source of heat gain in an otherwise well insulated home),
- use of natural lighting,
- use of bulk and reflective insulation in ceilings, walls and floors to keep warmth in in winter and heat out during summer,
- sealing gaps to stop draughts, and
- landscaping including provision of screened and shaded outdoor living areas.
When renovating, these same principles can be addressed and worked to your advantage. Look for ways to use thermal mass effectively, increase solar access in winter, improve insulation performance, ensure new windows are designed effectively and existing windows are enhanced with awnings or other shade devices where required, upgrade glazing where required to improve performance, close gaps and door seals etc, add pelmets and update curtains and drapes if required and look to add roof vents. With a large renovation you may also look for opportunities to move whole rooms around in your design to ensure living areas are exposed to the north aspect.
Every home and block of land, and every renovation situation is unique so always consider using an architect or designer experienced in designing for Brisbane’s climate to help drive maximum benefit from your renovation effort.
Read how the Spring Hill "Enviro-Cottage" uses passive solar design.
