Solar Passive Design

Simply stated this is the utilisation of sunlight to heat and light the living spaces within our homes without the use of mechanical or electrical devices, i.e. passive. A long understood but more recently forgotten technology that has the potential to dramatically reduce the energy costs needed to not only heat and light our homes but also reduce the amount of energy needed to cool them in summer.

The sun follows a predicted path across the sky that varies as the seasons progress through the year. The tilt of the planet during it’s circumnavigation around the sun produces a 28-degree swing either side of it’s rise in the east and it’s set in the west from midsummer to midwinter. This tilt also creates a change in the height of the sun in the sky at noon between these two solstice times.

In Perth the sun is around 81-degrees above the horizon in midsummer but sinks to only 34-degrees in midwinter. This 47-degree difference allows us, with appropriate shading, to keep the summer sun out of our northern windows in the summer whilst still allowing it in during the winter to provide free heating to our interior spaces. Shading at 69-degrees from the sills of openings protects them from solar heat gain coinciding with the hot season from late October to late-February.

The rising eastern sun and the setting evening sun in the west shine at very low angles to the horizon heating walls and rooms with windows without protection. These should be avoided wherever possible or shaded with structure or vegetation to stop this summer heat gain.

It can be seen from this that the layout of the rooms within a home and it’s orientation to the path of the sun in the sky is paramount in any design process and the simple reproduction of standard plan layouts without regard for solar principles is a recipe for the disaster of high energy costs over the full life of the building.