As one would expect, Australia has numerous climate zones. These zones require different design strategies to achieve good energy efficiency. We operate in other states also but I will limit this post to design strategies specifically for Perth. At the start of the design process, it is crucial to obtain climatic data for the region. Elements such as air temperature, heating and cooling degree hours, solar irradiation, humidity, rainfall, and wind, impact the design elements of a dwelling. This data will assist in developing design strategies that will contribute to the energy efficiency of a dwelling in a specific location.
Daily Temperature Range
In Perth, the daily air temperature range is quite large. This, in turn, means that thermal mass can be used to advantage to stabilise the inside temperature.
Heating and cooling degree hours
Heating and cooling degree hours is a measurement of temperature, combined with hours. It shows the amount of time that the outside temperature is either hotter or colder than the comfortable range.
In Perth the summers are quite hot and long and winter has a good amount of radiation from the sun. This would mean that the natural heating of thermal mass in winter and good cross ventilation in summer are very important.
Solar irradiation is a measurement of the number of clear days in a year. Perth has a high number of clear days which means that especially in summer it is important to shield the sun from entering the home. This would be done by carefully considering orientation, limiting west and east windows, using appropriate eave design to allow in low angle sun (winter), and last but not least providing outdoor living that is fully shaded in the summer months.
Humidity impacts the feeling of comfort in conjunction with the ambient temperature. Hence it is important to have openings facing the cooling breezes. Utilising larger openings on the opposite elevation to facilitate good air flow. It is equally important to provide clear pathways for cross ventilation of every habitable room.
Considering the mean rainy days in Perth, most effective rainfall is limited to 3 months of the year. Hence sizable tank storage is important to carry the occupants through the dry months. Additionally, designing for greywater recycling makes sense.
The Bureau of Meteorology also provides wind diagrams. they show strength and direction of winds at certain times of the day. This provides key knowledge in the orientation of windows to allow for effective use of cooling breezes. It is also beneficial to shield the interior from cold winter winds. In Perth, the cooling breezes come from southwesterly winds during the afternoons. These winds are also affectionately known as the “Fremantle Doctor”.
Using cross ventilation to flush the heat from a dwelling during the night is very effective as well as using stack cooling, especially in double storey applications. This uses opening roof windows the flush hot air that naturally rises.
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