| National design handbook prototype on passive solar heating and natural cooling of buildings |
|II. The Australian climates and people|
Australian climates differ from those of Europe and North America (from where most of the available literature on passive solar design comes) in that for much of the year the diurnal ambient temperature range moves in and out of the accepted comfort range. Generally, In summer maximum temperatures are above the comfort zone whilst in winter the minimums are below. For many locations, comfort conditions are not achieved outside during winter at any time of the day. The problem of comfort in some locations such as Sydney, Adelaide, Perth, Canberra and Brisbane has to do with summer overheating whilst in others such as Hobart it is more one of underheating in winter.
Locations such as Canberra, the country's capital, are both cold in winter and very hot in summer. Winters are more sunny than those of Northern Europe and so solar energy can play an important role in reducing domestic energy consumption. It has been shown In many studies that passive solar design and energy-conservation techniques are very cost-effective in Australia. These climates allow enjoyment of the outdoors generally throughout the year except on days of temperature extremes. This, along with the relatively low cost of energy in the domestic sector, has contributed to a lack of concern about energy matters.
The Australian continent (see figure 12) can be described generally as having an arid central region with a border of tropical, monsoon climate in the north and a predominantly Mediterranean climate with hot dry summers and cool to mild, wet winters in the south. The eastern coastal strip and adjoining uplands have a more evenly distributed rainfall. In northern New South Wales and along the Queensland coast the climate is moist tropical whilst along the coast of southern New South Wales, Victoria and Tasmania it is generally classified as moist temperate. The mountain ranges and tablelands along the east coast could be described as cool temperate.
It is always difficult to relate the general meteorological description of a country's climates to that of climatic characteristics for thermal comfort in buildings. The general description is usually intended to cover the agricultural aspects, and is quite inadequate for building-design purposes.
This guideline document will address the design parameters for three general climatic types in chapter V.
The hot arid climates. to some extent, also includes the dry summer climate of the southern coast (Mediterranean style). These areas are characterized by hot, low-humidity summers and cool to chilly but generally sunny winters. In the central arid zone summer temperatures are generally very high (35-40C during the day) with cooler night-time conditions and varying breezes (usually approximately 20-25C).
The cool temperate climates are those where the winters are cold and the need for heating is far greater than the need for cooling in summer. Tasmania and many locations in the southern and northern tablelands of New South Wales are locations with such a climate. The major design consideration in such a climate will usually be winter heating. In summer the concern is to avoid overheating by good design. Cooling should not be an issue as the daytime ambient temperature is normally in the desired temperature range for thermal comfort (less than 27C).
The hot humid climates in Australia are characterized by high humidity levels in the wet season and the lack of a heating season. The strategies for good climate design are quite different from those suited to the other climate zones.
The three climate categories described are an over- simplification of the specific local climates that can be found throughout Australia. They are, however, adequate to describe the basic approach to design for passive solar heating and natural cooling of small-scale buildings. Some of the more detailed aspects of climate will be addressed with the specific design strategies and details where appropriate in the text. An excellent and extensive source of climate data for building-design purposes has been prepared by Szokolay and is available through RAIA bookshops, ARCHITEXT.
Australian houses are generally larger than one might expect to find in Europe, the average area being 120 to 140 m. In recent years Australians tended to follow more the American model of open-plan living and clear visual connection to the outside. This has produced houses that are energy-inefficient, with glazing oriented with little regard for the sun's movement, despite the resultant overheating effects that occur in summer. and the lost opportunities provided by generally sunny winters.
Although most people consider Australia to be a warm sunny place, many of its centres of population are very cold in winter (Canberra 2270 heating degree days and Melbourne 1500 heating degree days ). About 14 per cent of all primary energy and about 50 per cent of all electricity generated is used in the domestic sector. Rising expectations for standards of living are resulting in a growth in per capita energy use while peak energy demand is also growing. particularly through the increasing use of air conditioning. In Melbourne approximately 50 per cent of energy used in the domestic sector is used for space heating and cooling. In New South Wales, the state with the largest population, 45 per cent of all electricity is used in the domestic sector. The result is that issues affecting the consumption of electricity (either up or down) become very politically sensitive. Australia relies mostly on coal-fired thermal generating plants for electricity due to the abundant coal supplies.
Figure 13 shows the relative severity of the climate of the major population centres and approximate per capita energy consumption in the domestic sector. About 70 per cent of Australia's population lives in urban centres with 60 per cent living in five of the main cities or their satellites, Sydney, Melbourne, Adelaide, Hobart and Canberra. All of these cities have a significant heating and cooling load by Australian standards.
The results of surveys conducted to determine public attitudes to energy conservation. show that saving energy Is perceived to be a reduction in standards and not an action to aspire to. Yet. it has been found that people always seek higher standards of comfort. If this can be achieved at no increase in running costs or even a reduction in running costs, then it is desired. The problem then is to market these ideas to the home-buying public.
Unlike most other developed countries of the world, there are no regulations relating to energy conservation such as mandatory insulation levels in Australia. An attempt was made a few years ago to introduce regulations requiring very moderate levels (R1.0 m K/W) of insulation to ceilings of all new houses in Tasmania, the coldest and most southern state of Australia. This was thwarted by a state government election. At present, there is a draft code In Victoria which many hope will be presented to Parliament in the near future. The proposal, if adopted in full, would require that all new houses be built with a minimum of R2.0 m K/W added resistance in the ceiling and R 1.0 m K/W added resistance in the walls. There is a strong feeling that there should not be regulatory controls over the use of insulation, due to the increased costs that would be Imposed on building costs. In spite of the lack of regulation, ceiling insulation is used widely in most states. Wall insulation is being introduced gradually and some project builders (builders of standard-design houses) are now offering full insulation of ceilings and walls as a bonus in their sales package.