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CLIMATE RESPONSIVE BUILDING DESIGN IN THE SOUTH AUSTRALIAN CONTEXT

Index

GENERAL

'South Australia' is a portion of the land area situated on the central southern coastline of the Australian continent. It is situated between the large continental land mass to the north and the large ocean mass and Antarctic to the south
As a result of solar inflow variation with latitude, in continental terms the large land mass to the north typically is warm, and the water mass to the south is perpetually cool. The interior continental land mass is arid, the summer winds flow over the substantial land area and are also warm. The ocean infiltrates cool air changes across South Australia in the general west to east flow of weather patterns
As a result the general weather patterns in South Australia are typified by cool winters with southwest winds and moisture, and hot summers with northerly winds, either dry and dusty, or tropical.

The climate is characterised as `temperate', with temperatures outside the normal human comfort range principally in summer. This is an arid fringe climate

PASSIVE SOLAR BUILDING DESIGN

Passive solar building design suits cool climates where inflow of solar heat gain creates comfortable interior space with limited additional interior space heating
This design approach has some applicability in the limited number of cool climate locations in South Australia

MICRO-CLIMATE BUILDING DESIGN

In arid fringe climate areas the design of buildings for comfort must address:- - resisting summer heat inflow from outside - ejecting the heat build up emanating from occupants and appliances inside the building
This approach is appropriate for comfort design for the majority of South Australia.

Climate responsive building design for South Australia is described in separate information sheets below about micro-climate, and building cross ventilation using heat, wind and moisture forces common in the arid fringe climate

THEORY DEVELOPMENT
Investigations about climate responsive building design in the South Australian context are the synthesis of:- - theoretical hypotheses - backed by empirical evidence - applied to building designs both in concept and real life applications.

The hypotheses used have been developed from basic meteorology and physics theory as described above.

Empirical evidence is available from human use of weather forces in other activities. In Australia about 1000 sailplanes achieve 150,000 flying hours in convection weather conditions annually. Convection weather conditions typify the forces available in the climate and are applicable to building design. This is one of the substantial empirical data bases available to the formulation of climate responsive building design principles.

Buildings designed to these climate responsive principles are in operation and are achieving the low energy comfort environments originally postulated.

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MICRO-CLIMATE FOR BUILDING COMFORT

THE WEATHER

Weather occurs everyday. Even though it varies in detail from day to day, it is nevertheless uniformly composed of three contributing influences:- - sun heating - wind - moisture mixed to varying degrees
These forces are the components pieces of micro-climate.

CREATING MICRO-CLIMATE

A standard vacant house block can be envisaged as consisting of flat and open ground, unfenced, and with neither structures nor vegetation on it. The climate on such featureless land is the same as that of the surrounding general area weather in which the site is located; that is - macroclimate and micro-climate are the same.

By erecting a building on that land, this changes the climate on the land. This occurs with every building constructed on every site. Now there is shade cast by the building onto the ground to the south of that building, and the portion of the site north of the building receives additional reflected heatload from the building's walls
By constructing a building on the land, the site is now segmented into a sun side hot zone and a shade side cool zone. This occurs as part of locating the building on the land. This is a simple example of the creation of micro-climate.

NATURALLY OCCURRING MICRO-CLIMATE

Very seldom is land as featureless as is described above. Existing features on vacant land contribute to modifying the climate on the site from the general area weather. Existing vegetation and structures on the land create shade and moisture variations; land slope and soils change the heating load on areas of the land.

On land with a north facing slope, compared with another with a south facing slope, quite different house designs will be required for comfort. Even where this land is on adjoining allotments. The local micro-climate on these sites is so different that on the south slope high solar inflow is required to achieve comfort, on the north slope solar shading is needed.

USING MICRO-CLIMATE FORCES FOR COMFORT

Micro-climate can be used to advantage. Warm external spaces are pleasant places to live in winter, cool outside spaces are comfortable in summer
But these changes to the home site's micro-climate also affect the interior comfort of the building. By creating variations in heatload, wind pressure and moisture on different faces of the home, the interior can be kept comfortably warm in winter and ventilated in summer.

This is described in detail in other information sheets below
Micro-climate occurs on every home site, with the combination of the land's existing features, and by placing the building appropriately on the site.
The first considerations in planning a home are:-
- which existing features on the land affect the micro-climate, and determine where the building is to be situated on the land for comfort,
- which way the building, its wall faces and openings are to be oriented to maximise comfort,
- and the heat, cooling and air flows which are created by the above for comfort(as covered in other information sheets).

THE BENEFITS

Buildings designed to use micro-climate are achieving substantially lower energy consumption to achieve the same comfort as conventional buildings; anything between a half and a sixth of normal energy use. That is a lot of money saved on annual operating costs.

ECOLOGICAL DEVELOPMENT
Micro-climate is consistent with ecological development principles because the existing features and ecology of the land gives a sound guide to the micro-climate potential and features which should be incorporated in buildings for comfort on each site.

Other information sheets set out some of the detail design options available to enhance the energy savings inherent in good micro-climate building design.

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  SUMMER COMFORT 

  WITH  CROSS   

  VENTILATION
Every day the sun tracks through the northern sky over Australia. Each building casts its shadow on its southern side, and reflects the sun's heat from its northern wall and adjacent ground
South Australia is situated in an arid fringe zone, with a substantial summer heat load where building cooling can be a major energy user
The naturally occuring heat imbalance around buildings described above can be used to improve comfort in buildings in South Australia in summer. Several complementary actions are involved.

As air temperature increases locally, that air parcel expands and reduces in density. Such a low density air parcel has a higher temperature than ambient, and is forced upward by the surrounding ambient air temperature and pressure. This takes the form of thermal convection. This is a common meteorological phenomenon.

On the northern side of a building, this temperature imbalance can be exentuated by constructing hard wall and ground surfaces which reflect solar heat, and these can be formed into a sunken or walled courtyard configuration to maximise the temperature imbalance created.

As air humidity increases, the density of that air parcel increases and the temperature decreases because the latent heat capacity of the air also increases.

Buildings cast shadows to their south. The air in this external area abutting the building is cooler than ambient. This air temperature can be further contained by adding more shade in the form of verandah or pergola, and adding humidity with vegetation, spray or drip irrigation or water features including fountains.

Buildings designed with both these micro-climate features are suited to summer cross ventilation. Opening of windows on north and south sides allows cool and humidified external air from the southern side to infiltrate the building while the building air volume is drawn out to the north by the thermal convection.

The calculated effect of this mechanism in an effective installation is up to 9 air changes per hour. The effect is to create air changes within the building with cooler than ambient air suitable for comfort in summer conditions. The pre-cooled low volume cross ventilation is created with little on-going or recurrent operating costs.

Micro-climate generated cross ventilation is based on simple and well understood meteorological phenomena.

Their application to individual buildings should however be undertaken with care. Poor building and landscape design in relation to the building's unique site and location can negate the effects being sought.
For a new building, the site should be assessed with a view to the naturally occurring hot and cool spaces. North facing slopes, depressions created by both landform and vegetation, soils, rock outcrops; all form favourable hot spaces
In existing developments, adjacent overshadowing by other development, and heat absorbing building facades reduces adjacent hot space potential.
Surfaces suitable for heat reflection should be selected and sited to reflect heat into the external space, not to the building. Light colour matt surfaces are more effective than dark colours. Both high thermal mass and heat reflectance materials are suitable.

Sunken paving with retaining walls or walled courtyard exentuate heating by avoiding wind chill cooling of the space, and minimising air inflow directions, a wall of vegetation can be also be suitable.

For cool spaces, shading by both built enclosure and vegetation are suitable
Pergolas, trellis, and vine. Verandah materials should resist heat transfer through the roof. Light colour and insulation or proprietory reflectance surfaces are suitable.
External ground level raised in relation to the building allows the cooled air to descend, exentuating throughflow. Walls and vegetation barriers are not beneficial
To maximise cross ventilation, large opening areas in the building faces to both spaces should be possible
Written operating directions for occupants assist in maximising the effectiveness of the installation.

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  SUMMER  

  COMFORT WITH  

  CLERESTOREY   

  VENTILATION
A clerestorey is high level openable glazing, resulting in the room having a high or sloping ceiling, and associated with it a high, sloping or curved roof on the building.

This high level glazing can be situated over the centre of a room or building to introduce natural daylight into the house in addition to daylight through windows on the perimeter walls.
The result is a greater amount of and more uniform distribution of natural daylight within the room or building, reducing the need for daytime artificial lighting and thereby reducing energy use.
The clerestorey lighting offers privacy, and daylight clear of vegetation as a result of its elevated situation.

In cold climates, clerestorey can face the sun with a northern aspect, reducing winter heating costs.

The majority of South Australia is situated in an arid fringe climate where summer cooling is the major energy use
In this climate clerestorey faces south, allowing full daylight inflow without direct sunlight or heat.

The clerestorey also can contribute to ventilation and cooling of the home in summer
Because clerestoreys can generate airflow, their use in bushfire prone areas must be considered carefully. In situations where they can encourage fire ingress to the home they should not be used; where fire ingress potential is less extreme their use is conditional on other fire resistant features including wired glazing, metal mesh screens, shutters and frames being incorporated.

Ventilation .through clerestorey is generated by the variations in air pressure from windflow around the home
It can also operate in concert with thermal venting as described in the pamphlet `Summer Comfort with Cross Ventilation'.

As air flows around the building, upwind surfaces dam air to higher than atmospheric pressure. Downwind and sheltered areas contain air at atmospheric or lesser pressure
South facing clerestorey is situated in a sheltered area relative to South Australia's prominent northern summer winds. The combination of sheltered area between high and low roof, the reducing air pressure over the sloping or curved roof results in air outflow from the building when clerestorey windows are opened.

Effective ventilation depends on replacement air being drawn from elsewhere around the building. In summer the north winds are hot, dry and dusty, and direct ventilation is undesirable.
The south downwind side of the home encompasses shaded air which can be cooler than ambient temperature as well as at dust free atmospheric pressure.
This is suitable replacement air by opening south windows in concert with the clerestorey.

During summer weather changes characterised by south-west `cool change' conditions, opening the clerestorey to act as an air-in ram bringing cool air into the home to rapidly cool the structure.
The effectiveness of this action depends on opening a north window laterally in the home to encourage air throughflow.

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