Design Strategies
The four buildings recently constructed at the Ranger’s Station are reviewed below:- These are the Head ranger’s house, the Ranger’s office, the Laboratory and the Visitor’s accommodation building.
The Head Ranger’s House is a small, elevated, steel frame building with single skin infil walls lined with corrugated metal cladding. Large sliding panels in the living space open onto a verandah and the magnificent views beyond. A barbeque area at the front of the house provides an informal meeting place separate from the main house. The bathroom and laundry are located in a separate structure attached to the main house by a short elevated walkway.
The Ranger’s Office is of similar construction to the house, although local mud-bricks are used for walls and the material imparts a distinctive regional character to this building. The building comprises an office that provides the ranger with discrete views of the site, a briefing room and a small strongroom. An outdoor meeting area is located under a curved roof at the front of the building and links the more formal internal spaces. Low curved walls and bench seating in this outdoor area provide a series of discrete spaces for more intimate social gatherings: an important consideration in Aboriginal communities.
The Laboratory was re-constructed from material salvaged from an abandoned uranium mine in nearby Kakadu National Park. The main steel frame and the joinery benches were dismantled, transported to site, and reworked to suit the new requirements. Insulated wall and ceiling panels were fitted between the re-cycled steel frame to provide a sealed environment for the largely air-conditioned building. This resulted in a very economic building and put to good use building materials that would otherwise have been left to deteriorate. Although the most utilitarian of buildings, it is also the center of research activity at the Ranger’s Station.
Site Planning
Three of the buildings are located on level ground along a high ridge that falls steeply away to the south and west. The fourth building, the Ranger’s house, is constructed on the edge of this ridge a short distance from the other buildings at the Ranger’s Station to provide privacy. The Ranger’s office is centrally located within the Ranger’s Station complex. The Laboratory and Visitor’s accommodation buildings are located on a level area between the edge of the ridge and the access road into the Ranger’s Station. An important design consideration was to minimize on-site environmental damage, particularly during the construction of the buildings. The Ranger’s house and part of the Office are partially elevated on steel posts with a timber floor. This approach resulted in minimal site clearance and retained much of the tropical undergrowth.
Orientation to reduce sun penetration, to take advantage of prevailing breezes and to benefit from the magnificent views towards the Tomkinson River to the south and west guided the placement and layout of the four buildings. The Ranger’s house and Office conform to the more orthodox design approach in the tropics with the long axis of the buildings orientated east-west. Due to site constraints and to take advantage of views the Laboratory and Visitor accommodation buildings are orientated north-south. This less than ideal orientation is partially addressed through the use of dense landscaping to provide shade to the external walls, verandahs and habitable rooms.
The four buildings are geographically dispersed along the site and this separation suggests a small village-like atmosphere. Separate buildings with smaller footprints, constructed over a three year period, resulted in minimal environmental damage. Disturbed areas were re-vegetated as part of the project and planting quickly regenerated in the tropical climate.
The form of all of the buildings is relatively simple with economy of size an important design strategy to reduce capital costs and the cost associated with transportation of materials. The outdoor verandah areas of the Ranger’s office, the House, and the Visitor accommodation allow for expansion should additional space be required. The project reveals how, through careful design, large and costly enclosed spaces are not required in remote settings and that space requirements are, perhaps, better served by providing smaller enclosed spaces with low-cost external verandahs to cater for the occasional larger meeting.
Energy Use
Response to climate
Natural ventilation was maximized to all buildings although functional imperatives (the desire for air-conditioning) dictated a less rigorous approach with the laboratory building. The extensive use of operable windows and louvres, timber slats, large sliding doors, screen walls and part-height internal walls all act to ensure cross-ventilation through the buildings. The wet areas to the Ranger’s house are designed as a separate structure with part-height external walls to maximize ventilation to what is often a very damp space. Ceiling fans are used throughout all habitable rooms to complement natural ventilation and provide a low-cost means of increasing internal air-movement within the buildings. Spaces of greatest potential occupancy are the most open to optimize the thermal performance of the building and to compensate for space heating through population density.
Effective sun control is imperative in the tropics to prevent undue heat load on the building and occupants. It must be remembered that the sun can be both north and south of the building depending on the time of year and appropriate strategies need to be implemented to address this. Reducing solar gain on the building envelope is particularly important where air-condition is to be used. A steep pitched roof with wide overhangs, appropriate orientation, wide verandahs and landscaping are all used to ensure the buildings at the Ranger’s Station are shaded. In some instances, however, optimum orientation could not be achieved and sun control appears problematic, particularly in the later afternoon.
Natural lighting is optimised through the use of glass louvres and windows, roof lights, narrow plan form buildings and consideration of orientation. However, glare and sun penetration through windows must be avoided and screening, vegetation and orientation address this issue.
A solar power electricity system meets most of the daily power needs of the Ranger’s Station with the exception of the air-conditioners. A series of photovoltaic cells are mounted on the roof of a nearby shed with the storage system (batteries) located in a recycled shipping container. A diesel generator provides back-up power to charge batteries, to run the bore pumps and to run the air-conditioning in the Laboratory building.
While there is no restriction on the availability of power due to the generator, energy consumption, and consequently fuel consumption, is reduced by a number of techniques:
Passive design principles reduce the need for mechanical cooling in buildings for most of the year.
Mechanical cooling is limited to ceiling fans with the exception of the air-conditioned laboratory.
Low energy fixtures, such as fluorescent lights, are used wherever possible.
External lighting is reduced to a minimum.
Natural gas is used for cooking and refrigeration.
A climatically controlled internal environment was an essential brief requirement for the laboratory building. The surrounding verandahs and use of insulated wall and ceiling panels considerably reduced heat loads on the building with a corresponding reduction in energy use. Although the room air-conditioners used in the project are not the most energy efficient system available their use was dictated by budgetary constraints.
The provision of ceiling fans and operable sliding windows to all rooms in the Laboratory allow air-conditioning use to be reduced in the cooler months. However, the design parameters for an air-conditioned and non-airconditioned space cannot easily be reconciled within a single constructional system resulting in the need for choice. It was recognized at design stage that preference would be given to air-conditioning and the building was designed to optimize air-conditioning performance and as a consequence reduce energy consumption.
A number of passive (non-mechanical) and active (mechanical) strategies were adopted to ensure the buildings were comfortable for the users. The principle approach, in line with the objective to reduce energy costs, was to rely on passive design principles. These included:
Orientation to reduce solar gain and catch prevailing breezes,
Large overhangs on roofs to provide shade to walls and openings,
Extensive louvre windows, screens and door openings to maximise cross-ventilation,
Rotary and gable vents to exhaust hot air.
Roof lights to provide natural lighting to rooms.
While active systems were used to modify the internal climate they were restricted to ceiling fans in all habitable rooms and the provision of air-conditioning in the laboratory areas as a work-place essential in the tropics.
Embodied energy
The measure of embodied energy in construction systems is often difficult to quantify as the point where measurement commences can be contested and the ramifications of energy use are not always immediately evident. Where to begin and what to include are often difficult judgments to make. However, with any building project in remote regions, the energy use resulting from transportation can be substantial. The direct and most obvious cost – in fuel consumption - can be easily quantified and, through design strategies, this energy use can be reduced. Design strategies adopted in this project included reducing the size of the buildings and hence the amount of material that needed to be transported, using lightweight steel framing and cladding, and advantage was taken of locally available mud-bricks.
Environmental
Water and waste management
The selection of services for this project was guided by the principles of autonomy, sustainability and low maintenance. A reliable and good quality water supply is available from a nearby spring and water is pumped to a stand tank on site. Hot water is provided through roof mounted solar hot water units. Toilets are predominantly drop toilets located away from the buildings. They are used to reduce water consumption and limit the need for ongoing maintenance. The Ranger’s House has a composting toilet with separate ground-water disposal in a transpiration bed.
Bio-diversity
The preservation of existing landscaping was an important design consideration that guided all work on the Ranger’s Station. The decision to design separate buildings resulted in minimal disturbance to the sites during construction. Considerable effort went into re-vegetating disturbed areas and introducing shade trees following construction. Three years after completion the vegetation has regenerated and landscaping contributes positively to shading the buildings and moderating internal conditions.
Material selection for the four buildings had to respond to a number of pragmatic imperatives:
High strength to resist tropical cyclones
Lightweight for ease of transportation.
Low maintenance
This dictated the use of a steel structural frame as timber framing, perhaps the optimum material, becomes, in cyclone regions, both complex and costly to detail with a high maintenance component. Timber was, however, used for flooring in some buildings and corrugated metal cladding was a lightweight option for roof and walls. Locally manufactured mud-bricks were used extensively to reduce reliance on ‘imported’ materials. The use of mud-bricks made from the red/brown earth of the region also imparts a specific identity to the buildings. This results in a closer fit between the buildings and their geographical context. Finishes in the buildings have been kept at a utilitarian level to reduce maintenance and to meet budgetary constraints.
Socio-cultural considerations
While change and radical intervention is part of traditional land management techniques adopted by Aborigines for centuries, these approaches are undertaken with a long-term goal in mind. As a consequence, Aboriginal clients tend to have a commitment to the region and are often more receptive to the adoption of a sustainable approach to design. Extensive consultation was undertaken with the Bawinanga Aboriginal Corporation Executive. Models, sketches and drawings were used to communicate energy saving principles at design stage to elicit a commitment from the client and end users. In extreme climates expectation often gravitates towards mechanical means of climate control with associated high energy costs. In this case passive design principles were adopted for all but the purely utilitarian laboratory workspace resulting in considerable energy savings.