The building comprises a 345m2 structure which houses one large 105m2 space, with supporting facilities including staff offices and kitchen. Attached to the main space is a 50m2 outdoor ‘classroom’.
The brief for the project, the first permanent building at the Botanic Garden, was to set the benchmark for future buildings on the estate and to provide a unique multi-function facility that demonstrates high standards of ecological sustainability, within a very modest budget.
This was achieved through, amongst other things, siting the new building in the location of an existing structure, recycling the steel structure and aluminium windows from the earlier building, the use of low maintenance materials, the thermal management of the building via a ground coupled, water based air conditioning system and the inclusion of a series of plywood clad, vertical wall openings that act as alternatives to conventionally glazed windows.
The building, although relatively small, achieves a strong presence through its elongated form, the use of tripartite massing, soaring roofs and a 30m long verandah facing onto the adjoining open green.
In keeping with its setting and environmental agenda, the building uses a steel frame which is then clad in a combination of vertical and horizontal radially sawn Silvertop Ash plantation timber, constructed of overlapping solid timber slats that will be allowed to age to a soft grey, enhancing the bush setting as well as removing the need for the use of environmentally damaging finishes.
Internally, as with the outside, the building is lined in timber, being blackbutt veneer panels, a robust, low maintenance wall finish which gives the interior a rich spatial quality, strongly contrasting with the exterior environment and creates a unique, warm and inspiring space.
The rich, dark timber is highlighted by the continuous band of south facing clerestory windows and by the 13 plywood clad ‘windoors’ on the northern side of the building.
These ‘windoors’, which are casement type window openings utilising solid shutters rather than glass, achieve a higher insulation value, and provide less exposure to radiant heat gains, than a traditional window. When the windoors are shut the exterior of the building appears closed and solid, however when they are open the building has a strongly perforated appearance, which is further accentuated by the vertical timber cladding.
The thermal performance of the building presented a unique challenge due to both the high variation in seasonal temperatures at Mt Annan and the fact that the operation of the teaching space was not suited to a conventional passive solar design. The solution was to adopt a unique thermal management system that collects solar energy in the form of heat from the roof, stores that energy in a 40,000 litre below ground water tank, and then transfers that energy into the building by way of a heat pump to the polished concrete floors.
In summer the system works in reverse to cool the building by chilling the concrete slab.
The system, which has not been used before on a building of this scale, offers a viable and cost effective alternative to airconditioning for many building types.
The result is a building that can respond rapidly to a range of uses and conditions and is an essay in the creation of an environmentally intelligent building which transcends style to create a rich and inspiring educational environment.