Rapid Creek - Darwin

This new passive solar house has five occupants who enjoy year round comfort in an
environment of wonderful natural surrounding features and established tropical gardens.
The architect was David Bennett of Bennett Design and his brief was to create a
3-bedroom residence with a separate home office for work and study.

Design for the residence was to be uncompromising in its approach to tropical design, providing
the occupants with the maximum comfort from the climate whilst still being simple, durable,
Secure and practical. Comfort levels within the residence depend upon the principal of
maximum ventilation. The green surrounds keep the occupants cool in a hot climate
with extreme humidity. Numerous voids in the two storey building allow any hot air build
up to rise through the building to a ventilated ridge and into a double-buffered roof cavity. Coloured
concrete slab on ground and masonry components to the lower levels are well shaded and provide a
cooling affect to the lower part of the residence. Upper levels are made of lightweight materials.

These materials are reflective and also dissipate heat rapidly after sunset allowing for cool sleeping
areas. Cross ventilation is essential to the design's function. The lower openings are provided only
with ss mesh for insect and security screens. These large unimpeded openings provide unlimited
air movement that can be captured from any direction. Large roof overhangs and awnings limit
the intrusion of sun and rain into the house. Reflected light from the numerous openings and the
use of reflective lining materials has reduced the need for artificial lighting to the interior. No
air-conditioning in the house is required, but ceiling fans provide air movement on hot
days when there is no cooling breeze.

Upper levels of the house, where the openings are exposed, have been treated with timber
louvres for privacy. These also limit the intrusion of the tropical sun while still allowing maximum
ventilation through the house and reflected lighting. The upper roof cavity is fully ventilated at
the top and eaves. Insulation has been applied to the underside of the roof cladding and
above the ceiling lining to limit heat build up in this cavity.

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Energy efficient concepts such as orientation, natural ventilation and daylighting were adopted throughout.Hot/humid climates, such as is experienced in the Northern Territory, endure high rainfall
during the three to four month wet season along with long periods of relatively dry and sunny weather
for the remainder of the year. Daytime temperatures usually exceed comfort levels.

For these climate areas there are specific passive solar design principles best suited to attain
maximum comfort levels all year round. Natural cooling is achieved by making best use of available
breezes. Cooling design principles include elevating the house to increase exposure to cooling
breezes filtered through existing tree cover, the provision of a large overhanging roof in all
directions to minimise direct solar heat gain, the ventilation of all the eaves edges of the roof to
at least one metre high and the use of a central ventilated ridge that functions like an aeroplane
wing to create uplift and draw cross-draughts of breeze through the house during low breeze
conditions and allow convective or stack ventilation.

Living areas and bedrooms can have multiple sliding glass doors with matching flyscreen doors.
A cyclone proof shutter can be fitted in the bulkhead over the doors. This allows equalisation
of wind pressure inside and outside the house. The house requires cross ventilation in order to
attain thermal comfort. The walls are insulated and two layers of insulation in the roof system
reflect radiant heat and prevent heat loads from reaching the structure. Convection and
cross ventilation remove heat from the building. In hot humid climates with high humidity and
low diurnal temperature ranges, thermal mass is of little benefit. Low mass construction responds
rapidly to the effects of cooling breezes and has lower embodied energy - particularly on a remote site

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