8.3 The Gap, Queensland

BLAKELY RESIDENCE

Conventional techniques and materials were used in the construction of this Brisbane house. It constitutes a low cost solution to the requirement for an environmentally friendly house that uses minimal heating and cooling equipment and is both pleasant to inhabit and normal in appearance.

THE BRIEF

The requirement was for a family home with four bedrooms and an open kitchen/living/ dining space with a large deck.

The family have an interest in, and knowledge of, passive thermal design principles. They wanted a thermally modelled house that made good use of natural daylight. They also wished to take advantage of the available views across a valley to hills that lay to the north-east and east of the site.

There was one key conflict in the design requirement. The clients wanted an open (floor to ceiling glass) light, timber feel to the house. However, they also wanted a heavy weight approach to controlling thermal comfort.

The plan of the house reflects the living habits of the family. It is essentially a long pavilion containing a row of rooms off one side of a hallway axis. The bathroom and kitchen are lean-to pavilions off the other side of the hall. Being environmentally aware people, the owners wanted to explore a range of environmental design issues (such as choice of construction materials and stormwater/ water use) which would not result in an unconventional home.

In the end, the design of the house was an exercise in implementing sustainable practices and technologies within the cost and familiarity constraints of a fairly normal home in the suburbs, site and climate.

SITE AND CLIMATE

The site is located at The Gap, a north-western suburb of Brisbane. The area is characterised by a valley running west to east with a microclimate slightly different to the typical Brisbane climate. Brisbane is hot and usually humid in summer and cool, sometimes cold and dry, in winter. For at least 5 months of the year the climate is very pleasant. The site is above a secondary valley that runs southeast allowing access to cooling breezes. Hills to the north and east restrict the usual cooling afternoon breezes from the north-east.

The site falls fairly steeply (4m in 30m) from west to east. It is located behind and above a house dug into its site at the street. Access is via a long narrow drive. This means that stormwater (run-off and seepage) was an important issue. The site had been completely cleared of trees and the density of the estate meant little overshadowing. [See: 4.2 Design for Climate; 2.2 Choosing a Site]

DESIGN CONTROLS

DESIGN CONTROLS While the site has no special development controls, it was covered, like the surrounding estates, by a brick veneer covenant. This is greatly at odds with the basic concepts of more sustainable design. Interestingly, this is seen as a way of controlling quality. The issue was dealt with by partly cladding the house in lightly rendered block veneer although some minor legal sparring did occur.

BROAD DESIGN RESPONSES

In the design, special materials, construction details and technologies were kept to a minimum.

Energy efficiency measures included orientation of the house (long side to the north), controlling solar access, the use of thermal mass and good insulation.

Issues of stormwater control and water use efficiency were resolved comparatively simply using an agricultural system.

While the house is designed in detail for the specific site, context and people, the principles behind it (practices and technologies) are applicable for any house design.

SPECIFIC DESIGN SOLUTIONS

Orientation

The site and its context allowed a simple orientation solution: a rectangle with long sides to the north and south.

Orientation to the north is preferred because for a good part of the day, especially during summer, the sun is at a reasonably constant height above the horizon. This means that solar access can be easily controlled with simple fixed shading devices such as eaves and window hoods.

The western end of the house is tucked into the side of the slope to the west, providing good protection from the low hot western sun.

The east end of the house rises out of the ground, giving a lot of access to east and northeast sun. This will need more control in summer although bedrooms are protected by the verandah and living areas.

This orientation not only suits the sun but also suits the direction of prevailing breezes/ winds in Brisbane. [See: 4.3 Orientation

EVALUATION

The house was given a 7.7 star rating for a passive thermal (heating and cooling) performance using the AccuRate software.

The house has been temperature tested by the previous occupants. Three thermometers were placed on the verandah, in the tropical room and in the thermal mass area. During a cold snap in winter, the interior of the house stayed above 17°C when it was about 1°C outside on the verandah. In a recent heat wave, while the outside of the house was above 40°C, the interior of the house stayed below 30°C. No controlled management of the house was carried out.

In the end it is important to note that it is not the house that uses energy, but the people who live in it. The house provides an opportunity to easily reduce energy bills without suffering to do so.

After a period of occupation, the house appears to be a fairly successful attempt to implement some key sustainable development practices and technologies in a cost effective way.

Regardless of the theory behind the design and construction, the house is very pleasant to live in. Everyone who visits it (not just designers or clients) expresses this.

Principal author:
Jim Gall

A joint initiative of the Australian Government and the design and construction industries.

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