Energy efficient design

Design standards of energy efficient housing aims to minimise energy consumption of non-renewable resources for heating and cooling and hot water. The associated advantage of this is to reduce costs borne by the householder. Cost effective energy efficient housing is usually easiest to achieve at the initial design stage by integration of the dwelling and the site. This allows maximum use of natural elements such as solar access and air movement, and enables the development of interior design elements to produce a high degree of comfort while minimising and conserving energy use.

Although ACTHERS (ACT) is based on the potential of the design to reduce energy use, the behaviour of occupants and the energy efficiency of major appliances are also very important in overall energy consumption.

The Scheme is based on extensive computer simulations of housing performance in various Australian climates. It focuses on insulation, orientation (of living areas and windows), air leakage and other design features to provide a comprehensive picture of the house's potential for reduced energy consumption. Design measures which achieve better energy efficiency include:

Windows are a critical element in energy efficient house design, as unprotected single glazing allows the rapid transfer of heat into a residence in summer, and out in winter. The larger the window, the greater the transfer of heat. As living areas are those most commonly used, thermal comfort in these areas is important.

Where it is not possible to secure northern window access for every room, priority should be given to locating as many as possible of the living areas on the northern side of the house. These areas need to be comfortable. They should optimise natural light during winter and be shaded in summer, improving overall energy efficiency.

In order to conserve captured heat within living areas, the house design should provide for doors which separate the living areas from bedrooms and service areas. Grouping rooms with similar uses will also assist in making the most efficient use of heating and cooling systems. South facing windows are useful for assisting cross flow ventilation, particularly in summer. However, their use should be carefully considered, especially with respect to their internal coverings. Without adequate insulation treatment, the south facing windows may also contribute to heat loss.

East and west windows if too large, may gain large amounts of unwanted heat during summer and lose heat during winter. Selection of glazing and window treatments for summer shading and winter protection is critical to the overall performance of the residence. With its ability to reduce the amount of energy needed to heat or cool a house, insulation is an important element of energy efficient design that can be added to a home.

The BCA code has set the parameters for energy efficient design as follows:

Insulation assists in retaining any energy input to a residence, whether for cooling or heating, and whether achieved by solar access or an appliance. This reduces the rate of turnover in the replacement of that energy. The use of building materials with high thermal mass (the ability to store heat) is also of value to an energy efficient home. Concrete floors and internal masonry walls are examples of materials which assist in the regulation of internal temperatures.

High thermal mass is particularly important in climates where summer an winter temperatures vary greatly, and large differences occur between minimum and maximum daily temperatures.

Unwanted or uncontrolled ventilation or air leakage may add significantly to the costs of cooling, and especially heating a home. The use of weather strips and door seals will improve the overall performance of an energy efficient house, while reducing energy consumption and costs.

However, ventilation is also an important component for regulating internal temperatures during summer and for allowing fresh air into the house to control dampness and mildew if required.

Cross flow ventilation during summer is enhanced by appropriately placed windows and doors on all sides of a house. Other elements may further add to the energy efficiency of a home. However, these do not form part of the energy rating assessment. These include:

On average, an energy efficient home is up to 5 degrees warmer in winter and up to 10 degrees cooler in summer. As well as being more comfortable all year round, an energy efficient house also has much more natural light in areas most commonly occupied, including direct sunlight which does not detract from internal thermal comfort.

The principles of energy efficient design do not limit housing choice, but rather create opportunities to use a variety of design features to produce an attractive and functional home.


There are 6 special conditions under which an exemption may be claimed from achievement of the minimum house energy rating requirements for new houses. Where one or more of the special conditions apply, approval is subject to provision of ceiling and wall insulation, and under floor insulation to timber floors: