It is usually easier and cheaper to incorporate these principles at the design and building stage of a home.  Certain features are however possible to retrofit and still reap the economic benefits.

Choosing the right orientation for home placement is sometimes restricted by the aspect of land chosen.  It is important however as good orientation can reduce the heat load of a house and the need to artificially cool it to stay comfortable.  Ultimately the aim in a tropical climate is to restrict direct sun from entering the house all year round while increasing access to prevailing breezes.

In terms of positioning a house on a block the general rule is to position the house facing north, with the long axis running on an east - west axis. 

In the north of Australia, the sun passes overhead in the southern part of the sky in the summer months and overhead in the northern part of the sky in the winter months.  Therefore it is important to shade the long sides of the house facing north and south.

Prevailing breezes in this area tend to come from the south - east, so it is important to orientate openings to receive these.  In terms of orientation, another point to consider is obstructions in this direction in order to maximise airflow around, over or through them.

Source: Your Home Technical Manual

In a tropical climate, the aim with glazing is reduce the amount of heat entering a house.  When purchasing windows, look for the WERS rating, to get an idea of the ability of the window to keep heat out.

The use of shading is crucial to keep a house cool as heat entering through windows is the largest source of unwanted heat gain in a home.  Windows to the north and south require shading in the tropics.  Glazing to the east and west is different as the angle of the sun rising and setting cannot be entirely excluded.  It makes good design sense to allow for flexible shading in these directions so you can control when to shade.  In the summer months restricting the hot afternoon sun is a blessing but in winter it can be cool enough to bask in the sunny glow.

Ways to shade are numerous:  eaves, pergolas, awnings, blinds, sails, plants are all good examples of shading.  Be creative.

Thermal mass refers to the ability of a material to absorb heat. 

Materials of high thermal mass such as bricks and concrete absorb heat energy during the day and as the temperature drops at night, the heat is released.  This is advantageous in the cooler climates as high thermal mass acts as a thermal battery. 

Most of the year in the tropics, it is warm enough without a thermal battery.  Cairns has a low average diurnal heat range (difference between day and night temperatures) of 8.2 degrees.  This means that a high thermal mass is not highly recommended unless it is with careful consideration of house design.  This is because materials of low thermal mass react well to cooling breezes and cooling is what we are after.

However, it is possible to couple well insulated and shaded thermal mass, in innovative ways to achieve a lower evening temperature.  It is also worth considering the colour of paving/tiling around a house, as pale colours will not absorb as much heat as dark colours.

Insulation is paramount to the comfort level inside a house as it acts as a barrier preventing heat from entering.  It does need to be installed with consideration so that it doesn't prevent heat from leaving the house. 

As with the other design principles, it is important that an interactive approach between them is adopted.  Check for the R-value of insulation before purchasing to ascertain degree of effectiveness.  Building Codes now dictate certain mandatory levels of insulation for increased energy efficiency of buildings.

There are two main types of insulation:

1. Bulk insulation - This resists the flow of conducted or convected heat.  It traps air in the material.  Common bulk insulation includes glass fibre, wool, polyester and polystyrene.

2. Reflective insulation - This reflects and resists radiant heat.  Radiant heat travels through air so reflective insulation is usually coupled with an adjacent air space.  Some examples of reflective insulation are reflective foil laminate which is made from aluminium foil laminated to building paper, reflective foil on bubble wrap, and reflective coatings on building materials.

The ceiling is the most important area to insulate as it is the major heat gain zone.  A combination of bulk and reflective insulation is ideal.  Walls are also important to insulate.

Natural ventilation is an excellent means to naturally cool a home.  It involves deliberately controlling the movement of air between the inside and outside of the house.  In a humid tropical climate, air movement over the body provides a sensation of coolness as perspiration is evaporated.

Cross ventilation is often referred to and which refers to air entering through an opening (window or door) and exiting through an opening on the opposite side.  Openings placed on opposite sides of the building create a funnel effect which aids air movement.  To assist with this process it is worthwhile considering a house design which is elongated and of one room width.

Ventilation can be maximised using design techniques such as:

• Use louvers, casement and awning windows to channel air into the house.
• Deflect breezes into the house using vegetation or a fence.
• Design corner rooms with windows on adjacent walls.
• Include ceiling fans in the design