Once you have orientated your floorplan to the northern sun, you need to site your windows to bring light deep into each room.  To get a good rating most of the glazing in Melbourne should face north.  This is followed by east (to get the home warming early in winter) and then west with appropriate summer shading, and lastly south.  In Melbourne the sun rarely shines in from the southern side, except early morning and late afternoon in summer, when you don't want it!  Southern facade though, is important in Melbourne suburbs, for picking up the prevailing summer southerly sea breezes, so we often include judiciously placed windows to facilitate breeze paths through the house. 
(Note: You should also take care to include views and aesthetics in your considerations when placing windows.)

While glass is great during a winters day for letting in sunlight, it is terrible at night, as it is a great conductor and windows represent large thermal 'holes' in the skin of the house.  It is therefore always a good idea to use high performance, double glazed, low E coated, argon filled windows.  These are around 3 times more insulative than single glazing, and keep the heat gained during a winters day in much longer once the sun goes down.  Conversely, with appropriate eaves, they keep the heat out 3 times better in summer. 

Frame material is also an important consideration.  Aluminium and steel are very durable, but are even better conductors than glass, so thermally are a poor choice.  Composite windows, where aluminium is on the outside and timber on the inside, or thermally broken alumiunium frames, are both better choices.  PVC windows can also perform well, but PVC can be polluting, and though recyclable, are not readily recycled in Australia.  Timber windows are also an insulative frame material, and can be beautiful, but will need more maintenance over the life of the building.  It is also important to consider where the timber has come from, as poor choices can lead directly to habitat loss.  And then there is cost, mechanism type, size & opening limitations, to also consider...

So, what is the perfect window?  There isn't one.  It will depend on aesthetic, budget, and performance requirements particular to the job.  Knowing the issues however can help make a balanced decision when the time comes.

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