I was quite blown away by these stats — based on US figures — but no doubt quite similar here in Australia.  About half the energy used in the US goes into constructing, heating, lighting and maintaining the nation's buildings.

That's taken from an article by the Rocky Mountain Institute's Greg Franta based on IEA data.  Franta writes:

Just how important are buildings in the big scheme of things?

The built environment, with its broad diversity of sites and buildings, offers a huge opportunity to sustain a desirable quality of life on this planet. Buildings use most of our energy and deplete vast quantities of natural resources. They rely on non-sustainable material harvesting, extracting, and mining. And once built, they pollute water, earth, and air, and can harbor wholly unhealthy indoor environments.

On the contrary, "green" developments typically demonstrate sustainable practices of elegant design, offer responsible stewardship of the natural environment, and make wise investments.

Traditional sources of energy production and use are major culprits of atmospheric pollution. Buildings gobble close to 40 percent of the energy used annually in the United States to heat, cool, ventilate, light, and support other operations.1 This operational energy, plus the energy used to extract, harvest, and manufacture products, transport materials, and construct buildings means the building industry chews through more than half of all the energy used in the United States each year.
 
Integrated design leads to healthful and productive interiors, reduced operating costs, fewer environmental impacts, and restorative landscapes.

David Holmgren has mentioned that his family's passive solar house in Hepburn Springs, a showcase of sustainable architecture, would not be allowed to be built today because it does not meet the established environmental building code, which doesn't take into proper consideration thermal mass, or the embodied energy in the materials.  

Still a lot can be done with elegant solutions which work with the elements and seasons rather than against them.

Greenhouse.gov.au has some good building and design tips.

Ceres have a retrofitted an old weatherboard house which you can check out on Saturdays in East Brunswick.

It has a small greenhouse attached on the north (sun facing) side which can be used to both heat and draw cool air through the house, depending on which vents are opened.  The black rectangle on the right picture which looks like a door is a actually solar heat collector too.  Deciduous trees close to the house provide shade in summer and let light through in the winter.   The house also has working examples of a:

• Grid interactive PV power system
• Passive solar extension and additions
• Displays of insulation
• Energy efficient appliances
• Low embodied energy construction
• Natural floor coverings and finishes
• Urban rainwater harvesting
• Wattworks greywater system
• Solar hotwater & hydronic heating system
• Permaculture garden with low water tolerant plants
• And much more 

An extra step for builders would be to consider natural local materials such as stawbale or cob.  And if you think mud can't be stylish, check out the mud mosques of Mali…