With the release of the new BCA 2010, alongs comes the requirement for residential buildings and industrial buildings to increase their energy effiency from a 5 star to the new 6 star as of May 2011.
The Building Commission, BCA or Sustainablity Victoria has yet to release any information of what impact these new requirements will actually have on building budgets (predicted increase in your budget 5%) and along with the new BAL assessments and dependant upon your buildings rating, these two new requlations now increase your construction costs by an estimated 10%. So for the average small house renovation or extension being $180K, your construction costs increase will be $18.000, and that is not including the 25% average mark up from the builder.
So what are the main changes?
The main change is the glazing of the building, as with older homes, glazing was kept to a minimum, to reduce the amount of heat gain and loss in a building, as air conditioning was not around then, so rooms where kept small, thus allowing quicker and easier ability to heat in winter, and with the limited glazing and verandas, the rooms could be closed off to keep cooler in summer.
2010 designs are contemporary, modern with zoning, large open areas for families to enjoy open communication and living, lots of glazing and openings to allow the external nature and the building to become one, thus making the families life open, harmonised and relaxed. The down side of this is that the external glazing and openings takes up a much larger percentage of the external building, thus making heat gain and loss harder to control.
So the glazing is the main change, which being a higher percentage of your external building means that this is where the biggest increase in your construction costs come from, and most builders or architects will tell you, the cost currently for glazing, bi-folds etc is a big percentage of your construction budget.
Of course the building fabric which reflects heat gain in summer and prevents heat loss in winter will also slightly be increased to help maintain the buildings ambient temp of 21 degrees, but this will have only a slight increase in your construction budget as most of these are installed currently under the 5 star rating system.
So, to finilize, When your looking at your design, look at the amount of windows, doors in the external envelope, look at the direction the windows are facing and what percentages are facing north etc, how your building is orientated, and where the spaces are placed within the building to help reduce the effects of heat gain and loss, what external elements have been though about to reduce these impacts and finally how much thought has gone into the ceiling and control of the air movement within the building.