The Australian Passive House Association (APHA) has developed a simple App to demonstrate improvements that could be achieved to the government's designs for 7-star energy efficiency homes.

The VCA was disappointed when the 7 star house plans were released as virtually all the house designs suggested single glazed aluminium windows were adequate in the building fabric (see our article), even in cooler climate zones like Victoria and Tasmania.

The App - freely available on the APHA's website - indicates that by simply improving the windows of a 7 star NatHERS design in Melbourne, 22% less energy would be consumed and thermal comfort would be improved markedly. Using 'best practice' windows would reduce energy consumption by 47% compared to the NatHERS 7 star design, and using 'excellent' windows would cut energy usage by 56%.

Although 'best practice' and 'excellent' are not openly defined by APHA, this tool backs up our argument that windows should not be forgotten in designing better insulated homes to improve energy efficiency in the built environment. As well as windows, the App allows users to explore improvements to walls, roof, floor, air tightness and  thermal bridges. However, improvements to walls, roof and floor (presumably already well insulated under the 7 star NatHERS design) don't yield anything like the same results as improvements to the windows.

Air tightness is another approach to achieve significant improvement - uPVC windows systems can help in this achievement too.