Architects, how are your designs going to go with glass to floor ratios of 20% (you would be currently 40-60% and randomly higher) —I am not qualified to give financial advice but ……. time to buy shares in companies that have thermally broken windows.
The RIS for energy efficiency reckons the costs will be approx. $2,000 – $3,000 to go from 6 to 7 stars. (Some dream world where cost benefit analysis & the BCA meet)
I used 3 of my recent ratings (2 project builders & 1 custom builder) and changed them to 7 stars and worked out the cost difference range to be $16,000 (small house/perfect orientation) to $87,000 (large two storey/not the best orientation due to the lot purchased by the owner) or 2.5% to 12.6%.
The RIS used glass to floor ratios of 15% to 20%, and is really only reporting insulation and ventilation (ceiling fans & roof ventilator) costs as the cost to upgrade and did not include real world markups & gst in the costs.
My ratings are real houses, real builders costs etc.
Whilst I agree with improving buildings performance, don’t know that 7 stars is the best idea, PV and blower doors. These would be far lower cost and far more measurable and realistic.
What do they say “If you aren’t keeping score, you are just practicing” natHERS certificate is a bit of paper that says if correctly built, it would achieve x stars, but we have no method of testing or checking this.