If you are building a passive house, you may want to consider going through PHPP (Passive House Planning Package) and Certification.  

PHPP is recommended as it provides a scientific analysis of how your house will perform at the design stage.  This allows any tweaking to the design to be made to meet certain criteria before the build starts and changes can no longer be made.  It is based upon physical algorithms and we contract our specialist PHPP advisers to undertake this work from around $2000 + GST.  You do not need to apply for certification if you only want PHPP completed.  We have a few PHPP advisers we can use but it is important to decide upon this at the start of the design process as information can begin to be collated for the subsequent calculations.

At the end of the exercise you will receive a report stating what your heating and cooling loads will be.  It will tell you whether your house will overheat or be too cold and what areas of the design could produce a better outcome.  It enables an informed decision to be made and consideration of any additional costs compared to the benefits it may provide.  For example, your PHPP calculations may reveal that you need to spend an additional $40k and go to timber windows in order to achieve full passive house certification rather than being just below it.  Your informed decision may be either that you can still achieve a high performing passive house and accept you would not get the certification or decide that gaining certification was your priority and the additional spend is justified.