The Rubix Collective team of building designers in Newcastle estimates that the cost of upgrading to a passivhaus costs about $450 more per square metre than a standard home at time of writing, but payback of this initial outlay can be immediate. With heating and cooling reduced to practically zero, the costs saved are often greater than interest-only repayments on a construction loan for the upgrades. Excess savings above and beyond the interest-only repayments could be used to pay off the principal slowly over the long-term. (Financial advice is general in nature only).