From passive solar design to Passive House

At the outset, we expected that designing an efficient house for a large flat block with a north and east aspect should be straightforward. The block is also free of other complications that the river reno had such as flood height, bush fire risk and winter shading. While we had briefly entertained the of a project home, it quickly became clear that it wouldn’t be easy to find one with the right layout to take advantage of the block’s orientation.

We built our current house using passive solar design principals and love the comfortable summer temperature and warm winter light. Scott had continued to diligently read Sanctuary and Renew magazines for years and more recently discovered the Under Cover Architect podcasts, so we are firmly in the sustainability camp.

As Scott spent time researching his many questions about things like how much insulation is enough, how airtight the building can be without causing air quality issues, how to improve on our current windows (which are double glazed uPVC but still see condensation on the inside pane) etc, he noticed that the German Passivehaus principles seemed to keep coming up as a logical end point of his inquiry. The more he learned about Passive House design the harder it has become for him to imagine an alternative that would fit as well with our values and ideals. Of course, I didn’t know how different ‘Passive House’ was to our previous approach. I was soon to enter the world of mechanical ventilation, vapour barriers and fear of thermal bridges.

Briefly, the five ‘pillars’ of Passive House are:

1. A well-insulated building envelope

2. Minimal thermal bridges

3. High performance windows

4. An airtight vapour barrier on the inside of the frame

5. Heat recovery ventilation

The really snazzy bit of the Passive House process is that those five principles are all modelled during the planning phase so you know exactly how much energy the house will require before you build.

The modelling gives the assurance that we will be able to achieve a comfortable living environment with minimal heating and cooling and no risk of mould growing in wall cavities. For anyone who is interested, the Australian Passive House Association has more detailed information.

I was particularly attracted to the promise of a warmer house in winter and, as a bonus, the ventilation system will filter out the pollen in spring that cause hay fever for two of our children. It surely must also help remove smoke when we have fire seasons like the one we just had too!

Gathering the experts

But where to start given the concept is still getting established in Australia? Fortunately, we knew a couple of people that could provide the detailed design input needed. We had met David Halford from 5C Sustainable Building Design at a ‘Speed Date the Sustainability Expert’ day organised by the ATA (now Renew) and the City of Greater Shepparton. While David was too busy to take on new clients at that time, his comment that ‘once you’ve seen how Passive House works, it is hard to go back’ stuck in Scott’s mind. Scott had also previously been talking to Luc Plowman of Detail Green about getting an energy assessment for the river renovation, so when Luc told us he had since added a registered drafts person to his team, the opportunity to have them work on our project really came together. Luc was actually the second Passive House building designer and certifier to be accredited in Australia, so we felt we were in good hands. Check out the Undercover Architect podcast where he is interviewed.