Passivhaus A Client’s Perspective

Passivhaus: A Client’s Perspective

We often find ourselves saying that we have the best of the best when it comes to clients. One of our clients has taken the time to detail some of what he has learned and observed throughout the process of constructing his dream build.

As you know, every step along the way is as important as the next: especially in Passivhaus construction.
Here is what John has to say:

Here are some thoughts on Passive Houses (based on a sample size of one!) following Friday’s blower door test.

The design and building of Passive Houses (PH for short, also used is the German term PassivHaus) in Australia is unfortunately still rare. Australia is well behind Germany for example. My neighbour in Manly did her architecture degree in Germany in the 1990s and PH principles were a standard undergraduate subject there even then. A few architects, designers and builders are versed in PH techniques here, but a lot of people (especially potential clients) have never even heard of them, such is the grossly unsatisfactory nature of Australia’s poorly designed housing stock and consumer ignorance. PHs are particularly well suited to extremes of temperature, including the hot weather experienced in much of Australia, the prevalence of which is increasing of course. 

The main principle in PH design is thermal efficiency. This is maximised through such simple things as:

  • Building orientation,
  • Size and location of windows,
  • Using the right materials,
  • Insulation,
  • Elimination of thermal bridges, and
  • Prevention of building leaks.

Most of these things are easily planned early on but are relatively cheap in themselves. As they say, if you fail to plan you are planning to fail. Like painting, preparation is critical.

At the same time as applying PH principles to the design and construction of a building, the use of a Heat Recovery Ventilation System (HRVS) and safe materials allow the building to be healthier for its occupants, reducing or eliminating asthma and other respiratory conditions, and almost eliminating the growing hazard of bushfire particles.

It is estimated that other things being equal the cost of constructing a PH is roughly 15% more than an equivalent conventional (sub-standard, i.e., complying with the currently applicable formal building standards) house. Some people say it’s more and some say it’s less, but it seems like great value to me, a no-brainer when you take long term energy, transport, and medical costs into consideration. Whether a house is a “custom build” or an “off the shelf” design is a separate matter. So is the relevant bushfire resistance rating for the house’s location (although an HRVS can reduce the breathing in of smoke, ash, and dust dramatically). The former costs more than the latter obviously, but PH techniques can be applied to both. And even if a house is not formally certified a PH, there are a lot of useful PH building techniques which can be borrowed to make it better and cheaper to run.

There is a lot of discussion of Australia’s shortage of housing at the moment, and governments have announced some funding to remedy this, but I’ve not heard a word about this new housing being energy efficient beyond the newly announced energy star system. If true, this is disgraceful- residents and taxpayers are both being ripped off, and presentations at hospitals for respiratory diseases can only increase. I hope I’m wrong….

It’s also common for politicians to talk about the cost of living. A PH has minimal energy consumption and is therefore cheaper to run. Mine will be off grid in a location (the upper Blue Mountains) which can be notoriously misty and cold for days on end at any time of year, but all my energy (including that for the car) will come directly from the sun. It will cost more to buy the technology, but I won’t pay a cent for energy in the following decades.

[Fun fact: in NSW in 2018-19 (the last financial year before COVID) our energy consumption was split thus: transport 47%; industrial 33%, residential 11%; commercial 9%.]

The photos attached are of my PH build at Blackheath which is just past halfway through. The windows have been fully installed, but the gyprock inside has not yet gone on the walls or ceilings, so it is the ideal time to track down and seal any holes, even the pinhole-sized ones, in the building envelope. My house will be complicated in shape, have large windows and be on the large side for one person, so the sealing is more difficult than for a small house with a simple shape. Nonetheless the initial test was (I understand) 0.54 air changes per hour (AC/H), and with further sealing next week it should come down to around 0.39 AC/H. That figure will rise slightly once the gyprocking of ceilings and walls reduces the effective internal volume. The threshold which a house needs to meet in order to be certified a PH is a maximum of 0.6 AC/H. Conventional houses often have 12.0 AC/H, and more on a windy day- glorified tents! Yesterday (a clear spring day with a gentle breeze) with everything closed up, the house was warm inside in the early morning and cooler than outside later on.

Some notes on the photos:

  • Blower door from the outside- note the small squares of flashing tape used to cover electricity cables.
  • Beth doing blower door test- it’s a data-driven house. Mark Davis, our PH consultant, sent us a 9Mb spreadsheet with the thermal efficiency calculations for the design.
  • Laundry and utilities room- some of the HRVS ducting. Most of the rooms have both an inflow and an outflow duct. Note also the lagged hot water pipes on the wall and ceiling, and the use of black flashing tape on all penetrations, joins and window and door frames.
  • The carefully constructed PH join- the junctions of the factory-made cassettes and other external surfaces are places where leaks can occur. Penetrations for piping and wiring can also be problematic. Here, flashing tape and Passive Purple ($200 a container) have been used.
  • Corridor- the house has been sealed and all the wiring and plumbing roughed in. The ceiling grid has been fixed, so once the initial blower door test has been done the gyprocking can take place.
  • External pictures- the cladding, painting, and landscaping are yet to be done. The bright white of various surfaces will change dramatically.

I can say that without doubt this has been one of the most educational, satisfying (and stress-free) experiences I’ve had in my 7 decades.


Share this post