Often, mechanical ventilation is excluded from considerations for energy efficient buildings as it consumes energy. It does. However: let us put this in perspective. A very efficient heat recovery ventilation system can have an energy load as low as 38 Watt (W) for a 125 square meter house. Assuming, the system is running on 200 days per year (24h), 182 kilowatt-hours (kWh) electricity are consumed. Efficient systems in Germany were measured! as having an average coefficient of performance (COP) of 16.5. For every kWh electrical energy consumed, 16.5 kWh heat were delivered. Compare this with the stated! COP of a heat pump!
But there is another interesting comparison. Electric blankets have an energy load of ca. 100W. Let us assume one blanket is used at 180 days per year for 8 hours: 144 kWh are consumed – to keep one person warm. As soon as another person in the household needs a blanket, the whole-house heat recovery ventilation system consumes less energy, while not only providing fresh air on 200 days in the year, but also doing most of the heating - at least in a well insulated and airtight building - keeping everyone warm 24/7! In addition, the system can also filter out noise and pollutants, and you do not have to worry about someone taking advantage of your open windows, when you are trying to get rid of excess moisture. Heat recovery systems proven to be highly energy efficient (via a 3rd party certification), are however currently not on the market in NZ. Or are they? My research in this regard was unsuccessful – but I would be pleased to hear otherwise!
Picture thanks to Qurren, under the GNU Free Documentation License.

Students at the University of Auckland were required to design details for Passive Houses in New Zealand climates in scale 1:1, plus: they actually had to build them! Here is an example of a window detail in a timber frame wall:


The challenge was to minimize thermal bridges and safeguard airtightness of all joints. Needless to say that the construction also had to be weathertight.




Design by Lin Ma.

Passive Houses do well in lifecycle analyses, as a range of recent research shows (please email me for references). Thus, it is nonsensical when some people demand not to build to Passive House standard on grounds that this leads to admittedly (slightly) higher embodied energy values than for a conventional building using the same principal construction method. Insulation - due to its light weight, typically only slightly impacts on the embodied energy balance of a house. When you are concerned about embodied energy, considering a timber building rather than building with concrete or steel will have much larger consequences than additional 10cm of insulation.
Another factor in this discussion that is often overlooked: Embodied energy in buildings is not lost, but largely only stored for future usage. Many parts of old buildings are already re-used, without much further energy input. Considering a growing resource scarcity, this will almost certainly lead to an increased asset stripping rather than simply putting demolition rubble on a landfill. Today's buildings can become tomorrow's hardware shops. Fossil fuels burnt today to heat houses, though, cannot be burnt again in the foreseeable future.
Picture courtesy of Markus Schweiss, protected under GNU Free Documentation License.

On 17 and 18 April, 100 speakers from around the world will convene at the 13th International Passive House Conference in Frankfurt/Germany, to present and discuss new trends, products and developments around passive housing. The conference will examine implementation of the Passive House concept in places like Korea, USA, Spain, Slovakia and many Scandinavian countries. As always, there is an accompanying exhibition, showcasing the latest in Passive Housed technology. See www passivhaustagung.de for more.

A forum was added to this website. It is intended as an exchange and debating tool for professionals. Everyone is free to look things up, but this is NOT the place to obtain general information about Passive Houses. Please continue to use the Questions? Comments? Button for this purpose instead.
All building professionals are cordially invited to register and join the discussion!