It seems to me that, in broad terms, other systems of building houses aim to do better than what are
delivered by traditional builders and spec. builders. However, in general they concentrate on ONE feature
of the house construction, and other important performance components are often poorly integrated into
the total package.
Straw Bale Houses:
The main idea behind these is that straw bale walls give super wall insulation. Especially when compared with the traditional New Zealand construction of ship-lap timber cladding over building paper on 4 x 2 timber studs and minimal fibreglass insulation.
There is no doubt that straw bales give excellent wall insulation, and there is another bonus; they get people used to the idea that well-insulated walls probably will be somewhat, or even a lot, thicker than people are traditionally used to.
However, there is no integrated system to control air-leakage or ventilation, bales are a one-size-fits-all solution which can not be tailored to the temperature regime of the region of use, It doesn't address the topics of thermal bridging, roof insulation, floor insulation, total energy requirements, and passive solar gain, to name seven.
The main objective of this design path is to use photo-voltaic cells and battery systems to power the house, and solar water heating to provide hot water. This concept, as for straw houses, does not intrinsically address the other seven vital components that should be integrated into a house. The expertise they use is awesome, and should be useful for passive houses.
The core design proposal behind these houses is rather similar to that of straw houses, but in addition they promote the idea of the strength of mud-brick walls for internal as well as exterior walls. How these can be rated for compliance with earthquake-focussed building code requirements, I have no idea.
As far as I can tell this concept does not include, as a matter of course, other the design elements which will provide a low-energy-cost and healthy home.
The main thrust of this design concept is to have the least possible impact on the environment through building the house, and places emphasis on avoiding "toxic" components.
They do identify some poorly known hazards associated with painting systems.
The Passive House system, in comparison:
Has all the important requirements for a house to be insulated all around, heat-conserving, adequately and steadily filtered-air ventilated by an automated system, not draughty, with no thermal bridges, gathering passive and solar heat where possible, using timber ( the world's most sustainable raw material ) wherever possible, high-efficiency windows; these characteristics are ALL incorporated in a certified Passive House design in such a manner that they work in harmony. The physicists / engineers who wrote the simulation / evaluation package that is required to be used, are able to predict precisely how the house will perform, because the heat transfer rates / conductivity, ventilation speed, and all such factors ar all known and therefore the amount of energy needed to be imported can be predicted. If owners want to add green roofs, composting toilets and so on, these components can be factored in.
No amount of experience can compete for accuracy of prediction with a good simulation program based on fact. The program used by the Passive House Institute, named PHPP, is a Microsoft XLS spreadsheet file, using verified physical values for such as R value, U value, and so on.
See this paper from Germany which gives some idea of the benefits.
Would you like to see a passive house in New Zealand now?
You can follow the blog of the first build at
New Zealand's first Passive house blog-spot
This house is now completed and the happy owners are using it.
Read about it at this Auckland newspaper site Well done !!
Another NZ passive-house is documented on-line, on facebook. If you are a facebook user, you should have no problems viewing these pages.
A New Zealand Passive house set of informative pages
A New Zealand Passive house - the base page
Congratulations to Brooke the Architect (MOAA Architects) for what looks like a thorough job, and likewise the builder for following instructions so well. Lots of construction detail in here.
View an Irish video - 11 minutes long - on passive houses
Passive houses in Ireland here.
The amount of energy needed to be purchased for heating is greatly reduced in comparison with conventional homes. In addition, it is much easier to maintain house internal temperatures at healthy levels, as compared with many older New Zealand homes which notoriously run in winter at temperatures so low, that, as many health studies have shown increased sickness and mortality of older people and the very young result.
In passive houses the whole house (not just those rooms being occupied for the moment) has its heat level maintained at the saome temperature, and clean air is likewise supplied throughout.
Passive houses result in healthier families than other kinds of house design do.
A passive house in New Zealand could not use a normal [ as at 2011 ] log-fire because the heat output is too great. Smaller fires can be imported. Likewise, a normal heat pump could be useful to provide initial warmth for a house in winter if it has been vacant for a while, but after that it would not be needed. In cold weather, the left-over heat in the air arising from cooking, showering, refrigerators and human bodies, extracted from the exchanged air by the air-supply system, will mostly be enough to provide a very comfortable living temperature.
Links to pages about the seven precepts of Passive House design.
Very efficient Insulation
No thermal bridges
Passive solar gain
Prices / costs