Passive house design for New Zealand.

Passive house design for New Zealand;
New Zealand really needs passive houses!

Passive houses, as defined by the standards of the passiv-haus institute, incorporate all of the energy-saving goals of eco-houses, straw-bale houses, green houses, solar houses, sustainable houses and others like those, in one comprehensive package and include additional measures such as a constant supply of clean, pre-heated air for the interior.

Christchurch, which at 18 October 2011 is estimated to need 45,000 new homes following the more-than 7,500 earthquake shocks during the last 13 months, and which has a cold damp climate in winter, is an ideal place for the use of passive houses.
As at the last week of November 2011, 6,000 existing homes have been declared unliveable because the land they sit on can not be stabilised enough. The subsoil of peat and sand is so liable to liquify in an earthquake that it can not be remediated / stabilsed enough to support essential services such as water supply, sewers, telephone and electricity. These 6,000 homes will be destroyed, the owners compensated by the Government, and the owners will need new homes elsewhere. This is a great opportunity for passive house designers in Christchurch and elsewhere to showcase passive houses in Christchurch, the South Island, and the world.

Imagine a new house in Christchurch which was never cold in winter, nor too hot in summer, AND which had a tiny electrical heating cost.

That is what a passive house will provide.

These pages give you a good ideal of the essential features of passive houses which make them so great.

The New Zealand Passive House Institute has details.

This site from the USA has even more.
(PDF file, 3.4 MB, 16 pages)

Links to pages about the seven precepts of Passive House design.


Very efficient Insulation

No thermal bridges

Air-tight construction

Great ventilation

Passive heating

High-efficiency windows

Passive solar gain

Important considerations

Early perceptions

Design standards


Winter or early Spring, in earthquake Paradise.

            Are you looking for designs for eco houses? Green houses? sustainable houses?

The passiv-haus = passive house concept embraces all these and more.

Recent articles in print media in Canterbury dealing with building standards and location have covered such matters as earthquake resistance, and community clustering.
Recently, there was the story about “The First Light House”.

In this article, the opportunity to make major gains in domestic energy conservation and in domestic comfort through house design and construction is explored. This is especially relevant not only because New Zealand house designs are particularly lacking in energy conservation considerations, but because electricity prices are becoming higher, seemingly at an increasing rate. Further, a significant percentage of our electricity is generated using fossil fuels, and it would be good to be able to reduce that component of our consumption.

By implementing a higher standard of energy management in domestic dwellings though design and construction, New Zealand could make considerable savings in electricity generation needs, both existing and new, which would benefit the Balance of Payments situation. New Zealand also typically has houses that are too cold for many climates, including that of Canterbury. New housing construction in and around earthquake-damaged Christchurch is a great opportunity to incorporate markedly higher standards than usual in this fresh housing stock. Such energy management could be applied to some commercial buildings as well. Building passive houses in New Zealand would solve these and other housing problems.

Consider two dwellings in the village I live in; Clyde, Central Otago.

The above shot is the view south from my house. The white stuff is common in winter.

Here are the two houses ...
The first is a simple one-bedroom home of 60 square metres floor area with single-pane glazing and no insulation. Heating is by heat-pump, which is kept switched on 24 hours a day in winter. A typical winter electricity bill in 2010 was $700 per month.
The next is a 5-bedroom house of 125 square metres, partly two-storied, with a log-fire, a night-store heater, and a heat-pump which was run only at night and additionally during really cold days. It has single-glazing, and pretty thin glass-fibre batts for insulation, possibly of ceilings only. Electrically, the most expensive three months were about $700. Wood for the good log-fire cost at most about $150 per month.
I believe that the experiences of these two houses are representative of very many houses all over New Zealand.

When I lived on Clifton Hill (Christchurch) in the 1980's, I remember we paid about $180 per month in winter, while houses on the colder flat land of Christchurch were paying about $400.

Yes, I know Clyde is probably colder in winter than Christchurch, but it is usually a dry cold, whereas that of Christchurch is often a damp cold that seems colder.
During these winter months, and this year it seems to be more than before, advertisements extolling the virtues of all kinds of heating appliances – conventional electric, heat-pumps, log, diesel, wood-pellet, and gas, are all over the media; and there are about as many advertisements for insulation, glazing enhancements, curtains, and heat transfer systems. These are all about increasing retail sales of commodities. None of them has ever provided for a complete and integrated system to effectively keep houses warm, adequately ventilated, and which seriously reduces heating costs.
That is, until the (passiv haus) or passive house system was developed in Europe.

This most exciting and promising method for home energy conservation and user comfort in respect of heat levels and air quality, contained in the so-called “Passiv-haus” system, was developed from collaborative research by Wolfgang Feist of Germany and Bo Adamson of Sweden with initial constructions in the early 1990's. A genuine passive house of the kind they developed is constructed to specific certified building standards written and maintained by the “Passivhaus Institut” (founded in 1996) in Germany.

To give some idea of what these standards are capable of, during 2005 a passive house was erected high in the Austrian Alps. Actually, it is an alpine refuge with 70 beds; the Schiestlhaus or Schiestl Hutte, at an altitude of 2154 metres a.s.l., under the summit of Hochschwab. Satisfactory living temperatures with good atmospheric conditions were maintained in it during the winter from the body heat of the occupants, heat gathered from 46m2 of solar collectors, and sometimes a solid fuel heater. See THIS wikipedia article written in German
and see This American article which contains some pictures
The Schiestlhaus uses passivhaus principles to keep people warm, but in Lisbon, in Spain and in Florida, the same principles are used to keep the interiors of the buildings cool. The Passiv-haus Institut has altered the design criteria to suit a hot climate.

Imagine the energy savings that such construction could bring to a house in New Zealand! And such energy-controlling standards also minimise unwanted heat-gain in summer, since the transmission of heat in a passive house is a bi-directional matter.

Contrast the New Zealand costs below with what a passive house would cost.

To be certified by the Passivhaus Institut a passive house must consume less than 15 kilowatt-hours of electricity per square metre per year for its heating and cooling, with total energy consumption for all heat, hot water and household electricity that doesn't exceed 120 kilowatt-hours (kwh) per square metre per year.

In October 2010, in the 5-bedroom house, we were charged 25.5 cents per kwh for the "anytime' cost. Other components such as water heating cost less, but the "anytime" components were by far the major part of the bills.

A certified passive house on this cost regime would have cost no more than $3.825 per square metre for all heating and cooling for a whole year, and $30.60 per square metre for all electricity usage combined.

Our total electricity bill for a whole year from May 2010 was $2986, and the actual cost of firewood used during that year was $1300; but the energy gained from firewood is maybe twice the amount per dollar than that from electricity, so the electricity equivalent cost of the firewood was about $2600. Therefore the total cost of energy used for the year was about $5586.

The house area is 125 square metres, not counting the double-storied part twice. A passive house of this floor area should cost no more than $478 for heating and cooling for the whole year, and $3825 for all electricity for the same period, or 68.5% of the actual cost.

Furthermore, seldom during winter could the whole house be considered cosy; usually we wore plenty of warm clothes, and bedroom warmth at night of around 11 deg C on a warm night was a real consideration especially for the oldest residents who are in their 70's. It is well known that for the health of small children and for older adults, house temperatures should be at least 18 deg. C. To attain a temperature of 11 deg. C in those conditions required the use of supplementary heating such as a vertical thermostat-controlled electric fan heater, and good electric blankets on the bed.

It is interesting that a recent edition (July 2011) of the Otago Regional Council brochure “Airzone” recommends using heat pumps to warm only the space currently in use; no doubt because of the high cost. Passive houses have no such limitation. The whole house is kept warm as one unit.

It should be noted that over recent months, electricity retailers have been replacing old electricity meters on domestic houses with new models. Many people have noted that their monthly electricity bill has markedly increased following this swap. It seems that the older meters gave quite conservative readings, and this has implications for calculating thermal efficiency in New Zealand if old data are included.

A study conducted in Germany in 2003 compared the energy consumption of passive houses with the energy consumption of both conventional and energy-efficient homes and found that passive houses had an average energy savings of 90 percent over conventional homes [source: Passivhaus Institut].

One report sighted claimed that one towel rail was sufficient, along with heat recovery from exchanged air, to heat a house.

To meet the passive house certification standard established by the Passivhaus Institut, homes must be built to specified possible modern standards, making for a durable, well-built home. Because every aspect of the passive house is carefully planned and specified in advance, there is theoretically little room for error in the building process, and nothing is left to chance with regard to materials or construction. Many of the interior and exterior finish materials used in passive house design, such as the high-end windows and doors, are virtually maintenance-free. Would building to such high standards be a difficult challenge to New Zealand builders these days?

This two are not passive houses, but are in Clyde.

How does a dwelling constructed to Passivhaus standards achieve the energy savings?

Michael Cockram, an architectural designer, educator, and writer, wrote:-
“To qualify for certification a building must meet three basic criteria, which are the same for all projects, regardless of location or climate: annual energy consumption for heating and cooling is limited to 4,755 Btu per square foot ( 15.0 kwh/m2 - Ed.); air infiltration is set at a maximum of 0.6 air changes per hour at 50 pascals of pressure; and annual primary energy usage (energy consumed by appliances, lighting, and other devices not directly related to heating and cooling) is capped at 11.1 kilowatt hours per square foot ( 119.480 [120.0] kwh/m2 - Ed. ).”

The degree to which the design of a house meets the Passivhaus standards, the thermal characteristics of the materials used ( material, thickness ), the joining methods, active heat management systems and the air-tightness of the house design are all fed into a computer program which calculates the ability of the house to retain either heat or cool condition (depending on whether it is testing for summer or winter conditions), and compared with the standard for that size of house. Air-tightness of completed houses is tested with an air-pump.
The data for the graph below came from a careful study by an architectural company of a house in Vermont.

Beth Brindle, in "10 Benefits of a Passive House" 28 March 2011. 04 April 2011; wrote (this quote has been amended by addition);

Characteristics of a passive house include the following:
  1. Heavy insulation: The most important component of a passive house is a layer of highly efficient insulation that wraps continuously around the building envelope -- even beneath the concrete slab in the basement -- reducing heat transfer between indoor and outdoor spaces [source: Passivhaus Institut].
  2. Design without thermal bridges: The heated air inside a house will follow the path of least resistance to the outside of the house, known as a "thermal bridge." Conventional homes offer plenty of them, in the form of inefficient windows, poorly insulated walls or cracks under doors, but passive house design eliminates them through superior insulation and efficient windows and doors.
  3. Airtight construction: Passive houses feature airtight construction to prevent moist room air (or humid outside air, in warmer climates) from penetrating into the home's construction where it can cause mould, affect inside air quality and even cause structural damage. This construction also prevents the most common cause of inadequate heat conservation; draughty gaps letting cold air enter from outside.
  4. Ventilation: Another important component of passive house design is its efficient central ventilation system, which continually exchanges moist, "polluted" inside air for fresh, filtered outside air to maintain a comfortable, consistent temperature and humidity level.
  5. Passive heating technology: Perhaps the most ingenious part of the passive house concept is its ability to heat (or cool) the inside spaces with nothing but fresh exterior air. As fresh, cold air enters the house through the ventilation system, it is heated by the warm air it passes on its way out. Some systems have the incoming air passing through subterranean heat exchangers which extract significant heat from the ground.
  6. High-efficiency windows: Efficient windows are essential to the passive house design. The specific windows used vary from climate to climate, but triple-paned windows with low-e glazing, argon gas and insulated frames are common.
  7. Passive solar gains: Passive solar gain -- that is, the good old warmth of the sun -- is the primary source of heat for a passive house, so the situation of the home on the lot and the size and position of windows are important factors."

Wall insulation can typically result in walls that are about 500 mm thick, which is less than for straw-bale houses, but still within an acceptable range. Floor insulation, where houses are built on concrete platforms, is also thick, but will be out of sight. The most difficult part to insulate adequately is at the bottoms of exterior walls, so these require extra measures. Avoidance of thermal bridges means that no structural elements will span from the interior wall to the exterior wall. This applies also to windows. Typical aluminium windows in New Zealand have frames with connected edges exposed to both exterior and interior air and temperatures. Such window-frames can not be used in a passiv-haus.

Typically, the ceiling space of New Zealand houses is a draughty place where it is not too difficult to find spots where the sky is visible from inside. Not only must all such gaps be eliminated in a passiv-haus, but also all draught gaps around doors and windows. Draughty walls are out! It is imperative that the air exchange is under tight management with mechanical or electronic control when the house is in use, except when the occupants choose to open doors and windows.

Passiv-haus techniques can be applied to existing houses by making improvements to the insulation and air tightness, replacing existing windows with high-efficiency windows, and modifying the existing duct work to accommodate the passive house system of heat recovery from exhaust air, sufficient to achieve passive house certification. [source: Feist].

One of the most satisfactory aspects of Passivhaus designs is that it is not too difficult to make them look like many conventional modern designs; in other words, aesthetics are not necessarily constrained by superior energy management techniques and construction.

However, as I write this, I note that many designs for passive houses are visually boring and mentally stifling. What really made me sit up and take notice of this was the designs for an Auckland group housing project by Professor Uwe Rieger. Each of the 19 units is like a trapezoidal box, and they were essentially all the same !!. There wasn't even ONE roof to be seen! How utterly boring ! Architecture has a vital place in society which is to uplift the human soul by feeding it pleasure and inspiration through visual input.

When I saw these I was reminded of the 1962 song by Malvina Reynolds which covers this. I know that passive houses are not made of ticky-tacky, but the feeling is there. Architects can and should do better; a lot better.

(TO COME photos of two passive houses)

Passive houses are noted for their ability to deliver better health for their occupants through providing a much more healthy temperature, especially where the climate is extreme; especially in New Zealand, extremely cold in winter. For this reason alone, it would make a lot of sense for many more passive houses to be built in New Zealand.

However, one positive aspect of passive houses that seems to have been completely ignored in the writings I have seen, is the ability of passive houses to deliver clean filtered air to the occupants.

In the parts of New Zealand where it is cold for 4 - 5 months of the year, people tend to use enclosed log-burners to provide heat. Log fires are attractive, because the cost of electricity is so high. Where I live, just 1 km from a hydro-electric power plant, our electricity prices are amongst the highest in New Zealand. So, of course we have a log fire.

The downside of log fires, in most of the cold townships and cities in southern New Zealand, is air pollution. When I was younger, I used to scoff at the suggestion that this made people ill. Now, having gained a few years, I can attest to the fact that the pollution makes me quite ill; headaches, congested sinuses, sore eyes. And children get asthma from it. From May to September, between the hours of 10 pm to 3 am, the outside air where I live is absolutely putrid. It not only stinks, but if I let it into the house, it makes me ill within 5 minutes of exposure.

Passive houses deliver filtered air to the house interior. I have not experienced this myself, but can imagine this to be effective if the machinery has the appropriate specifications. As far as I am aware, none of the businesses retailing electrical contraptions to make houses nicer to live in, advertise or provide workable bulk air house filtration. In my opinion, designers of passive houses should make more of this feature.

I do not believe that the efforts by Regional Council to clean up the air will be adequate to solve what is a significant problem for me, and I suppose, others. Had I known in advance how bad the problem is here, I would never have bought a house here.
To implement Passivhaus designs, architects will have to learn new skills. But perhaps the people who might face the steepest learning curves will be the managers of building companies who might find the opportunities for short-cuts are rather limited if the standards are to be met, and the tradesmen who may need to learn new standards of following plans and precision construction, for the same reason.
Architect Ulla Janson, in her dissertation at Lund University, noted that it was important to get all people involved in the construction "on side". This means that there should be time set aside before the beginning of construction to tell and show tradesmen and contractor principals exactly what the goals are. Professor Uwe Rieger of Auckland, writing about a project he worked on for Auckland City, showed how he used mock-up panels and portions of detail, for instruction. He further suggested that passive houses should be essentially modular, with the modules fabricated off-site in a high-precision work-shop, and assembled on-site. This makes a lot of sense, since it takes away from the influence of possibly wrong-motivated contractors and tradesmen the task of conscientious construction out in the open in all weathers, and places it in the hands of workers who potentially have different and more precise skills, and in a controlled environment where inclement weather should have no influence on the excellence of the construction of the components.

Of course this approach of having modules constructed off-site in specialist cabinetry workshops may not be applicable in the beginning, or in places where only very few passive houses are to be built. However, such businesses as those which fit out shops or make kitchens could perhaps be persuaded to add to their skills.

And that reminds me of the ability of Lockwood Homes (Rotorua) as far back as the 1970's, to pre-cut, to a high degree of precision, all the wall and ceiling components of a house. In this way, they were able to deliver a truck and trailer unit containing all of one house to building sites all over the North Island. If they could do it then, why not now, for passive houses?

Is the industry up to the challenge?

A consequence of building a genuine Passiv-haus is that it is a well defined product, understood by the developer, architect and owner; everyone involved in the process knows what they are getting.

Costs; while it costs more to build than a current standard house, according to Rob Harrison of Harrison Architects, the cost premium can range from 3, 5, 7 to 20% above “normal” in NW USA. He writes that “assuming a ten per cent premium and a conservative one per cent per year increase in energy costs, the investment in Passivhaus pays for itself within ten years, and thereafter earns money for the building's owner.”

In addition to awarding its "Quality Approved Passive House" certificate to qualifying homes, the Passivhaus Institut offers a "Certified Passive House Designer" certificate to individual architects, builders, engineers and others who pass an examination or complete an approved passive house construction project. According to there is one certified Passivhaus architect in Christchurch and two in Otago, as well as others in New Zealand. The website has it that these are the only such qualified architects in the Southern Hemisphere.

Are passive houses worth the extra effort? Would it be worth while to build a passive house in New Zealand? Many estimates demonstrate that all these stringent requirements, tests and certifications pay off very well: Passive homes provide, on average, energy savings of 90 percent over conventional homes and up to 80 percent compared to homes built to modern European standards for energy consumption [source: Passivhaus Institut].

Glenn Murdoch at Wanaka, is a major designer of passive houses.
AS of May 2012, Glenn has an office in Christchurch, so is readily available to create sustainable, healthy, warm and economic houses to replace homes for earthquake victims. which converts to at 229 Kaikorai Valley Road, Dunedin. Tel; 03 453 0340, contact
Does double and triple glazing in durable timber frames which avoid thermal bridging (heat conduction between the interior and exterior of the house) by the window frame components.

Written by Brian Swale at bj (at) caverock . net . nz

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