Introduction - Passive House buildings in different climates
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Introduction - Passive House buildings in different climates

The principle remains the same - the details have to be adapted.

This statement can be taken as the general rule governing the design of Passive House buildings in all climates around the globe.

Passive House buildings: a method rather than a building style

In Central European Climate there is a lot of practical experience on how to build Passive House buildings. But it would be a pitfall just to apply the Central European Passive House design, especially the details used for insulation, windows and ventilation and just copy these to a completely different situation because

there is a specific building tradition in every country and

there are specific climatic boundary conditions in every region.

Therefore, the specific solution for a Passive House building has to be adapted to the country and the climate under consideration.

On the other hand: The goals are the same in all climates and for all countries. Also, physics is the same all around the world. So the problem to build almost self sufficient houses (i.e. Passive Houses) is well defined. The physical equations are the same - only the boundary conditions vary. Thus the solution method can well be applied independently of the circumstances in order to find the appropriate way of Passive House design in a specific country and climate.

Passive house buildings: The functional definition

It is a lucky coincidence: Although the specific design of passive houses may look quite different in varying circumstances, the leading principle will be the same. This principle has been derived from Amory Lovins' idea of reducing the investment by using a more energy efficient design, going that far with efficiency, that there will be a certain breakthrough to radically simplified technology.

For the case of heating or cooling, this means to radically reduce the peak load by means of insulation, heat recovery, highly insulating windows, passive solar design and other measures. When the peak heating load reaches the value of 10 W/m², independently of the climate, the ventilation system may easily be used for heating. No other heat distribution system than just the air supplied for excellent indoor air quality is required any more.

Thus, the definition of a Passive House building basically consists of limiting the peak heating load to 10 W/m². In some climates that may be easy to achieve; in other, colder climates it may be more difficult.

And the same applies for cooling: Passive measures are to be chosen to reduce the peak cooling load: proper size and quality of windows and shading and the reduction of the internal heat loads by using highly energy efficient equipment. Again, the remaining small amount of cooling energy which might still be needed can be delivered by cooling of the fresh air supply required for good indoor air quality anyhow (see Passive Houses in South-West Europe as a exemplary solution).

Practical hints

Looking at the heating load is just an example. In many locations other energy services such as cooling or dehumidification are much more important. Again the method to determine a Passive House will be the same: Peak loads are limited until an appreciable simplification of the active technology needed for cooling / dehumidification can be achieved.

Some rules of thumb which are valid for all climates:

You should keep comfort at a high level. Passive Houses should be well known as the most comfortable houses - in any country and within any climate. Be aware that all persons would like to live in a comfortable indoor climate and that all of them should have a right to do so. Therefore, in the long run, no solution will persist which will not contribute to a better indoor climate.

The solution should be simpler than ordinary buildings/systems used so far. Only affordable solutions will be attractive in a competition with conventional technology like standard air conditioning.

It is not necessary that the solution will not need any conventional energy demand ('zero energy solution') - that might be very expensive. It is sufficient to use a lot less energy than in ordinary systems. At a factor of 4 to 10, the energy conservation is likely to be high enough to pay for the extra efforts needed.

Insulation might be a good idea in all climates.

Shading will be absolutely necessary in all climates with high solar radiation during Summer.

Heat recovery will be necessary in all cold and in all hot climates. If the houses have a ventilation system, which will be a good idea if external temperature will be lower than 8 °C or higher than 32 °C in a relevant time period, the supply air ducts may well be used to transport heat during the heating season, cool air during the hot periods and dry air to dehumidify if necessary.

Using very low amounts of auxiliary energy is an important precondition for passive solutions. The fans in ventilation systems, for example, must use highly efficient electronically commutated motors. This is obvious in the case of recovery of cooling energy, but it is necessary in systems for heat recovery, too. On the other hand - don't hesitate to use a ventilator; moving air requires much less energy than heating or cooling it significantly.

In many cases the ground can be used as a heat or cold buffer. Vernacular architecture in a country may indicate whether ground coupled systems are an opportunity. The traditional solution may be very expensive, however - like huge air channels or earth buried houses; that will not be a solution reproducible for the future. But there are less expensive solutions using modern technology like earth buried ducts or ground probes.

Technical and economic aspects

Preliminary requirements for residential Passive Houses in all climates worldwide were derived from the technical and economic considerations. These requirements concern indoor heating, sensible and latent cooling, airtightness and primary energy demand. The criteria for primary energy demand and airtightness remained the same worldwide. Read more...

References

[Feist/Adamson 1989] Feist, Wolfgang; Adamson, Bo: Design of low-energy houses in the federal republic of Germany; Lund University, Report BKL 1989:3(E)

[Schnieders 2009] Schnieders, Jürgen: Passive Houses in South West Europe — A quantitative investigation of some passive and active space conditioning techniques for highly energy efficient dwellings in the South West European region. 2nd ed., Passivhaus Institut, Darmstadt 2009. http://www.passivehouse.com

[Schnieders et. al. 2012] Jürgen Schnieders, Jürgen; Feist, Wolfgang; Schulz, Tanja; Krick, Benjamin; Rongen, Ludwig; Wirtz, Reiner - Passive Houses for different climate zones, Passivhaus Institut, Darmstadt Nov. 2011 order via www.passiv.de

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