The Passive House

A home with almost no energy bills?

From the outside, Passive House homes look like any other. This apartment building is built to Passive House standards and is part of the Vauban community, on the outskirts of Freiburg in south-west Germany.

It might seem impossible to some but clever house design that virtually eliminates ongoing energy bills is possible and happening in some parts of the world. The concept has been most vigorously developed in Germany and is known as passivhaus or in English, Passive House. The first demonstration model was built in Germany in 1991. Homes of this type look like any other; the features that make a home a Passive House generally are not that visible either inside or out.

A Passive House includes passive solar design to optimise the sun and many other clever features that all work together to keep the internal temperature as constant as possible:

  • * Seals between all joins such as between walls, floors and the roof, making the home draft-proof  and airtight.
  • * Thick insulation that fits snuggly across connecting parts, with thickness relating to climatic variations of where the home is situated
  • * Effective ventilation with a near-constant indoor air temperature using heat recovery via an energy recovery ventilation system
  • * Elimination of any thermal bridges where materials transfer temperature such as occurs across a single paned window
  • * Insulated window frames (preventing any thermal bridging) with triple glazing

passive house

To prevent any air leaks, the external walls are taped wherever different materials and components are joined. Taping is also done around points where electrical wiring etc. is penetrating the external wall such as for lighting and power points.

Passive Houses require very little additional heating or cooling compared to more conventionally constructed homes — usually 90% less energy is required. Imagine being able to do away with air-conditioning and heating bills. In a Passive House this is almost possible. As with any house, the behaviour of the occupants plays the biggest part in how high or low energy bills are.

So what makes a house passive? It’s about optimising the passive rather than active methods of heating and cooling. For example, the insulation combined with the air seals of a Passive House are so effective that there is limited cold air entering from the outside or any heat being lost from the inside. In a way the home is like a thermos, or insulated flask: body heat and perhaps an appliance or two are generally all that is needed to keep its occupants at a comfortable temperature when it’s cold outside.

A unique and not commonly seen (in Australia) component of the Passive House is the ventilation system that uses heat recovery. Heat generated in the home is directed to the energy recovery ventilator, mixed with fresh air taken from outside the home, then circulated back inside. Unpleasant odours are extracted by the ventilator and emitted outside of the home.  A constant supply of warmed fresh air is available. The energy recovery ventilator is low in energy use and quiet. A heat pump can be activated if more heat is needed.

passive house

Ventilations systems of Passive Homes are unique. This picture shows the air exchange outlet/inlet which will be in every room of the house. This works together with the energy recovery ventilation system to supply constant fresh air at a comfortable temperature.

What about when it’s hot outside and you want it to be cool inside? The heat pump operates as an air-conditioner as well — despite its name it can cool air as well as dehumidify.

Thermal bridges occur when one material allows hotter air to move to an area with cooler air. Eliminating thermal bridges is essential in a Passive House. Thermal bridges occur in homes in many places; for example, fastenings like bolts or studs that penetrate from external walls through to internal walls act as thermal bridges. Thermal bridges can also occur at aluminum frames of windows that aren’t insulated. Eliminating thermal bridges is done by insulating, or using different construction methods.

Homes must meet stringent quality requirements to achieve Passive House standard. Tests are carried out at certain points to ensure such things as effective air seals are in place. Training to obtain qualifications in administering Passive House standards is available in many parts of the world.

Although popular as stand alone homes, Passive House design principles can also be applied to apartment buildings. Pictured here is the Klima SolarHaus in Berlin, Germany. It was the first apartment complex to be built to passivhaus standards in Berlin. It was completed in 2009 with 19 separate apartments on a north–south axis.

Older homes can also be renovated to achieve Passive House standards. Installing features such as those mentioned previously is required. A cost-benefit analysis approach could help you work out whether the costs of undertaking the works would result in sufficient benefits and savings of health, comfort and energy costs.

In the part of the world where the Passive House concept was born and is growing in popularity, the winters are much colder and the summers much milder than is experienced in most of Australia. However, areas like Tasmania, Melbourne and those just west of the Great Dividing Range such as Canberra could benefit from adopting the Passive House approach to home design given the similarities of these climatic areas to those of northern Europe.

passive house

The Klima SolarHaus apartment building in Berlin, Germany is the first apartment building complex to have been constructed to Passive House standards in Berlin.

Many parts of Australia experience high levels of humidity and this is a challenge to the Passive House. As explained by John Quale, author of Trojan Goat: A Self-Sufficient House, humidity is a concern. “Given the Passive House is so tightly sealed, if there was to be any areas where moisture was to enter, as we know any hot air will want to move to colder air, it will migrate to any gaps that it can find. Once it finds that gap, if this humid air finds wood or some other natural fibered material, mould can grow there. Obviously you don’t want that to happen so you have to make it even more well sealed. The normal home builder might not know that.” Qualified Passive House practitioners have designed and constructed Passive Houses in humid parts of the United States.

Part of how a Passive House maintains a regular temperature is through the home remaining sealed, so with our love of integrating indoor and outdoor living it’s likely that the Passive House methodology and construction might need modification and adaptation to suit the Australian climate and lifestyle.

Wherever you live, there are many elements and design principles of the Passive House standard that can inform how you build or improve your home.

Source: For more information including a detailed guide see the Passive House Brochure, released by the International Passive House Association

Our Guest Author

Imogen Schoots is our traveling correspondent. During her travels, throughout Asia, Europe and Northern America, Imogen has provided Liveability with updates on what she sees, hears and learns about living life sustainably.

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