Passiv Buildings

Passive House, or the German Passiv Haus (PH), is a tried and true performance standard for the construction of buildings which use very little energy to heat or cool them. This standard is not to be confused with designing a house which uses passive solar gain to heat a house. Rather, the focus is on designing a building envelope which suits the local climate, specifying windows and doors which meet the criteria for certification and eliminating thermal bridging from the building envelope.

“Passive houses are defined as buildings which have an extremely small heating energy demand – they are kept warm ‘passively’ solely by using the existing internal heat sources and the solar energy entering through the windows as well as by the minimal heating of incoming fresh air”. (Passipedia, The Passive House Resource).

The Passive House Institute was founded in Germany in 1996 by Dr Wolfgang Feist. The first pilot project was the Kranischstein Passive House in Darmstadt Germany 1990. This was Europe’s first inhabited multi-family house to achieve a documented heating energy consumption of below 10 kWh(2a). This is less than 20% of the energy that would be used for heating in a house built to the New Zealand Building Code.

The wonderful thing about the Passive House tool is that any building can be made ‘Passive’. Schools; indoor pools, offices and existing houses can all be built to be Passive Houses. In fact ‘haus’ in German just means, literally, ‘building’. The Passive House system is particularly beneficial for those in our community who struggle to meet their energy costs.

Some of the benefits of the Passive House are:

  • There is absolutely no possibility of damp or mould growth within the house
  • A PH building stays at a constant temperature throughout the year and there is little difference between summer and winter, day and night
  • The air quality is excellent and there are only very small variations of internal ambient temperature. This means that there are no cold/hot spots to annoy the occupants
  • PH houses are quiet!
  • The up-front costs are easily absorbed over the life time of the building
  • Through the PH Planning Package software and the use of blower door testing, building performance is guaranteed
  • PH principles can be applied to any style/any construction of building.

The process

  • Find a Passive House designer – www.phinz.org.nz
  • The PH designer will work with an architect (sometimes an architect will be a PH designer). The PH designer should be engaged at the very earliest stage of the design process
  • The envelope and the site have to have their potential maximized by careful consideration of the local climate. PH considers NZ to have 16 climate variations compared with the three that the Code specifies. Thermal bridging from the exterior to the interior should be minimised by a careful consideration of junctions and the materiality of the fabric of the building
  • High quality windows, doors and wall structures are specified.
  • A highly efficient heat recovery system is designed.
  • Once the envelope is closed, a blower door test is conducted to ensure there is no building leakage
  • The building will be put forward for final certification once it is certain that the building meeting airtightness standard and the contractor confirms that it was built in accordance with the design.
  • The design will then be certified by another PH professional.

At the recent COP 23 held in Bonn – The UN expressly mentioned Passive House buildings as a way to achieve significant energy savings in the building sector (visit www.passive.de for more information). Given that building/construction is the largest carbon producer in the world, it is important that buildings are built for longevity. As Enrico Bonilauri said at this year’s South Pacific Passive House Conference, if you build a house to a low standard, you are locking in energy inefficiency for decades to come.

The lucky few who live in Passive Houses in New Zealand rave about them. Check out www.phinz.org.nz for a list of certified Passive House designers in your area.