The construction industry has had to get used to so-called passive house design in recent years. The principles behind it have taken off in Australia, just as they have in Europe and North America. Essentially, the thinking behind a passively designed home, office structure or public building is the same.
These new buildings should not rely on ongoing energy consumption to either cool them in hot weather or heat them during winter. This poses certain challenges for the construction sector which has had to learn how to adapt to this new style of architectural design and engineering.
Despite this, many construction firms have embraced this style of building, seeing its value for the environment in the long-term. What construction methods are needed for a passive house?
A thermal bridge is something that is common with conventional building methods. Heat that is trapped inside a building during winter should be kept in place so that losses are minimised. Often heat will escape from a building via a thermal bridge. A good example of this is where a window frame acts as a 'bridge' between the outside and the inside. Installers need to fit materials which have been tested to provide the least thermal coefficient that they can, for example with thermal inserts placed inside aluminium window and door frames.
Keeping the baking Australian sun out of a passive house is just as important as trapping warm air inside in winter. Therefore, roof insulation products should be fitted not just in the loft cavity but right up high in the roof purlins. Thermally resistant products can usually be cut to size on site and fitted prior to roof tiles being laid. Alternatively, some prefabricated products can be obtained for buildings which have a specialist design, such as flat-roofed homes. The key is to block heat transfer vertically, where most of the losses are to be found, as well as preventing the roof from acting like a heat absorber in summer, warming the rooms below to an uncomfortable level.
Heat Exchange Ventilation
One of the keys to a passive house's reduced energy usage is that it will be cooled naturally by outside air. Since hot air rises, ventilation systems should be placed high in the home's rooms such that heated air can escape. With good design, flues connected to the outside should draw external air to where it is most needed, thereby reducing the internal temperature. Heat exchange systems usually need to be installed in larger construction projects for this approach to work efficiently.