Earlier this month BRE organised a three-day study trip to Hanover during which delegates learnt about the principles of a super-insulated, low energy form of housing known as PassivHaus. Places sold out over night and a second trip planned for early Spring was booked up just as quickly.
The reason for all this interest was timing. At the end of 2007, Communities and Local Government (DCLG) launched the Code for Sustainable Homes (CSH) which sets more stringent requirements for environmental performance than its predecessor EcoHomes.
The PassivHaus principle is currently one of the most energy efficient approaches to designing, specifying and constructing practical housing. Originally developed in Germany by the PassivHaus Institute, it fuses into one standard the successful principles demonstrated in experimental buildings constructed in the late 70s and early 80s by low energy housing pioneers such as Amory Lovins, William Shurcliff and Vagn Korsgaard. To date over 6,000 dwellings have been constructed to the PasssivHaus standard in Europe, with the concept being tested and proven in terms of energy savings, functional viability, economics, indoor air quality and occupant satisfaction.
The concept is recognised by many influential organisations including the Energy Saving Trust and the Association for Environmentally Conscious Building as a pathway towards zero carbon housing. It provides a framework which could help UK designers and house builders to maximise the CSH energy credits cost effectively, whilst also producing exemplary standards of health, comfort and air quality.
Homes built to the PassivHaus principles can achieve up to a 50% reduction in carbon dioxide emissions compared to current UK new build housing without the addition of renewable technologies. The key components are very good levels of insulation with minimal thermal bridges, very high thermal performance windows, well thought out use of solar and internal gains (including the avoidance of summertime overheating), excellent levels of airtightness, and a whole house mechanical ventilation system with highly efficient heat recovery.
Reduced capital costs
The PassivHaus principle is based on Amory Lovins’ concept of tunnelling through the cost barrier by reducing capital costs through energy efficient design.
By dramatically increasing the energy efficiency of a building, via the above steps, the heating systems can be radically simplified, with the capital and maintenance cost savings offsetting the cost of installing high levels of insulation and ultra-high performance glazing.
When these features are specified in the design, traditional heating systems are not required. What little heating is needed can be met using either a small in-duct heater within the ventilation system, a group heating system or other small low-carbon technologies. This means that carbon dioxide emissions can be reduced without dramatically escalating build costs. The savings in the cost of installing and maintaining a central heating system pays for the higher thermal standards.
The PassivHaus approach requires designers, specificiers and contractors to work together in an integrated manner from the outset of a project, so it is important that all members of the supply chain buy into the concept and understand the need to undertake quality control checks during design, construction, commissioning and handover. It is also essential that occupants understand how their PassivHaus homes work and are shown how to run and maintain them.
The interest and enthusiasm shown by everyone on the study tour was quite overwhelming, according to Neil Cutland, BRE Housing specialist. ‘We definitely got the feeling that people were going away thinking, Yes this works, it’s practical and can be replicated in the UK.’
Two points in particular seemed to impress. Firstly the excellent air quality within the houses. Given the levels of super-insulation, many had expected a slightly stuffy atmosphere. But the ventilation system, which is virtually silent, is kept running all the time which means you never feel you have to open a window. And because this system incorporates a heat recovery heat exchanger, in colder weather the fresh air is already comfortably warm when it enters the living areas.
The other issue that made an impact on delegates was the flexibility of the PassivHaus look. It is not a prescriptive approach, so designers can chose the style they want whether this is cutting edge modern, comfortable mainstream, stockbroker belt mansion or city high rise apartment block. The principles can even be used for refurbishment projects where a standard very close to PassivHaus can be achieved given the right starting point.
The 72 delegates who attended the study tour represented most sectors of the housing industry and included high ranking officials from the Treasury, Communities and Local Government and Defra. The projects visited demonstrated the success and adaptability of this very practical approach to ultra green housing. There was confidence that the PassivHaus could serve as a blue print that would help the UK housing industry to achieve the very challenging levels 5 and 6 of the Code for Sustainable Homes.
The PassivHaus Planning Package is available in the UK now and a further study tour to Hannover being planned for May.
http://www.passivhaus.org.uk
Figure 1: Space heating requirements based on a large detached dwelling of 144m2
