January 2011
Energy use in our society is almost always associated with pollution and habitat destruction so all types of energy use are worth looking at:
- While a house is being built
- reducing embodied energy of the building materials
- reducing associated 'building site' energy
- During its lifetime
- Upon demolition
Where can the biggest savings be made?
Undoubtedly the main savings are to do with while the house is in use (rather than during construction) and are mainly related to heating and lighting. Particularly the heating and fixed lighting are important because, especially with the heating, it is very difficult to increase the insulation values of the structure after it has been built. It may last for hundreds of years in basically the same state that it was built originally. Items such as electrical appliances and movable lighting are important but tend to get changed every decade or two.
The embodied energy is often cited as being much less important than energy in use (sometimes mentioned as being very roughly a tenth) but that way of looking at it is based on the notion of traditionally very high levels of energy in use. Once you start to reduce the energy in use then the embodied energy starts to take on significance.
The energy associated with building sites has had very little study, especially for self build. It is probably mainly to do with transport costs, which can be relatively high, particularly in the countryside where delivery journeys for materials can be quite inefficient.
Upgrading existing property
This is a much bigger challenge than building from scratch but there are already a couple of examples in the UK of old houses being brought up to Passivhaus standard: Under the Sun in Birmingham and one in Lambeth, London. Work is more advanced on the continent, particularly in Germany. See this study
The Retrofit for the Future database gives details of dozens of mainly housing association and council properties which are in the process of being brought up to high insulation and air tightness standards. The PDFs go into considerable detail about the methods.