The extent to which ‘greening’ the design of a building project increases the cost is a complex matter which depends on your priorities. It can be anything from a few percent to several hundred! Given that costs are a major issue for most people, it is important to have a strategy in mind so that the extra cash you have is spent in the most efficient way.
The PassivhausSee more on the Passivhaus standard. The PassivHaus Institute has pioneered a standard for low energy buildings. It includes very low energy usage and ways of achieving this. The word is derived from the idea of buildings which are fundamentally low energy and passive solar heated rather than using extra gadgets to heat them. See Passivhaus for the UK branch of the organisation. Institute reckon that Passivhauses are coming out between 4 and 6 per cent dearer than normal building prices once builders have had some experience in doing them but the learning curve can prove quite expensive.
The is an interesting breakdown of the construction costs of a Passivhaus on the Welsh Timber Forum web site.
Fortunately the things that make the most difference tend to be the cheaper ones (but not necessarily the easiest) to do. Increasing insulation causes a very small extra cost in materials but may involve non-standard construction details which many designers and builders are not well versed in, so it will take more time to find these people and learn the techniques. The same goes for making a building airtight. Very few builders have experience in the necessary techniques.
Regarding sustainable materials, often they will not be more expensive but it may take a lot more time to find them. A typical case is with timber where a few merchants will know about the Woodmark while most will not have heard of it or simply won’t care. The Woodmarked timber may even be cheaper, but it will take a lot more ringing round to find it.
There is a middle band of materials and building techniques which will definitely cost more but will probably be worth the extra. For instance, windows and doors with good insulation properties tend to come from manufacturers in mainland Europe and Scandinavia and cost more simply because they are better made. Ecological paints have been pioneered in Germany and tend to cost more here mainly because many brands are imported in small quantities.
At the high end for costs are the more exotic types of gadgets and newer technologies which are becoming available. Typically photo-voltaic solar panels are extremely expensive compared with the energy they generate. For a house to generate enough electricity to approach being carbon neutral might well cost tens of thousands of pounds. Before spending this sort of money it is important to make sure the cheaper but more effective things like high insulation levels have been covered.
CSH – A Cost Review
The CSH Code for Sustainable Homes. A standard for eco-houses developed by the Building Research Establishment. It covers a wide range of criteria Cost Review is a very detailed document published by Communities and Local Government which considers the extra cost implications concerned with building to the various levels of the Code for Sustainable Homes. It is mainly aimed at developers but has a huge amount of information that may be of use to the green self builder