The elements in a building are roughly divided into two parts
- the envelope of the building like walls floors, doors etc.
- the services such as wiring and drainage.
Thinking of a house as a number of elements is the traditional way of organising the construction process and works well around the various trades involved. However the challenges which arise with green building are often as much to do with the relationships between the elements as with the elements themselves. This is particularly true with thermal bridgingthis is a pathway where heat can easily escape (or get in) through some part of the structure. It is usually caused by some element of structure such as a steel lintel or wooden studwork. Also known as a thermal bridge. see more on thermal bridging and air tightness. The services also pose a challenge in terms of their efficiency, and take on a new dimension where energy harvesting and generation is concerned.
Until quite recently the building regulationsThese are the legal regulations which govern how a house is constructed. (not to be confused with Planning Permission which is about whether you are allowed to build the house at all or what it might look like) see Building Regulations), part LThe Building Regulations, part L is the section which covers energy conservation for new buildings (with part L1A covering new buildings and part L1B covering existing ones), have been mainly based on an ‘elemental’ calculation for heat loss. This was a fairly crude method of calculation of the U valuemeasurement of how much heat escapes (or gets in). The units are W/sq.m./°c. see Insulation properties of each element of the building and simply adding all the bits together to give a total heat loss. What is becoming a more important aspect now is the actual performance of the whole house when it is built. Hence the introduction of fan testing to find out if all the elements fit tightly together.
The other factor which becomes important is how the materials used in the various elements are sourced and eventually disposed of and how much energy goes into making them.
If you purchase a kit house you are very much in the hands of the supplier and you need to check out their materials and design whereas if you go down the route of designing and building it yourself then you have (hopefully) more control over all the ingredients.
The building site
There are two main challenges that arise once you actually get to the on-site work
- Reducing waste on site and recycling.
- Reducing transport associated with the building work
Reducing on-site waste is often harder than it first seems. Obviously a great deal can be achieved at the design stage by carefully working out the quantities of materials required and who can supply them in the correct batches at the right time.
Well organized storage is necessary especially where materials need to be kept dry so as to avoid damage due to waste.
Containers and packaging needs to be considered carefully because it is such a complex issue. Some items such as pallets are returnable, some such as cardboard boxes are probably recyclable while some plastics such as polystyrene may not be. Local recycling schemes are improving rapidly in many areas of the country so check out what they will and won’t take.
Transport associated with building sites can be enormous, especially when the work becomes more specialized. For instance the ‘shopping’ needed for plumbing or electrics can be a major part of the job especially for someone who doesn’t carry a large range of fittings etc. in the back of a van. Particularly if you are going to undertake this type of work yourself and especially if the building site is remote from a town with a good selection of merchants, the golden rule is to plan shopping trips carefully and phone beforehand to make sure they have it in stock. Also take the phone numbers of alternative suppliers so you can phone round as you go. This can avoid a lot of repeat journeys.