Various types of pollution will occur at the three stages of a building’s life. The degree of pollution at each stage can be minimised by good design.
During construction there will be five main sources of pollution (including indirect CO2Carbon dioxide is a gas which is given off when carbon based materials such as fossil fuels (coal, oil, and natural gas) are burned. It is called a greenhouse gas because it works like the glazing of a greenhouse and causes global warming pollution) caused by:
- The sourcing and manufacture of the building materials themselves (how much energy is used? Is it a clean process?)
- The transport of the materials to site (how much CO2 is released into the atmosphere?)
- The site work itself such as machinery, heating, material treatment, etc. (Is it a clean or a dirty site in terms of chemicals, particulates, solvents, etc?)
- The travel to site (is it heaving with vehicles that have travelled huge distances?)
- Disposal of damaged or excess building products
The first of these should be considered at the design stage (the others are more about site management).
There are now available several good sources of information on how ecologically sound the various methods of production of most building materials are.
The Inventory of Carbon and Energy gives a thorough listing of the embodied energythe total amount of energy it takes to make a material (or a building). See more on embodied energy of materials (which usually reflects how much pollution is caused in their manufacture).
It can be very tricky or impossible to establish how many air/land/sea miles are involved in the supply of building materials. A few may be relatively easy. For instance you might find a source of timber from local woodland or a roof tile supplier might source its clay locally. But when it comes to something like aluminium then the bauxite may have been mined at one end of the world and taken to the other for smelting before it gets to you. Increasingly, complex items such as central heating boilers or control equipment will have parts made all over the world and are often flown around before assembly. Common sense may help here but there will be no way of really finding out about this.
The building’s lifetime
The pollution created by a building during its lifetime will depend on many factors; mainly the energy it uses for heating, lighting and power for electric appliances and also the effluents the house produces in terms of waste (household waste and sewage).
There is also the indoor pollution it creates due to poor air quality and maybe electromagnetic pollution.
Design your house to the best energy standards you can afford. Preferably 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. standard or the AECBthe Sustainable Building Association gold standard. Failing that, rate as high as you can on the Code for Sustainable Homes. The same goes for alterations and improvements.
Flexible design acknowledges that the usage patterns of a house will tend to change over time and that regular alterations to buildings is a polluting activity. It tries to overcome this problem as much as possible with flexible design.
Also try to go for a design that will endure and be pleasing over the long term. In the US at present the heaviest energy use in terms of ongoing changes to housing is the constant renewal (every 7 years on average) of fitted carpets. These are usually man-made acrylic products and use a huge amount of oil energy in their production. In contrast a Scandinavian approach has tended to be more towards timber floors with mats of natural materials. This is just one example. Getting design right in the beginning will reduce pollution in the end.
In the “cradle to grave” way of looking at things (or Life Cycle Assessment) the effect of pollution during demolition needs considering. Ideally, new buildings should be designed so that when they are demolished all the materials can be recycled or even reused. It is also important that toxic materials are not present.
Examples of toxic materials that turn up during demolition are asbestos, CCA treated timber and plasterboard. Increasingly on the continent materials which include formaldehyde are considered pollutants (and banned from manufacture, e.g. chipboard is banned in the Netherlands). This usually occurs because the dumping in landfill sites results in underground chemical reactions which produce other toxic chemical bi-products which get into watercourses.
Re-usability of materials is quite a complex subject because although until recently, many building materials have been highly reusable, this is changing. Stone, bricks, wood, a lot of roofing materials, etc. get reused routinely with little pollution involved. Glass has been an exception because it is very difficult to re-cut old glass. Metals get recycled very efficiently (unlike plastics). It is now possible to mechanically clean the mortar off old bricks. Increasingly the question becomes whether cleaning up processes are more polluting than manufacturing new.
Most plastics used in building, particularly membranes are not being recycled at present. However things are changing rapidly. PVC is a case in point and the technology is now available to recycle it.
There is a huge potential for reusing PVC waste pipe and soil pipe and PVC guttering which are almost routinely skipped. Although these products would be better phased out in their new form (and be replaced with PEPolyethylene or just plain old polythene or metal) they can often be reused because they are mainly of standard diameters and are often in good condition and connectors are still available.
The reuse of push-fit plumbing is an interesting subject because it is so new. Mostly made of PEXCross linked polythene. A stronger form of polythene much used in water pipes polythene, the tube and connectors may well prove to have second or third lifetimes after demolition. This may depend on the surface condition of the tube, the migration of plasticisers, the ability to test old pipe and fittings and the availability of the correct O rings.