Air pollution

Air pollutionOne fifth of humankind live in places (particularly cities) where the air is not fit to breathe. A cocktail of poisonous gases is given off by factories, power stations and aeroplanes, which combined with exhaust fumes from vehicles, causes respiratory diseases such as asthma. Air pollution from cities produces a cocktail of sulphur dioxide and nitrogen oxides, the byproduct of which is acid rain. Another byproduct is ground-level ozone, which has a highly corrosive effect on vegetation, leading to crop damage. Air pollution weakens trees’ resistance to disease, and makes them more prone to fungal disease.

Large urban areas create particular local climates which trap pollution, have less solar radiation and are warmer than the surrounding countryside by several degrees. In summer this can lead to uncomfortable and unhealthy conditions.

Planting can be used to improve the microclimate in a number of ways:

  • Use planting, water features and trees, and plant to increase cooling, shade and dust absorption. Select tree and shrub species which are tolerant of pollution.
  • Green roofs are another excellent way of modifying the microclimate. They insulate the building, retain water (which reduces storm-water runoff), cool the urban heat effect, and encourage wildlife. •
  • Growing foliage on walls can shield buildings from extreme temperatures and frost as well as sheltering the external envelope from rain.
  • Trees are particularly good as air and noise pollution filters, particularly near busy roads. Dust and pollutants adhere to dry twigs and leaves, removing 75% of dust particles.

Land contamination

Developing contaminated land affected by industrial processes and the use of toxic chemicals which are harmful to human health as well as other ecosystems is an increasingly important issue, as the current emphasis is on using brownfield sites within existing settlements in preference to previously undeveloped greenfield sites. The objective of a more sustainable form of development should be to deal with contamination in the most benign way possible.

Where contamination exists, it is often perceived as a barrier to redevelopment, and many people are unwilling to live on previously developed land. However, current planning policy means that brownfield sites will inevitably be recycled into new uses in order to protect greenfield sites. Cleaning up contaminated sites is an environmentally desirable consequence of this.

Very few sites are so badly damaged that they cannot be reused at all, but the type of contamination and the costs of clean-up will determine whether the site is suitable and financially viable for a house. When making a planning application for a site which might be contaminated, you will have to provide information on soil conditions and make proposals for dealing with any contamination present. Site decontamination is a very complex subject, and beyond the scope of this book: expert guidance should be sought.

You will have to balance the cost of the decontamination process against the environmental impact of the decontamination process itself. The most benign method involving least energy is biological decontamination using toxin-neutralizing plants such as willow saplings and reeds, but this takes time and requires careful preplanning and process management. Treatment with chemicals can be quicker, but uses a more energy-intensive product. Capping the contamination with clean soil, for example, does not get rid of the problem but may be cost-effective if contamination is not severe. The last resort is scraping the site clean and exporting the contamination, which may be essential for development, but is the least environmentally desirable, as it just transports the problem elsewhere and buries it. The economic viability of this method is also affected by the cost of disposing of contaminated soils in landfill sites.

Electromagnetic fields

This section examines the potential hazard of electromagnetic fields outside the home, caused by overhead power lines, electricity substations, large transformers and mobile phone masts. There is concern, but no conclusive evidence either way, that continued exposure to magnetic fields is harmful to human health and in particular is carcinogenic. There is no officially safe level set in Britain. Electromagnetic fields within the home are discussed in the chapter on the potential risks to health.

Whenever electricity is used, an electromagnetic field (EMF) is produced. There are two types of field produced: electric fields resulting from a voltage differential, and magnetic fields arising from a flow of current. Both diminish rapidly with increasing distance from the source. Electric fields can be screened by most common building materials, whereas magnetic fields will pass through most materials.

The principal sources of electro-magnetic fields are:

  • High-voltage transmission lines on pylons, which carry high current and therefore give off both high electric and high magnetic fields. Powerwatch, an independent pressure group, states that people living within 200 metres of overhead lines may be affected.
  • Low-power substations are found every few hundred metres apart in a typical urban area, and many existing housing developments contain substations. Again, minimize risk by siting housing away from substations or screening using thick concrete walling or similar which can screen electric fields.
  • There has been a public debate over the safety of mobile phone masts, and this will continue as the need for more masts grows with the proliferation of mobile phone use. The Stewart Report published in May 2000 gave the findings of an independent expert group set up by the UK government. It recommended that a precautionary approach be adopted when siting mobile phone masts, particularly in relation to schools and other sensitive sites. Generally, high masts (say 15 metres) are safer than lower lamppost type masts of 6.5 metres which may direct radiation straight into homes.

Costs and benefits

There are costs associated with dealing with noise, soil contamination and other site problems. Make sure that this is reflected in the valuation of the site. There is a cost in enhancing the ecology of the site, which should be reflected in the quality of the living environment you create.

Adaptability

Any system needs to be capable of adapting to changing circumstances for it to survive and be sustainable. Sustainable homes need to be designed so that they are capable of adapting, which they may do by being of a simple form that can be adapted to different uses; or they may be fitted with sophisticated service systems to cater for changing demands. This section looks at some of the implications of adaptable building.

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