Green Architecture spirit-
environmental classification systems can often be
conceived within a closed loop which accepts current levels of consumption of synthetic materials.
Economic growth requires more and more buildings and raw materials but this can be challenged by the
development of interest in the use of natural materials that are fully renewable with only limited amounts of
manufacturing and processing. A good example of such a natural material is Hemp.23 Hemp is a fibrous
material which can be grown in the fields with a minimal amount of fertiliser and no need for pesticides. It
grows very quickly to enormous heights and the resulting crop can be used in many ways. Oil can be
extracted which has a variety of therapeutic uses, even ice cream can be made from hemp. The fibre can be
spun into material for high quality clothes and at one time was the principle material for rope making. The
left over hurds or straw can be used in building construction and fibres combined with cement or lime. Such
a 
natural material is infinitely renewable and has no known toxic or polluting effect on the environment.
There is no waste and the energy consumed in planting and harvesting is minimal. If we could makebuildings using such materials we can significantly reduce the use of synthetic materials such as cement and
plastics and metals.
Of course the ubiquitous renewable material is timber, but it takes a long time to grow and thus requires
careful management. Hemp and other forms of straw and reeds grow much more quickly. Bamboo is
another material which has similar properties and uses to timber but regenerates and grows much more
quickly. Innovative buildings from bamboo have been developed in various parts of the world.24 It is also
possible to use earth as a building material, but unlike fired bricks or tiles, which require a lot of energy and
processing, earth can be used as it is dug up on site. We can thus imagine the possibility of creating
buildings which are largely composed of materials which are both natural in origin, locally sourced and
resulting in zero or nearly zero emissions. While the use of such materials may seem impractical at present,
the idea has to be seen as a challenge to anyone interested in green building.25
How can we argue that a building is green and environmentally friendly when it is still composed of
materials which have required a lot of energy, processing, waste disposal and transportation to get it into
place? Thus in the future we are likely to see far more discussion of the use of zero emission and natural
materials or at least their incorporation into more conventional buildings. The use of such materials,
particularly hemp and lime, bamboo and earth construction are likely to be subjects for future issues of the
Green Building Digest. Strawbale construction is dealt with in this book and is the best known example of
using a zero emission, fully renewable, virtually waste product as a replacement for materials such as
concrete blocks, giving very high levels of insulation.
What is Straw?
It is a natural raw material, the by-product of the harvesting of wheat, rice, barley, oats and rye. Straw also
comes from maize, millet, sorghum and hemp and other forms of crop such as sugar. Over 750 million
tonnes of straw are produced worldwide annually. About 60% of straw is baled with the rest ploughed in.
Of 17,000,000 hectares of farmland, 3,353,108 are devoted to cereal crops in the UK with nearly 2 million
devoted to wheat (1996). Between 2.75 and 3.5 tonnes of straw are produced per hectare, suggesting 10
million tonnes of straw are produced in the UK annually.6
At one stage straw came to be regarded as little more than an embarrassing companion to the grain crop.7
However straw is not necessarily a waste material. In organic farming straw is very important and it is the
emphasis on petrochemicals and artificial fertilisers that have reduced the need for straw. One authority
argues that the energy contained in straw is twice as great as the farm’s fossil fuel consumption,8 so it is
clearly important to make good use of this embodied energy. Straw has many uses; as a fuel for heating, for
paper and packaging, as a food, though it needs a lot of treatment for this. It was used in straw boards
(Stramit) and traditional mixed with earth for cob and pise construction.9
It is not right, therefore to call straw a waste material and as there are moves towards more organic
farming it will be used more as animal litter and thus as part of compost making. It can be ploughed back
into the soil. A great deal of straw is also used in mushroom farming. However the use of straw bales for
building in the short term is not likely to make a big dent in the supply.
Different kinds of straw?
Most forms of crop straw are suitable for building when baled. There are different strengths of stem, with
wheat possibly being stronger, but there can be great variations depending on weather, soil, levels of
fertiliser, growing time etc. As standards of straw bale building are established, such issues may become
important, but, the density and moisture content of the bales is more important than the type of straw used.
However not all straw is necessarily suitable, for instance there has been some experimentation with the use
ofHemp straw, but anecdotal evidence suggests that hemp is very tough and difficult to use with bale wall
techniques.10
Normally two string straw bales cost around £1–£2, but larger three string bales cost more. The large
round bales which are increasingly seen are of no use, but straw bale enthusiasts might consider acquiring,
borrowing or hiring a baling machine and re-baling straw obtained from whatever source. Often bales which
are normally produced by farmers in the field are not ideal for construction as they are too loosely baled. It is essential that straw is used for construction and not hay. Hay bales are made from plant material that
is green/ alive and not suitable for this application.11 However there are apparently buildings made of hay
bales in the USA and many people confuse the two referring to hay when they mean straw.
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