‘This is a wonderful book that should be on the desk of every architect and planner. It shows how

‘Still air is important to achieve thermal comfort’
. Still air stratifies. If the 
temperature at floor level is cooler than at head level, people tend to get headaches.
Warm internal air temperatures near cold walls or windows that draw heat from the 
body also cause discomfort. Similarly, heat from a small source such as an electric fan 
heater is less comfortable than from a large warm wall. Fresh air and natural ventilation 
reduce these air temperature differentials.

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Boxes
Box 26 Contextual Design (the Case of Plastic)
Design must work into existing systems to change them. This is illustrated by the current 
debate over which is more ecologically sound: plant-based or fossil fuel-based plastics. The 
production of plastics involves fossil fuels as a raw material and energy source. Power plants 
and transport systems use more than 90 per cent of oil, and plastics use most of the remainder.
On the one hand, some scientists argue that plants should not be used as a raw material for 
plastics, but instead should be used as an energy source. Bio-engineered plant production is 
energy intensive. On the other hand, a firm currently producing plant-based plastics argues 
that as their technologies develop, energy efficiency will be greatly increased over time. After 
all, fossil fuel processes have had 200 years of development to improve efficiency.
1
Due to 
the changing geopolitical and biophysical context, corn-based recycling is already economically 
competitive.
2
Plastics can be grown in plants via a fermentation process or in the stalks and 
leaves of bioengineered crops:
•
Fermentation process: Typically, the plants are processed for sugar, which is then 
fermented. In this process, micro-organisms convert the sugar into lactic acid, which is 
then chemically transformed into plastic.
•
Bioengineering process: The fermentation process can be skipped by using bioengineered 
corn. The plants can be harvested for their corn and the stalks and leaves can then be 
harvested for plastic. In other words, this means two uses for the corn. 
Some advantages of plant-based plastics are that:
•
They are biodegradable and compostable (ie reduce landfill and cause less harm to 
animals); however, this process emits greenhouse gases.
•
Their production is far more energy-intensive than conventional petrochemical plastics, 
but uses far less fossil fuel as a raw material.
•
The price of oil is rising, making corn-based plastic economically competitive.
•
Burning the carbon in stalks does not increase net carbon dioxide in the atmosphere 
– assuming crops that absorb the same amount of carbon dioxide replace the plants.
•
They cannot easily be separated from bottles made from petroleum without expensive 
sorting equipment, which is out of reach of many small-scale recyclers.
•
They can contaminate the recycling of fossil fuel plastic if they get in the waste stream, 
and thus undermine the investment in recycling.
Some advantages of fossil fuel-based plastics are that:
•
Plastics grown in corn compete with other agricultural uses for land and water.
•
Plastics can sequester carbon if buried in landfill.
•
They are produced from fossil fuels as a raw material; however, far less fossil fuel (energy 
and emissions) is required in their production than plant-based plastics.
•
A lot of energy is required to grow corn.
The above simplified list of issues suggests apparent tradeoffs:
•
Relative value of agricultural land versus use of fossil fuel energy with emissions.
•
Relative value of fossil fuels as non-renewable raw material versus using fossil fuels in 
energy production, which produces greenhouse gases.
•
Economic and other values of established recycling industries versus avoiding the 
transport and machinery entailed in recycling.
•
Relative biodegradability versus carbon storage potential for fossil-based plastic.
In either case, the crops are generally grown using mineral fertilizer, which is produced in a 
very energy-intensive process which uses fossil fuels in the production of energy. If crops are 
fertilized with compost rather than nitrogen, the environmental impacts are greatly reduced.
3
The debates usually omit the design approach: to consider whether we really need the products 
and, if so, to consider whether there are better means of meeting the same needs.
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Positive Development