Memorandum by Max Fordham (TAB 29)
Targets for sustainability have been set by
the Royal Commission for Pollution. The targets are more strict
than the current Kyoto agreements and they need to be. The proportion
of the world population who have access to the benefits of industrialisation
must rise if the population of the world is to stabilise at about
10 billion people. We should not be encouraging a new building
type if it is inherently more inefficient in its carbon emissions
than other competing building types. Buildings where people work
need good light. Electric light is responsible for nearly half
the carbon emissions of an office building. As the thermal properties
of buildings are improved, using efficient glazing, CHP, etc,
The need to reduce reliance on electricity for lighting must also
be implemented. Natural lighting is the best use for solar energy.
The energy content of natural light is given by the relationship
100 lumens per watt. It takes between 30 watts and 3 watts of
carbon emission to produce 100 lumens of light. So natural light
is one of the most efficient ways of using solar energy to replace
carbon emissions. On an overcast day the sky produces 5,000 lumens
per square meter of which 2,000 lumens reaches a square meter
of vertical window. There is a limit to the depth into a building
which can be reached by light from a window. The limit is one
or two times the height to the window head. Tall buildings need
to be served by lifts, escape stairs, and other services. The
area of these essential, but not productive parts of the building
has to be minimised. For tall buildings the depth from the window
to the back of the office is maximised so that the ratio of useable
to total area is economically feasible. For the Nat West Tower
the useable to total ratio is less than 50 per cent and the depth
of the offices is around 7 metres. At Canary Wharf the depth is
around 14 metres, the building is more efficient in terms of net
to gross area, but he 14 metre deep offices rely on electric lighting.
Any modern building will have to show compliance with current
building regulations. The building regulations as currently tabled
are an interim stage in reaching the eventual targets for sustainability
and we should not be opening the doors to a building type, which
is bound to need electricity for lighting.
Tall buildings are exposed to strong wind forces.
It is generally accepted that the buildings need sealed envelopes
and mechanical ventilation and air conditioning. Mechanical ventilation
and air conditioning do increase the Carbon emissions of buildings.
Again we should not be encouraging buildings which will increase
The increase in town density should reduce carbon
emissions caused by transport. One of the important research results
of the 60s was that a density of around 500 p/ha could easily
be achieved by low-rise buildings. The current planning policy
of limiting housing density to 100 p/ha needs to be revised, but
it is not necessary to aim for say 5,000 p/ha as in Hong Kong,
nor is it necessary to build extravagant showy buildings now.
The requirements for phased means of escape
need to re-examined while we sort out what can be done (if anything)
to prevent collapse of buildings which may obtain more people
than can escape in a short time.
Max Fordham MA, FREng, FCIBSE, Hon FRIBA, Visiting
Professor Dept Civil Engineering & Architecture, University