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Steel Designers' Manual - 6th Edition (2003)
Operational energy 283
Fig. 8.2 Comparison of operational energy requirements and resulting carbon emissions for
a typical air conditioned office and a good practice naturally ventilated open plan
office (source: Econ 19, Energy use in offices, Energy Efficiency Best Practice
Programme)
Although heating accounts for a significant part of the annual operational energy
use, it produces a relatively small proportion of the overall carbon emissions since
it is generally provided by burning natural gas. In the UK, gas produces only 41%
of the carbon dioxide emissions per kilowatt hour that are produced by electricity.
Therefore the greatest scope for reducing carbon emissions from commercial buildings
is in reducing the energy required for cooling, mechanical ventilation and artificial
lighting.
Energy use is heavily dependent upon building design, including such factors as
layout, orientation, thermal capacity, glazing arrangements, solar shading, cooling
and ventilation. The choice of structural system (steel or concrete frame 4 ) has been
found to have very little effect on operational energy requirements, so the following
notes apply in general to all commercial buildings.
Structural steel gives the design team the flexibility it needs to exploit these
factors to the full.
One of the major ways of providing the necessary comfort levels is to make use
of fabric energy storage. This involves using the floor plate to absorb heat during
the period when the building is occupied during the day and then purging it at night
as shown in Fig. 8.3.
Initially there was a perception that thick concrete floors were needed for the
system to be effective. However, it has been shown that, with a 24-hour cycle of
heating and cooling, the necessary volume and disposition of concrete can be provided
by composite construction. 2
Perforated permeable ceilings can be used to permit the necessary contact
between the warm air and the floor. Enhancements can be achieved by ducting air