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Copyright © BEAM Society Limited. All rights reserved. Page 112
rooms served by a single thermostat. Temperature between rooms or
locations within a room may vary due to large window areas, or large
vertical surfaces (which may create convection currents resulting in
cold air at floor level), causing discomfort for some occupants. The
temperature level at which people feel comfortable will depend on
activity levels, clothing, age and natural body temperature which will
vary from individual to individual, and seasonal conditions.
Humidity influences thermal comfort by affecting the human body’s
ability to lose body heat through perspiration. In humid conditions it is
more difficult to lose heat, the effect is therefore the same as raising
the temperature and people feel “sticky”. High humidity also
encourages the growth of mildew and other fungi on building fabric
and furnishings. Furthermore in the humidity is too low it can cause
eyes, nose or throat to dry which may lead to discomfort, irritation and
increased susceptibility to infection. Extremely low humidity can cause
static electricity which is uncomfortable for occupants and can affect
the operation of computers.
A certain amount of air movement round the human body is essential
for thermal comfort. It is also important in dispersing air pollutants.
The required level of airflow depends on the air temperature and
humidity. In the hot and humid summer months, for example, greater
air movement can help produce a more comfortable environment.
Airflow is determined by ventilation and convection currents (created
by hot air rising and cool air falling) in a room. Blocked or unbalanced
ventilation systems, or too low pressure levels in ventilation ducts may
restrict air movement, producing a “stuffy” atmosphere which makes
occupants feel uncomfortable.
Airflow is also sensitive to changes in room occupancy; installation or
removal of partitions, walls, the size, quantity, arrangement of office
equipment and furniture, and building use. Too much air movement
results in draughts and excessive cold.