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60
diation and indoor heat gains. In parts of the world where high solar radiation
intensity and continuously higher external temperatures are common, for exam-
ple Sydney with 35 °C d.b. and 24 °C w.b., the necessity for controlled air cir-
culation and refrigeration can be recognized.
Environmental temperature is a combination of mean radiant and air tem-
peratures. Intense solar radiation through glazing during the summer can lead to
the mean radiant temperature being higher than the air temperature. The tem-
perature of the air in an office, factory or residence may need to be kept to an
upper limit of, say, 26 °C d.b. in order to limit the environmental temperature
to 27 °C. Such conditions are tolerable, but not comfortable, for sedentary
work. Considerable discomfort is experienced when strenuous physical activity
is conducted.
The indoor air temperature fluctuates through each 24 h period owing to
the position of the sun relative to the building. South-facing rooms that have a
large area of glazing are likely to be exposed to the greatest indoor air tempera-
tures. The windows and doors remained closed throughout the weekend. The
office had only natural ventilation, no mechanical cooling, open light grey slat-
ted Venetian blinds, and had been used normally for the preceding week. The
exterior wall had a 70% glazed area.
The 24-hour clock time is 9 hours: that is, a time between 0 and 24 h. The
predicted outdoor air temperature curve has been calculated for maximum and
minimum values, of 28 °C d.b. and 13 °C d.b. on an hourly basis for 24 h. This
corresponds to the conditions after a week of warm sunny weather in June 1993
in Southampton.
This has been a common occurrence since 1990. A thermocouple tem-
perature logger, measured the outdoor air, indoor air and the internal surface
temperature of the outer pane of the double-glazed window, hourly. The ther-
mocouple that was adhering to the glass showed a combination of two factors:
first, that the air temperature in the cavity between the panes of double glazing
rose to 35 °C; second, that the glass absorbed some of the incident solar radia-
tion and was raised in temperature. The internal room air temperature was
measured in a shaded location at just above desk height. The room air tempera-
ture remained between 25 °C d.b. and 31 °C d.b. During normal use, the same
office produced an internal air temperature of 25 °C d.b. when the outdoor air
temperature peaked at 27°Cd.b.
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