Hong Kong's climate-
its implications on design
Design for Climate — II
ONE of the qualities which dis- tinguishes man from most animals is his ability to adapt to living in all climatic regions of the earth, even though the range of environmental temperature to which his body can be adjusted is very small. (The range is governed by the extent that the deep tissue temperature can be maintained within the thermal comfort zone' by vasomotor control).
Man makes the adaptation by ap- plying his intelligence and technical skill to provide himself with shelter, suitable clothing and warmth.
It was indicated in the previous paper (Far East Builder, January 1968)2 that the environmental shelter is itself affected by various factors, climate being one of the natural phy- sical influences. This, together with the other constituents of the built environ- ment, viz. the visual, thermal, spatial and acoustical constituents, affect the comfort and general well-being of the occupants.
A prime objective of architecture is "to serve man and his living comfort. Man's comfort is thus the measure of the extent to which his physical en- vironment should be controlled.”
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For the architect, a main problem in the creation or production of a balanced environment is to ensure that it does not place undue stress on the body's heat-balance mechanism in terms of thermal comfort. How then does Hong Kong's climate affect the fundamental approach to environmen- tal design?
The term climate, in the context of this paper, is used to denote general- ly the physical environment under which man lives and works, encompass- ing the weather in terms of the time- mean values of the major meteorologi- cal elements pressure, radiation, temperature, humidity, rainfall and wind.“
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The need for classifying climates in relation to building design has been expressed, with the inference that buildings should be designed according to the different climatic regions." The problem of environmental design
1. An understanding of the climatic elements and their effects on thermal comfort conditions in buildings;
2. Presentation and application of outdoor climatic data in terms of de- sign values;
by K. H. Tang
with reference to climate therefore in- heat is transferred from a warm ob- volves the following aspects:
ject (usually the body) to the cooler one in contact with it (usually the air); radiation exchange, particularly in the long infra-red, controls the amount of radiant heat exchange between the body and the surrounding surfaces; re- lative humidity affects the rate of eva- poration from the skin and hence the amount of evaporative cooling; while air movement enhances evaporation and causes a cooling sensation without necessarily reducing the actual tem- peature. Table 17 summarises the en- tire process involved in the thermal balance of the body.
3. A knowledge of the thermal performance of building materials and structures as they affect indoor thermal comfort conditions.
Thermal comfort
Basically, human thermal comfort depends on the ability of the body to maintain a thermal equilibrium with the surroundings through the process the surroundings through the process of heat exchange by convection to the air, by radiation to the surrounding surfaces and by evaporation of mois- ture from the skin and the respiratory tract. Hence, thermal comfort depends on the combined effect of the four meteorological elements of tempera- ture, radiation, humidity and wind (air movement).
A change in any one of these fac tors will disturb the heat-balance mechanism of the body, which will automatically react and adjust to the new situation.
Air temperature affects directly the process of heat conduction in which
GAINS
1. Heat produced by: a) Basal processes b) Activity
c) Digestive processes, etc.
According to Herrington, the ther- mal environment is "home plate" as far as the physical world of energy and thermal adaptation to life and being are concerned. Any deviation from the thermal comfort range will lead to bodily discomfort, even sickness and possibly death. If sunstroke or heat- stroke is considered the upper tempera- ture limit for man's existence and free- zing point as the lower limit, man will intuitively seek a comfort condition which is about half way between what he can tolerate in a cold sense with- out being grossly uncomfortable, and the point which would require real ef- fort on the part of his circulatory sys- tems and his sweat secretion system in
Table 1
LOSSES
d) Muscle tensing and shivering in
response to cold
2. Absorption of radiant energy:
a) From sun directly or reflected b) From glowing radiators
c) From non-glowing hot objects 3. Heat conduction toward the body:
a) From air above skin temperature b) By contact with hotter objects 4. Condensation of atmospheric mois-
ture (occasional)
5. Outward radiation:
a) To "sky"
b) To colder surroundings
6. Heat conduction away from body:
a) To air below skin temperature (hastened by air movement-con- vection)
b) By contact with colder objects 7. Evaporation:
a) From respiratory tract b) From skin
Far East BUILDER, November 1968.
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