However, in humid climates re- radiation at night of energy received from the incoming solar radiation during the day, is difficult. Outgoing radiation to the sky at night proceeds most rapidly on clear nights, but with clouds overhead, and water vapour and pollution in the atmosphere, there is only an exchange between buildings and the surrounding atmo- sphere. Radiation towards the in- terior of buildings will be lower if the interior temperature is higher than the external temperature, but this is hardly desirable in a climate of small diurnal change. Geiger(17)
the
states that outgoing radiation will be strongest towards the zenith of the vault of the sky, because the thickness of the atmosphere, rela- tive to a radiating surface, will be
least in that direction. Directly to- wards the horizon the outgoing radia- tion will be weakest. Thus, if we wish to increase the heat loss by ra- diation at night, then we should de- sign our buildings with maximum area in plan. But this has the great disad- vantage of presenting a large roof sur- face to incoming solar radiation dur- ing the day.
in-
However, within a given plan area, increase in the perimeter wall length. although increasing costs, will crease the radiating surface area at night, and the area of contact with outside air for conductive heat loss. This is quite the opposite of the de- sign approach in colder climates. where the most compact plan shape and minimum wall area is desirable to reduce heat losses at night.
TABLE II
Natural air flow patterns around buildings $ Downwind Eddy Dimensions
Building Type
Roof Pitch
Width of Building
2A
4A
(End Elev.)
or Cross-Section
DDDD
པ་མམ་
Length of Building
*
8A 12A 16A 20A 24A
(downwind eddy dimensions †)
26
87
ཁ
A
33
51
71
8
81
2A
2
23
33
53
6
3A
21
31
41
51
53
64
51
A
81
113
153 161
174
18
A
63
11
161
183 183
203
203
220
ما
143
12/12
A
34
9
111
131
131
8/12
A
31
43
73
83
101
10
111
6/12
A
23
43
61
73
83
101
11
4/12
A
23
37
64
71
81
81
81
12/12
2A
23
54
91
113
131 141
15
8//12
2A
21
41
83
104
121
13
6/12
2A
3
4
63
81
10
124
142
13
4/12
2A
21
41
64
73 10
11
121
12/12
3A
3
6
103
101
15
167 179
8/12
3A
43
8
101
121
143
6/12
3A
42
6
83 114
121
13
4/12
ЗА
21
37
64
81
91
113
3/12
2A
3
54
81
101
11
13
141
2/12
2A
81
103
111
12}
1/12
2A
21
31 6 73
101
11
12
3/12
2A
21
41
61
81
11
112
133
2/12
2A
4
6
8
93
101
11
1/12
2A
23
4
3
53
81
81
9
22
22
222
* As a multiple of 'A', the building width.
2
151
121
† Measured at right angles to leeside, with each of the figures in the tables
expressed as a multiple of 'A', the building width.
$ From "Natural Air Flow around Buildings" by Ben H. Evans, Research Report
No. 59, March 1967, Texas Engineering Experiment Station.
Far East Architect & Builder March, 1967
Perhaps, in relation to the climate of Malaysia, some studies could be undertaken on similar lines to those presented by Olgyay(18) for Miami, in a Wet and Dry Tropical (Aw) Climate. Here it was found that the "optimal shape (of building plan) was 1:1.7, but up to 1:3.0 on the east- west axis is also acceptable”.
It is likely, however, that if studies were undertaken on the night re- radiation properties of building ma- terials in the humid tropics, then in designing for greater wall surface area and the new night-time criteria for thermal comfort, a different optimal building shape would result. But there are other factors to take into account, perhaps the most important for night comfort being cross-ventila- tion and sufficient air changes. Open space around buildings to encourage natural air flow will also allow the ra- diating surfaces to "see" the night sky.
Air Temperature Reduction
Mention of open space between buildings in the humid tropics draws attention to the need for a town plan in which the climatic aspects of town planning have been fully consider- ed(19) There have been many de- monstrations of the effects upon tem- perature, wind and humidity caused by incorrect planning(17, 18, 20-23), It should be possible to plan a city with- out worsening the climatic conditions.
In colder climates, town planning to prevent night-time lowering of the temperature of an area and to reduce wind effects is possible, while close and compact building is advocated in hot and arid climates to reduce the effects of incoming solar radiation during the daytime and to induce local microclimatic breezes. In warm and humid tropical climates, open planning is one way of making tem- perature reduction and increased air movement possible.
Temperature traverses, across cities, with instruments instailed on the side of a car, screened from the engine, have shown quite marked temperature differences between city and sur- rounding countryside in colder climates. of the order of 10°F or more under particular climatic condi- tions. Now even a corresponding 3 to 4°F temperature difference, in warm and humid tropical cities, would be quite significant and worthy of further study from the town plan- ning point of view, since such a tem- perature drop would assist in reduc- ing thermal discomfort, and it would also lower air conditioning costs.
a
As an example of applied climatic planning we may refer to Chandigarh, where Landsberg deduced that breeze extending from the ground to a height of 3 to 4 ft. would pass for two miles down the side of Capital hill. To take advantage of this natural phenomenon, medium class housing was situated at the foot of the slope.
Other useful conclusions were reached at Chandigarh. For example it was concluded that street layouts may be 20° out of the wind in either direction, and may deviate up to 30°
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