Hong Kong Builder
17
NATURAL AIR-CONDITIONING
Scientific Method of Planning House Openings, Insuring Maximum Comfort
Up to the time when the new theory of the so-called "Planned Sunshine" came into prominence in modern architecture, the architect, when called upon the task of designing a new house, concentrated upon one task only how to achieve the best possible combination of comfort of appointments with beauty in outward appear- ance of a building. Now an ambitious architect, who is desirous of keeping step with the exigencies of modern architectural design also takes into account the position of the sun in a given latitude in order to insure the maximum access of sunlight in winter and its minimum in summer. In other words, the aim of every modern architect is not only to design the house in conformity with the rules of convenience and neatness in appearance, but to make the utmost of the sun- planning technique which provides maximum coolness in summer and maximum warmth in winter.
Astronomical Basis
It is common knowledge that the earth: (1) rotates round its own axis and (2) revolves round the sun. In result of its former movement we have day and night; the latter causes the change of seasons.
Sketch No. 1 shows the observer standing in the centre of a sphere of an indefinite radius. Arrows indicate the direction of sunrays during the day. In 24 hours a sunray makes a full circumference due to the earth's rotation on its axis. Various phases of this circumference are also shown in this sketch. On Decem- ber 22nd the observer sees the sun passing 23° south- ward from the point where he is standing and on June 22nd 231⁄2 northward from the same point. In course of a year the sun path moves within these two limits because the earth revolves round the sun and the diameter of the earth has an inclination to the sun ecliptic of
SOUTH
HORIZON
PATH
OF
SUN 22 DEC.
No
PATH
wins
AT EQUINOXES
SUN
22
JUNE
WEST #
DOBSERVER
PATH
1
NORTH
"Cool in Summer, Warm in Winter" is the motto of modern American architects, by whose experiments in the field of sun-planning technique we may greatly benefit. An interesting test conducted in New York has shown that the effective sun heat on a wall facing west-north-west is six times as great in summer as in winter, but on a wall facing south-west it is almost five times as great in winter as in summer. Another experi-
ment proved that in a house built for experimental pur- poses in the latitude of New York with the main openings facing 25° south-west, the effective sun heat in winter was 4 times more than in summer. The same house built so that its main openings were directed to north- west, received 9 times less effective sun heat in winter than in summer.
23%. The maximum altitude of the sun (90°) at the equator is in March, the minimum in December (on the 22nd)—661⁄2° above the horizon, and on the 22nd of June, but on the northern side. On the equator the day is approximately equal to the night. It is thus possible to work out all the phases of the sun altitude during the year for any latitude.
Diagram No. 2 shows that on the North Pole the maximum altitude of the sun on June 22nd is 231⁄2° above the horizon and the minimum, 23% below the horizon. The day lasts there 6 entire months, and so does the night.
In the localities of average latitudes (45°) the maximum altitude of the sun is 681⁄2° and the minimum -212°.