No_4_August_and_September__1939 — Page 14

W

18

+66 ±

43.

+212

THE

229 DEC. 229 JUNE

NORTH POLE

-237-251"

45.

N

LATITUDE

TROPIe OF CANCER

EQUATOR.

TROPIC

OF

CAPRICORN

45.

S

LATITUDE

zat"

231.

SOUTH

POLE

N° 2

Hong Kong Builder

+43

In Hongkong, located within the tropics (22°) and slightly southward from the tropic of Cancer, the maxi- mum altitude of the sun on June 22nd is about 90° and the minimum on December 22nd is 43° above the line of the horizon.

Position of Openings

This excursion into astronomy is important from the point of view of enabling us to establish the most advantageous position of openings in the house consider- ing the position of the sun at various seasons in a given latitude.

If a house was to be erected in a polar latitude, all its windows must naturally face south, but the need of providing some darkness at certain periods of the "day" lasting six months, when its inhabitants have to sleep, must be taken into consideration,

The situation is different in mean latitudes, Middle Europe or South England, for instance. The providing

of sufficient shadow in summer is as important there as securing the access of ample sunshine in winter. It has been theoretically worked out and confirmed by experi- ments that the best position for openings in mean latitudes is approximately 25° southwestward.

Diagram No. 3 shows the line of horizon in the latitude of Hongkong and the extreme paths of the sun on December 22nd and June 22nd. The observer stand- ing in the centre on June 22nd will see the sun rise on the northeastern side of the horizon. At noon it will reach its maximum and then set on the northwestern side of the horizon. On December 22nd the sun will rise in the south-east and set on the south-west.

It is clear from the same diagram that from the astronomical point of view the most advantageous position of openings in Hongkong is opproximately 45° to the south-west. A house built in such a way that its main openings will be facing this direction, will get the utmost of "natural air-conditioning" in this latitude, namely, will be provided with maximum shadow inside the house in summer and maximum sunshine in the afternoons in winter.

As in Hongkong the problem of insuring maximum coolness in summer is of primary consideration, wide porches, shielding the walls from the sun's rays may help protect the houses from the excessive heat in summer

(Diagram No. 4).

✔

MORIZON

PATH

E

1

1

N° 3

SUN RAY ON 21 DE<

JUNE.....

N°

4

༠་

Z

However, one more important point is not to be neglected; when planning house openings in conformity with all the demands of the sun-controlling technique, the direction of prevailing winds in a given locality is to be given due consideration.

Winds

The ideal orientation is, naturally, such, when the architect is able to coordinate and harmonize the positions of the sun and the direction of the prevailing winds. Diagram No. 5 shows the winds predominant in Hong- kong. From October to March the predominant winds are from the north-east; in April and May, monsoons, blowing from north-east to south-west are most common, and during the hottest months of the year south-western and south-eastern winds prevail.