Imágenes de páginas
PDF
EPUB

room, which, in the evening, is lighted by 90 gas-burners. The capac ity of this room corresponds to 200 cubic feet to each person.

Ventilation in the two rooms during the day is limited to 350 cubic feet to each person, which necessitates the renewal of 140,000 cubic feet an hour in the second story and 70,000 cubic feet an hour in the third story.

The rooms are warmed by two heaters found by direct experiment to have a heating-capacity equal to 81 per cent. of the heat generated by the fuel,* and having proportions corresponding to 4 square feet of heating-surface for every 1,000 cubic feet of room-area, supposed to be ventilated by a complete change of air twice an hour.

The warm air is carried to each floor by three vertical flues leading into a large and long pipe extending throughout the whole length of the rooms, which receives fresh air from without in order to regulate the temperature of the air admitted into the room. This air enters horizontally near the ceiling.

The volume of warm air, at a temperature of from 140° to 150° ascending in the flues before being mixed with cold air, was found to be, in the second story, 106,000 cubic feet an hour; in the third story, 73,000 cubic feet an hour; and this has been found sufficient to maintain in the rooms a temperature of from 60° to 70°, when that of the exterior air was 350 or 40°.

According to the instructions given to the builder, the foul air should have been carried away from the second story by thirteen flues, the proportions of which had been determined by applying the rule adopted in § 51, which fixes 28 inches a second as the velocity which the foul air should have in the first series of ventilating-flues, as indicated in the following table:

[blocks in formation]
[blocks in formation]

71,000 cubic feet. 20 cubic feet. 9 square ft. 4 of 1 foot 5 inches x 1 foot-1.5
3 of 1 foot 1 inch x 1 foot-1.1 sq. ft

8q.

ft

6

3.3

9.3

* Annales du Conservatoire des arts et métiers, 6e vol., p. 325.

Note. The builder actually gave smaller sectional areas to the flues; still the intended results have been secured.

In the first series of collecting-flues in each story, where the velocity is to be 39 inches a second, the sectional area should be

For the second story, amount to be renewed in 1 second = 39 cubic feet, sectional area

For the third story, amount to be renewed in 1 second =20 cubic feet, sectional area

.....

Square feet.

12

6

In the two collecting-flues terminating at the bottom of the general ventilating-chimney, the required velocity being 4 feet a second, their total sectional area was fixed at

[blocks in formation]

The latter flues carry the foul air to the bottom of the chimney, which is 56 feet high, and has a sectional area of 11 square feet. The two smoke pipes being each 8 inches in diameter, or 2 feet in circumference, and having consequently 56x2=112 square feet of surface exposed to cooling, were not able, even in ordinary weather, to sustain the draught of the chimney, and a small auxiliary fire was deemed necessary. To this was given a surface of about 100 square inches, which, when burning 33 pounds of coal an hour, carried off, on an average, 140,000 cubic feet of air an hour in the second story, and 70,000 in the third story. If the dimensions of the ventilating-flues given to the builder had been followed instead of being reduced to 16 square feet in the second story and 8 in the third, it is evident that the amount of air carried off would greatly exceed the prescribed amount, which shows that the rules which have been given allow for even serious defects in construction.

The observations made in this building in regard to the results of warming and ventilation lead to this important conclusion, that with well-made heaters and a properly arranged system of ventilation, schoolrooms with 350 cubic feet of air to each pupil may be comfortably warmed and ventilated by the use of no more fuel than is required for the injurious heat obtained from the cast-iron stoves used in most schools.

ADULT-SCHOOLS.

63. Similar plans should be adopted for adult-schools; the only change to be made consists in increasing to 500 or 700 cubic feet the amount of air to be carried off every hour for each person; or, in other words, to increase the size of the foul and fresh air flues.

NIGHT-SCHOOLS OF DESIGN.

64. These present a peculiar difficulty in changing the air and moderating the temperature, in consequence of the large number of lights

or gas-burners which they contain, which often produce a degree of heat in excess of that necessary to warm the room.

The general rule, which requires that the foul air should be drawn off near the floor, cannot be exclusively followed without causing currents of air heated from 85° to 95° to fall upon the students. It is, then, necessary to carry away the hot gases, the products of combustion, through the ceiling. But at the same time it is necessary to admit the fresh air, which in that case must be cool, at a certain height as far as possible from the floor.

But if the same room should also be occupied during the day as a study or drawing-room, and if it were then ventilated according to the usual rule by drawing the foul air off near the floor, it would be well at night to maintain that ventilation in order to assist the circulation and the descent toward the floor of a part of the fresh air brought in, of which to make up for the heating-effect of the lights, there should be a much greater amount than during the day.

Observations made in a school of design in Paris attended every evening by 200 to 240 scholars, and lighted by 90 gas-jets, consuming together 320 to 350 cubic feet of gas an hour, led for this special case to the following rules:

1. During the day, regulate the amount of foul air drawn off at the floor-level to about 530 cubic feet for each adult scholar and admit the fresh air near the ceiling.

2. For night-sessions, make escape-openings in the ceiling, the clear area of which should be calculated at about 88 square inches for every 1,000 cubic feet capacity of the room.

If there is no loft above the room in which the ventilating-pipes can be carried, special pipes may be placed at convenient points, removed as far as possible from those at which the fresh air is introduced. These pipes should be supplied with convenient valves, in order that they may be closed during the day, and the amount of the hot gases removed at night regulated.

3. Place in the two opposite walls of the room, or at least in one of them, at the height of 10, 13 feet, or higher, if possible, as many freshair openings as convenient, each supplied with a regulator to direct the air horizontally near the ceiling, the dimensions of these openings being calculated so that the volume of air admitted may be increased to six or eight times the total cubical capacity of the room, with an entering velocity of but 2 or 3 feet a second.

By means of these arrangements, drawing-schools may be made comfortable at night, which at present are almost like furnaces, and in which it becomes necessary to open some of the windows even in winter, notwithstanding the discomfort which may be experienced in consequence by the scholars nearest to them.

In the drawing-school just mentioned, the total amount of air carried off every hour was:

[blocks in formation]

which corresponds to a total renewal almost eight times an hour.

By means of this active ventilation, the temperature in the room has been maintained till 10 o'clock at night at 67° to 70° at 5 feet above the floor, and at 75° on an average at the ceiling, while, before the introduction of the means of ventilation mentioned above, it was, respectively, at the same heights, 80° and 90°.

65. Plans to be adopted in schools already built.-It too often happens that no plan has been provided in schools, and especially in night-schools, to produce even a partial change of air or to regulate the temperature, so that a stay in them is as unhealthful as it is unpleasant. There is, then, as we have said, no resource but to open the windows, and this is both uncomfortable and injurious to the scholars seated near them. These defects may, however, be removed, at least in part, in most cases by adopting the arrangements described in § 64 in the case of a drawingschool.

In order to carry off the hot gases arising from the lights, and prevent them from affecting the scholars, ventilating-openings should be placed near the ceiling. A number of ventilating-flues should be cut, the size of which may be calculated by the preceding rules; if possible, making them so large that the air may be renewed four or five times an hour. If, however, it is only possible to make one flue, it should be connected by means of a horizontal pipe, with a series of orifices in one of the long sides of the room. At the bottom of this flue should be placed either a little grate or three or four gas-burners, each consuming about four cubic feet an hour, in order to keep up the draught when the external temperature is too high for natural ventilation to be effective. The use of gas is in most cases of this kind more convenient than a coal-fire.

On the side opposite to that by which the foul air is carried off, a number of ventilators should be put in place of the upper panes of the windows, and arranged so as to be opened more or less as needed, in order to admit the fresh air as near as possible to the ceiling. By increasing and suitably arranging these openings, the injurious effects from the entrance of cold air will be avoided.

Arrangements of this kind have been recently adopted in the school at Saint Martin's Market, kept by the Christian Brothers, where there are about 100 scholars in the drawing-room every evening, light being furnished by a great many gas-burners. Simple wooden pipes carried up to the roof, and the employment of a few gas-burners, prove suffi cient to carry off the foul air and gas, and indirectly to draw in fresh air

through the ventilators placed on the opposite side to that by which the foul air is removed.

These means are far from being perfect, but their employment in school-buildings already built is almost always easy and inexpensive.

LYCEUMS AND COLLEGES.

66. In these institutions, where it is of the greatest importance to secure the change and purity of the air so as to promote the physical development of the youth, it is well to provide for this renewal at the rate of 500 cubic feet of air an hour for every child under 12 or 14 years, and 900 cubic feet for every person 15 years old or older.

The class and study rooms having to be warmed and ventilated constantly during the day, and the sleeping-rooms during the night, it is best to make use of such forms of heating and ventilating apparatus as include all the rooms of the same building. Those employing hot water should always be preferred, notwithstanding their greater first cost, because that is largely compensated for by their regularity of operation, and also by their economy of fuel.

Cast-iron stoves, too often used in these establishments, are extremely injurious, not only because they heat too irregularly, and often to excess, but also because the iron, a porous metal, produces a noticeable and dangerous alteration of the air.

67. Application made at the Toulon Lyceum.-M. Laval, one of the most skillful of French architects, and one who has for several years past been specially occupied with questions relating to the healthfulness of habitations, has made a very happy application of the principles just mentioned in the new lyceum at Toulon, which he designed. Some details in regard to it will prove of interest, since they will serve both as an exemplification of the rules and as a model to be followed in similar circumstances.

Fig. 16.

In this establishment, there is a main court-yard, giving access to all the rooms, (Fig. 16.) This communicates right and left, by means of passages, with the halls, studies, and class-rooms of the first and second divisions. At the rear, in a separate building, are placed the natural-history collections and the physical apparatus. Behind this building is the hospital-court,

around which are, on the ground-floor, the dining-rooms and the kitchen, and, on the second floor, the infirmary with its bed-rooms.

The lyceum will accommodate 300 boarding-scholars, occupying during the day six study-rooms and at night ten bed-rooms. There are also twenty-two class-rooms, each intended for forty scholars on an average, which should be ventilated at the same time as the study-rooms. All

« AnteriorContinuar »