Fig. 93.

The cold air enters through windows at d, e, and f, the last named being for the radiators in the rear. It then enters the casings of the indirect stacks on their under side, passes up between the radiator surfaces, and flows into the several rooms through the hot-air flues j, which are built in the walls. All the foul-air ducts from the rooms on the first and second floor are led downwards to the basement, where they connect with the main flues g and h. On the third floor, however, they discharge directly into the chimney, as shown in Fig. 95. All the hot-air inlets are located about 6 inches below the ceiling, and the foul-air outlets are placed on the opposite side of the room, just above the baseboard. It will be noted that the warm-air registers are located in cold outer walls, while the foul-air ducts are run only in warm interior walls.

Fig. 94.

Fig. 95.

304. Figs. 96 and 97 show an ordinary two-story schoolhouse, of eight rooms, ventilated and heated by modern methods. The fresh cold air is taken down through a shaft a, which extends sufficiently far above the roof to insure its not being seriously interfered with by the wind. It is then driven by a centrifugal fan b, through a heater d, and is delivered to the vertical ducts h, by the pipe e; the foul-air vent is shown at v. A part of the air passes around the heater and is delivered cold to the wall ducts by the pipes c. The hot-air flues for the various rooms are made separate, and each one is provided at its foot with a mixing valve, so that the temperature of the air supplied to any room may be quickly changed without affecting any of the others, and without diminishing the volume of the air supply. Both the heating and ventilating flues are located in the inner corners of the rooms, the hot-air register being near the ceiling, and the foul-air outlet near the floor.

Fig. 96.

Fig. 97.

The basement rooms containing the water closets are supplied with air by means of the pipes f, the foul air being taken out by the flues g which run up alongside the smoke stack k.

All the other vent flues are run to the attic separately, and are there united into a single stack /. No cowl or other protection is needed over the top of this outlet, if provision is made at its base to drain off any rain that may fall into it.

No radiators are used at any point, except in the main corridor on the first floor, and two of these are arranged just below the level of the floor, to serve as foot warmers. All the other heating surface is concentrated in the heater, where it can operate with the greatest efficiency. The engine n is shown attached directly to the fan.

The attic floor is lined with thick paper and carefully made air-tight, both to prevent any waste of air, and also particularly to guard against the loss of heat from the rooms below.

305. The arrangement of hot-air registers here shown is suitable only for rooms of moderate size. In large rooms, the cooling effect of the outer walls is likely to be so great as to produce a considerable drop in the temperature, making the remoter parts of the room quite uncomfortable. In such cases, the registers must be increased in number, and the warm air must be delivered more directly to the cold part of the room.

Where this cannot be conveniently done, the deficiency in heat may be made up by running pipe coils along the outer walls, especially under the windows. Coils are better for this purpose than radiators, because the heating surface is distributed over a greater space. Each line of pipe should be provided with valves at both ends, so that any number of them may be shut off if desired; otherwise, they are liable at times to give off too much heat, and become a source of great discomfort to the students sitting near them. The clothes closets or "cloak rooms" should be separated from the class rooms, and should be thoroughly ventilated, independently of all other rooms. They should also be so arranged that they may at times be tightly closed for purposes of disinfection.

Fig. 98.

Fig. 99.

306. Figs. 98, 99, and 100 show a manufacturing establishment, two stories high, 50 feet wide, by 200 feet in length. The fresh-air supply is driven through a steam heater a, having 4,000 square feet of tube surface, by a fan b, which has a wheel 72 inches in diameter and 33 inches wide. The hot-air mains are carried up to the roof and are run along horizontally just above the tie-beams of the trusses. Vertical branches are carried downwards to the first and second stories at moderate intervals, and are provided with gates at their outlets.

This arrangement of piping prevents any interference with shafting and machinery, and the air being delivered at the top of the room, all stagnation or accumulation of foul air is prevented. The foul air is vented through ducts under the floor, which discharge through openings in the outer walls.

The fan takes air from the outside of the building during working hours, and from the inside at other times, when there are but few people in the building. The heating is done principally by the exhaust steam coming from the shop engines, live steam being used only during the night.

Fig. 100.