THESE two subjects are so inter-related and so dependent one upon the other that it is, difficult to disassociate them. Perfection in both substantially adds to the comfort of those attending the theatre. Fresh air is a prime necessity of life. Man can live for days without water, and for weeks without food, but without air he cannot live more than a few minutes. A constantly renewed supply of air at the right temperature is therefore essential. Considering that good ventilation is the first rule of hygiene it is astonishing that hardly a theatre in America is equipped with any scientific method of ventilation, good, bad or indifferent, although there are many excellent systems on the market. In the discussion of these two subjects the first to be treated will be heat. Heat is not a substance; it is a condition set up by an incessant movement among the restless tiny molecules that compose all matter. The demand for artificial heat depends largely upon climatic conditions and the habits of the people in the community. In Europe 59 degrees Fahrenheit is considered comfortable; in America the custom is to maintain about 70 degrees.

The general requirements of a heating and ventilating plant for a theatre are:

(I) Uniform distribution of heat, and the prevention of its waste by premature escape.

(2) A thorough diffusion of fresh air throughout the zone in which persons breathe, and a provision for avoiding perceptible currents of either warm or cold air.

(3) A prompt removal of all foul air.

Methods Of Heating

The methods of heating now in vogue may be divided into two general classes - direct and indirect radiation. The one that we shall consider is direct radiation. There are three means of producing heat by direct radiation: by hot air, steam or hot water. To produce heat by hot air requires a special furnace, which is difficult to regulate and is not sufficiently reliable for theatres. Heating by hot water, while it costs more to install, because of the increased number of fittings, is a trifle cheaper to operate, but it is not suitable for theatres because of the likelihood of its freezing in cold weather. Steam is therefore the only remaining system.

The following table of the relative cost of each method may aid in the process of elimination:

Hot Air

Steam

Hot Water

Relative initial cost of apparatus

9

13

15

Relative cost of operation for five years ................

29 3/4

29

27

Steam Heating

It would appear from this table that direct steam heating is the best system to meet all the heating requirements mentioned before. The principal advantage is its ability to heat uniformly, regardless of wind action. It is the cheapest and quickest and is also comparatively immune from freezing. Direct steam is broadly divided into two general classes, the gravity circulating system and the mechanical circulating system, the distinguishing characteristics being the manner in which the condensation water formed in the radiators is returned to the boiler. In the first type the condensate enters the boiler by gravity, and in the second type the condensate is returned to a receiver and is then forced into the boiler by a pump or return traps. Direct steam heating also lends itself to combination with other systems by means that will be considered later. The law usually requires that heater rooms shall not be located under the auditorium, stage, lobby or exits of the theatre.

Amount Of Heat Required

To install a heating apparatus it will first be necessary to ascertain the amount of heat required for a given building. To compute the number of feet of direct radiation required for a building, divide the cubic contents of the various rooms by the following factors:

Divide by

Dressing rooms, one side exposed..........

40 to 50

Dressing rooms, two sides exposed.....

30 to 40

Auditorium....................................................

60 to 100

Where there are windows, doors or other exposures employ the lower divisor above quoted.

The heat in an auditorium should be considerably lessened or turned off completely after the audience is stated, except where mechanical provision is made for introducing fresh heated air to replace the heated foul air constantly being expelled.

Longitudinal Section of Heating Diagram Indicating Ordinary System for Theatres.

Longitudinal Section of Heating Diagram Indicating Ordinary System for Theatres.

Steam Heating Plants

Steam heating plants are divided into three distinct parts; the boiler or steam generator, the radiators, and the supply and return pipes connecting the two. The best boiler is the tubular boiler. There are many varieties of this useful type of boiler, the horizontal and upright tubular boiler and the firebox type of tubular boiler. Horizontal tubular boilers are largely used for factories and power plants, and the upright tubular boiler lacks the capacity of the fire-box type, which requires no brick setting and is cheaper to install than other forms of tubular boilers. The cast-iron sectional boiler in common use also has not the capacity nor stability necessary for heating a large theatre.

For indications for setting a boiler, see the diagram on Page 145 showing the heating of a theatre. The following table, compiled by the Atlas Engineering Works, Indianapolis, Ind., may aid in the selection of the size of boiler required:

Proportions Of Horizontal Tubular Boilers

SHELL

THICKNESS

TUBES

Nom.

Rated

H.P.

Diam. Inc.

Length feet

Shell Inc.

Heads Inc.

Diam.

Length feet

Heat

Surf. sq. ft.

Grate

Surf sq. ft.

No.

Inc.

15

36

8

1/4

3/8

26

3

8

214

5.8

20

36

10

1/4

3/8

26

3

10

266

8.3

25

36

12

1/4

3/8

26

3

12

318

9.5

Nom.

Rated

H.P.

Diam. Inc.

Length Shell feet Inc.

Heads Inc.

Diam. No. Inc.

Length feet

Heat Surf. sq.ft.

Grate Surf sq. ft.

30

40

12

1/4

3/8

34

3

12

404

12

35

42

12

1/4

7-16

40

3

12

464

12.8

40

46

12

9-32

7-16

42

3

12

491

14.6

45

48

12

9-32

7-16

48

3

12

551

15.3

50

48

14

5-16

7-16

40

3 1/2

14

630

16.

55

52

14

5-16

1/2

44

3 1/2

14

693

16.7

60

54

14

5-16

1/2

46

3 1/2

14

721

18.

70

54

16

5-16

1/2

40

4

16

817

20.8

75

60

14

11-32

1/2

62

3 1/2

14

940

21.5

85

60

16

11-32

1/2

52

4

16

1045

22.2

100

66

16

3/8

1/2

64

4

16

1265

25.

125

72

16

7-16

1/2

82

4

16

1578

29.5

150

72

18

7-16

1/2

82

4

18

1775

36.5

The size and location of the boiler pit and other minor details should be left to the discretion of the heating contractor.