Steam Heating and Ventilation.
Chapter I.―Introductory.
The first really practical treatise on heating and ventilation seems to have been published in 1824 by Thomas Tredgold, and in that volume much space is given to the importance of securing adequate ventilation, and also to the merits of heating by systems of steam pipes. Mr. Tredgold gives accounts of several buildings which were successfully heated in this way. It is cited that the first factory in which steam was used for heating was a cotton mill belonging to a Mr. Neil Snodgrass, in which a steam heating system was installed in 1799. This was doubtless about the first instance of the employment of steam primarily and systematically for the purpose of heating. Mr. Tredgold describes a factory which was equipped with a steam-heating system in 1817 as a substitute for stoves, which had been previously used. The building was 90 feet by 30 feet, exposed on all sides, and four floors high. Each floor was warmed by a single pipe running the length of the building at the ceiling and midway between the sides. The system carried 30 pounds steam pressure, but besides embodying the most inefficient location for the radiating surface, the system, as described, did not have over 450 square feet of heating surface for a building containing 91,800 cubic feet of space. Mr. Tredgold states that the system showed great improvement, both in economy and results, over the previous method, adding that the employees suffered much less from "chaps and chills," so that one can only imagine the wretched condition of factory employees in cold weather previous to that time, even in the comparatively mild climate of England.
The problem of artificial ventilation antedates that of steam heating by more than half a century, though, of course, it does not antedate the heating of buildings by various methods more primitive. Mr. W. F. Butler, in a handbook on ventilation, published some years ago, states that the first scientific consideration of the subject of artificial ventilation occurred in 1723, when a certain Dr. Desaguliers was commissioned to institute some means for making the atmosphere in the House of Commons more habitable; and the doctor seems to have installed a system which proved satisfactory, although it had been previously attempted by no less a personage than the celebrated architect, Sir Christopher Wren. Since that time the question of ventilation has occupied increasing attention in the minds of physicians, architects and other scientific men interested in the public welfare, but even to this day what may be called "artificial" or forced ventilation remains to a large extent a luxury.
From the earliest times in the latitudes of northern Europe and North America, some form of heating in cold weather has been a necessity for all buildings, whether caves or palaces, but even as late as the latter part of the nineteenth century such a thing as a uniform temperature in heated rooms in severe weather was never expected, while ventilation was invariably secured only by such means as would be accomplished by the circulation of air through doors and other openings. In the days of our forefathers, when houses were built with large rooms and great, high-ceiling halls, and when people spent a large part of their time in the open, air, there was in reality but little need of artificial ventilation; and in the rude homes of the poorer classes that which was secured through poorly constructed walls and through loose windows of oiled paper was generally much more than was desired. With the improvement of transportation facilities, however, and the gathering of large numbers of people into small areas, and comparatively large numbers in single buildings, the need of artificial ventilation, in order to secure anything like a wholesome atmosphere,gradually became apparent, and it is natural that the demand for such ventilation should be recognized first in a building like the House of Commons.
Out of the same economic conditions arose the necessity of heating buildings by steam. Buildings of all kinds had from the earliest days been heated by open fireplaces, in which logs, and later coal, were burned in considerable quantities, while the larger proportion of the heat escaped up the flue. But forests were in time reduced, cities grew, and buildings were made larger and with a much larger number of rooms; and people were forced to find more economical ways of heating than by laboriously carrying expensive fuel to separate fires in each individual room. Stoves were built to get more uniform combustion and save some of the heat lost up the flue, and gradually various forms of distributing heat through many rooms from one central fire were developed to economize labor. Heated air, heated water and steam were all in turn experimented with as a means of distributing heat, and systems employing them have been rapidly and scientifically evolved to meet various requirements, and are to this day very widely used. But since the time of Tredgold, heating by steam has increased in extent and popularity year after year, especially since the increase in size of buildings began to be very rapid, and its economy of operation and incidental advantages of convenience and simplicity have become more and more apparent, until at the present day, in some form or another, it is used almost universally in all installations requiring distribution of heat over any considerable area. In this country it is well within the memory of most men in active life when even our largest factories and office buildings were heated by means of open fires and stoves, but the development from a primitive life to a congested and complex civilization has been phenomenally rapid, especially in the last quarter century, and the greatest advances in steam heating, as well as in most practical sciences, have been made in that period. These have chiefly been due to the almost universal application of steam power and the tremendous economy effected by the use of exhaust steam for heating.
The problem of mechanical ventilation, therefore, though growing out of much the same economic conditions, was solved, to a large extent, independently of the question of heating; and with the development of heat distribution by steam much was lost in the way of ventilation. The old-time fireplace and stove insured a certain amount of ventilation, to say nothing of the mental exhilaration of the former, but heating by steam was accomplished with no ventilation whatsoever. Hygienically, therefore, it was a step in the wrong direction, but economically the lack of ventilation made it more advantageous, as ventilation requires the heating of all incoming air. Heat in cold weather was the prime essential, and it was always possible to obtain some amount of ventilation by what might be called the "natural circulation" of air through doors and windows. The fallacy of resorting to such methods exclusively has been pointed out in many tracts and treatises published since the latter part of the eighteenth century, but the fact remains that even to the present day a vast majority of our buildings, a large proportion even of our factories, churches and schoolhouses, and most of our fine office buildings, with their boasted modern improvements, have no mechanical means for insuring an adequate ventilation.
At the present day we have arrived at a considerable degree of advancement, however, and buildings might now be divided into two quite distinct classes those which are "densely peopled" and those which are "sparsely peopled" and our advancement is such that mechanical ventilation is generally looked upon as a necessity for all buildings of the former class, which may include schoolhouses, churches, hospitals, theaters, and other audience halls. In buildings of the second class, such as residences, office buildings and hotels, we have been, as a rule, satisfied with sufficient heat, and have relied upon such ventilation as is secured by the natural circulation methods. In such buildings, therefore, the system of heating most used is that known as "direct radiation," in which radiators, or some form of radiating surface, are located in each room, and connected by an arrangement of piping to a central source of steam or hot-water supply. The rooms are heated by radiation from the hot surface and by contact of the air with it, but no provision is made for the supply of fresh air.
Several adaptations of the ordinary direct-radiation system of steam heating have been developed, however, with a view of obtaining the advantage of ventilation which was secured in the old-time stoves and fireplaces. The principal one of these is what is known as the system of "indirect radiation," in which the radiators, instead of being located in the rooms to be heated, are all placed below them, generally in the basement of the building, and are enclosed in boxes, which are provided with air inlets from the outside of the building, and with flues running to the room to be heated. Fresh air coming through the inlet in contact with the radiator is heated and rises through the vertical flue by the natural upward tendency of hot air. Both heat and ventilation are in this way provided to the rooms by the incoming hot air. This system has been much used in residences, and also to a small extent in some buildings of the "densely-peopled" class, such as hospitals and hotels. But the system has a decided disadvantage, due to the fact that the amount of ventilation secured is practically proportional to the amount of heat required, and in warm weather but little, if any, ventilation is obtained. Furthermore, experience shows that in order to ensure reliability it is necessary to have a separate flue for almost every room and to locate the radiators, directly beneath the vertical flue, so that in buildings of any size, especially those more than one or two stories in height, the arrangement of radiators in the basement becomes difficult, and the system of air flues, which are necessarily large, is complex and expensive in space and also in construction.
In order to avoid the difficulties of the system of "indirect radiation" and yet secure some ventilation, a combination has been developed which goes under the significant title of "direct-indirect radiation." In this the radiators are located in each separate room, but they are of special construction, and provided with air connections through the walls of the building so arranged that a certain amount of air can be admitted through this connection so as to pass around the radiator, becoming heated by contact with it. The room is therefore heated both by direct radiation and by the incoming current of fresh hot air, and considerable ventilation is secured.
In this system, as in the "indirect," ventilation in warm weather is dependent on open windows and doors, and it has been as yet but little used. It has, however, in a few cases been adapted to office buildings and hotels, and in the opinion of the writer we may look for a very decided development of the "direct-indirect" during the immediate future in buildings of the more sparsely-peopled character, where the amount of ventilation required per square foot of floor area is comparatively small. But for such buildings this system only achieves its best results when combined with a mechanical system for exhausting the air.
As already mentioned, we have, perhaps, arrived to-day at a point in the advancement of hygienic science where some system of artificial or mechanical ventilation is looked upon as necessary for all buildings of what the author has called the densely-peopled class. It is difficult to define the limits of such buildings, as the height and nature of the room and length of time occupied affect the question, but in a general way any room or apartment in which each individual occupies less than 40 square feet of floor area should be included in such a classification, especially if occupied more than two or three hours at a time. The systems which may be employed for mechanical ventilation are numerous and varied, but they all embody the use of fans of one kind or another for forcing the air into the rooms, or exhausting it, or both, with proper provision for heating the incoming air in cold weather, and some one of the three heating systems is frequently, if not generally, employed in connection with a system of mechanical ventilation.