A text-book on hygiene and pediatrics from a chiropractic standpoint

HEATING

GENERAL CONSIDERATIONS

Heat from Hygienic Standpoint

The subjects of heating, lighting and ventilating will be treated purely from a hygienic standpoint and in no sense from the standpoint of engineering. The proper manner of heating a building is not within the scope of hygiene, but becomes a question of proper engineering and a subject to be considered from that angle. We are concerned only as the heating of buildings influences the health of the occupants.

Combustion

In parts of the country where the temperature goes below 60° F. it becomes necessary to provide artificial heat to warm houses in order that health may be maintained at the least possible expenditure of energy. The most common method of producing heat for heating purposes is by combustion. Its obedience to certain physical laws is infallible. Heat is liberated from such material as coal and wood by combustion and is the result of the chemical action of this combustion; it is then transmitted to the rooms to be heated either by air, water, or steam unless the combustion takes place in the room to be heated; then it is distributed throughout the room by radiation from the open fire or conduction from above.

Molecular Theory

Up until the beginning of the nineteenth century heat was believed to be a substance that had no weight and the name caloric was given this hypothetical substance. Davy and Rumford, through a series of experiments, proved that heat is a violent agitation of the molecules of matter. From this we have the molecular theory that as the velocity of the molecules is increased heat is produced and the temperature raised. The words heat and temperature are not interchangeable. Heat is the cause and temperature is the effect. Temperature indicates the presence of heat and the degree of temperature represents the intensity of the heat, but not the quantity. Heat in the same amount may be imparted to two bodies of the same substances, but different mass, and one will be hotter than the other; therefore, the specific heats of the two substances are different. To illustrate: Place in the sun a receptacle containing two gallons of water and one containing one gallon of water, both the same temperature. Leave them for a given length of time and they will become warm, but the one gallon will be warmer than the two, because of the difference in the amount of water to be warmed. The same amount of heat was applied to each, but this did not produce the same temperature in both. Again the same quantity of different substances may be exposed to the same heat, but the temperature will not necessarily be the same, for some substances heat more rapidly than others. It requires more heat to raise the temperature of water to a given degree than it does the same weight of any other substance, except hydrogen. This is the reason water gives off more heat than any other substance that cools through the same number of degrees.

Normal heat is produced in the body by the expression of calorific mental impulses and by the oxidation which is carried on in the tissue cells. The amount of heat produced in the body is adaptative to the needs of the body and is under the direct control of Innate Intelligence.

Air is carried into the lungs in respiration and by the action of Innate the oxygen is absorbed in the air cells and passes into the blood. It is carried in the blood by the hemoglobin to the tissue cells where it comes in contact with the calorific mental impulses and combustion takes place.

Body Heat

The normal bodily temperature is 98.6° F. Variation above or below this point indicates abnormality. This heat can not be supplied artificially from without. It must be generated within the body. It therefore becomes obvious that the temperature outside of the body is not regulated for the purpose of supplying the body with heat. The temperature of the atmosphere must, however, be regulated in order that there may not be an abnormal loss of the bodily heat. The bodily heat is being constantly lost to the outside air as follows: 30% by contact with the air, about 43% by radiation and about 27% by exhalation and other losses. We may sit in a room that is warm enough, say 75° F., and yet if we are near a cold wall we will feel chilly. We say we feel the cold coming from the wall, while in reality we feel chilly and cold because the body is losing its heat abnormally to the cold wall by radiation through the air.

When the air is comparatively dry the equality of the bodily heat is maintained by a steady but imperceptible evaporation from the skin. In moist air this evaporation does not take place so readily since the air is already laden with moisture, so instead of the moisture being absorbed by the air it forms on the surface of the body as perspiration. This is why one perspires more in a moist air than in an atmosphere having a low humidity. When the air is kept in constant motion there is an increase both in the evaporation from the surface of the body and also in the heat conduction by the constant supply of fresh air to take the place of the moisture-laden and heated air around the body.

The normal heat given off from the body raises the temperature of the air surrounding the body and tends to create upward currents. This is Nature’s method in freeing the body from the envelope of vitiated air which surrounds it as a result of the natural processes carried on through it. Therefore, if the temperature of the room is too nearly the same as that of the body it will be necessary to make more provision for the ventilation since the temperature of the body would not be enough greater than that of the surrounding air to create sufficient movement to carry the vitiated air away from the body. That is why a cool room does not require the same amount of ventilation that a hot room does.

Innate Intelligence is capable of adapting the heat of the body to a great range in atmospheric temperature, but in order to do this there must be a sufficient length of time to enable Innate to bring about the necessary adaptative changes in the body. If the atmospheric changes take place too rapidly this adaptation cannot be effected and the metabolic equilibrium of the body will be disturbed. This makes it necessary to exercise care in properly heating our dwellings.

Proper Temperature of Building

It is certain that temperature of the dwelling should be properly regulated and that it should not vary with the temperature outdoors, especially in the winter time. The heat equilibrium of the body may be easily disturbed by sudden changes in the temperature of the dwelling. Because there is an increased expenditure of the internal energy to bring about adaptation, the internal forces are dissipated and this lowers the resistance of the body and makes the individual susceptible to incoördination.

A high temperature with a relatively low percentage of humidity will cause an abnormal evaporation from the skin and mucous membrane. This gives not only a sense of chilliness but causes an abnormal dryness of the skin and produces an irritation in the throat and nose. On the contrary, the bodily heat will be withdrawn too rapidly in a temperature that is too low.

There are many factors to consider in determining the proper temperature of a room or a dwelling. The time of year, the processes carried on within the dwelling, the use of the rooms—that is, whether they are used for sleeping-rooms, living-rooms, or workrooms—all tend to influence the degree of temperature most advantageous to the inmates of the room.

In determining the proper temperature of a room the relative humidity that is to be maintained must be considered. A hot dry air is more desirable than a cool damp air. In winter the variation in the temperature of the average dwelling should be between 58° F. and 70° F. with a relative humidity of 40% to 60%. The temperature should be lower in the bedroom than in the living-room.

The great objection to the average heating system is that the air is kept too dry; therefore, it is necessary to keep the temperature of the rooms too high in order for the individuals to keep warm.

Requirements for Heating System

In order for a system of heating to meet the demands of hygiene there must be a minimum cost of production and absence of impurities produced in the process of heat; the heat must be equitably distributed over the house; the temperature must be kept even, thus insuring continuous heating; and there must be a proper degree of humidity. There must also be freedom from explosions and danger from fire.

There are three methods of heating; radiation, conduction and convection. There are two systems by which these methods are used: they are local and central. In local systems the heat is produced in the room by combustion or burning of fuel in grates and stoves.

In central heating the heat is produced at a central place outside of the rooms and conveyed to them by hot air, hot water or steam.

Even though these three methods of heating are usually given, it is difficult to draw hard and fast lines of demarcation between the different methods, for, as a matter of fact, they overlap to quite an extent. The element of radiation is involved in both conduction and convection.

LOCAL HEATING

Radiation

The vibrating molecules of a heated substance will set into motion the ether of space and in this way the heat may be transmitted as wave motion. We have an illustration of this in the transmission of heat to the earth from the sun. Ether waves are generated by the violent vibration of the molecules of the sun and the vibrations are transmitted to the earth and they in turn generate molecular vibrations of the bodies of the earth. This is spoken of as radiant heat and is illustrated by the heat from the open fireplace.

Open fireplaces give off heat by direct radiation. This is the oldest method of heating and has been in use for many generations. It is not a satisfactory method, however. The radiation of heat takes place through air very readily, but air is not a good conductor of heat. Heat may be radiated from the body very rapidly through the air to cold objects. As for instance, sitting near a cold wall one will feel chilly due to the radiation of the heat from the body to the cold wall, although the air in the room may be sufficiently warm to be otherwise comfortable.

Heat may be readily radiated from an open fire, but it must be remembered that the intensity of the radiated heat is inversely proportional to the distance of the heated object from the place where the heat is produced. To illustrate: If one object is one foot from the source of heat, the open fireplace, and another object is three feet from the fireplace, the object that is farther away will receive only one-ninth as much heat as the one nearer. This is one of the disadvantages of the open fireplace as a means of heating a room. A fireplace is very cheery and gives a room a comfortable appearance and is very popular in the modern home. It is adequate to take the chill away when the weather is not very cold, but it is certainly a very undesirable means of heating a house in cold weather.

Another objection to the open fireplace is that it requires a great deal of fuel. About 75% of the heat is lost through the chimney. There is, however, an advantage in the open fireplace since it affords an excellent means for ventilation; there is always a draft up the chimney.

Conduction

Heat is carried through such metals as iron by molecular action and such heat transference is known as conduction. The fact that heat is transferred through metals by conduction is of vital significance in the question of heat losses and dissipation, as through walls of buildings for example.

If heat be applied to any part of an iron bar or piece of metal it will be transferred to all parts of that iron by the molecular action until it is all heated. This can be illustrated nicely by placing the end of the poker in the furnace fire and in a short time the heat will be felt in the other end of the poker.

The stove is a good example of the conduction of heating. The heat is conducted through the iron of the stove to the air in the room, and then by convection through the air to all parts of the room. The molecules that are in contact with the fire first have their motion accelerated by the heat and this motion is passed from molecule to molecule until all the molecules in the entire iron are accelerated in their motion and thus the temperature of the metal is increased. Some metals are better conductors of heat than others, owing to the difference in the character of the connection between the molecules. Silver forms the best conductor of heat among the metals and is used as a standard of conductivity.

In conduction heat is produced inside a fire pot, as in a stove, and conducted through the iron then radiated from its outer surface. This is also called indirect radiation and is a more satisfactory method than the direct radiation since the material of the stove will retain the heat for a longer period of time and allow for its more equitable distribution. In this way it is possible to heat the room more evenly than with an open fire.

One of the objections to this method is that it is local and has all the disadvantages of a local heating system. The combustion takes place in the room and as a result there are certain amounts of impurities that are admitted into the breathing zone. There is the added disadvantage of having dirt and dust from the fuel and from the ashes and refuse from the process of combustion. These disadvantages are not encountered in a central system.

In extremely cold weather the stoves are likely to become overheated in an effort to keep the rooms warm, and overheated stoves not only increase the hazard from fires, but tend to scorch the air. Red hot iron consumes oxygen and gives off carbon dioxide which produces an unfit atmosphere for breathing. It is difficult to maintain an even heat in a room that is heated by a stove for the stove requires a great amount of attention.

CENTRAL HEATING

Convection

The most desirable system of heating is the central. In this system the heat is conveyed from the central heating plant to the rooms either by air, hot water, or steam. The heat may be produced in the house that is to be heated, usually in the basement, or it may be produced at a distance, as in the case of steam plants, and carried through pipes to the house. There are three principal systems of central heating: Hot air, hot water, and steam.

Heat is carried through air by convection. The air exposed to heat becomes specifically lighter and hence rises and the cooler air takes its place. In this way the air of a room is heated by its constant movement brought about by this phenomenon. The air becomes heated in the air jacket of the hot air furnace and creates an upward draft. As soon as the cool air rushes downward to take its place a downward draft is formed through the cold air ducts. In this way the air in the room is kept in circulation and at the same time properly warmed.

Hot air, or as it is sometimes called, furnace heating, is a very satisfactory system for an ordinary dwelling or small building. It consists of a large stove much as that used in local heating. Surrounding this stove is a jacket with an air space between it and the stove. Pipes lead from the air space through the top of this jacket and convey the air that is heated by the stove to the different rooms. The cold air is taken from the rooms and conveyed through the cold air pipes back to the furnace and is admitted to the air jacket from beneath. In this way the warm air, being lighter than the cold air, passes upward through the hot air pipes and is replaced by the cold air through the cold air pipes. In this way there is a constant circulation of air through the pipes.

This kind of a furnace requires much attention, but not as much as a local heating stove. Great care must be taken that the air is not overheated in the air jacket. If it is, the air in the room will be dry and stuffy and may even have a scorched odor. The furnace should be equipped with a water receptacle inside the air jacket. This receptacle should be kept full and in this way a proper relative humidity will be maintained. If this is not done, the air in the room will be too dry and it will require a higher temperature to keep the room comfortable. Another objection to this system is that dust and dirt are likely to enter the rooms from the furnace.

The hot water is a very desirable system of heating. Heat convection through water is practically the same as that through air. The particles of water at the point where the heat is applied become lighter as they become heated and because of this change naturally rise to the top and the particles that are cooler and therefore heavier sink to the bottom, thus forming currents. For this reason water heats much more rapidly when the heat is applied to the bottom than it does when heat is applied at the top of the receptacle. These principles are utilized in hot water systems. The hot water rises in the radiators and gives off its heat to the cooler atmosphere and the cool water returns to the boiler to be reheated. In this way there is a constant circulation of the water through the system.

The hot air system is entirely satisfactory for small buildings, but is not so desirable for large buildings. For large dwellings and public buildings the hot water system is much more satisfactory. In the hot water system a water jacket is provided instead of an air jacket. The water is carried from the boiler over the fire box through pipes to the different rooms where it passes through radiators and is returned to the boiler by continuous pipes. At the top of the pipes an expansion tank is placed to take care of the expansion of the water when heated. The heated water circulates freely through the system of pipes. Each radiator is provided with a valve to regulate the amount of water admitted and in this way the degree of heat may be regulated in the different rooms. Each radiator is provided with an air valve to allow the air to escape when the water is admitted, or to allow the steam to escape in case the system becomes overheated and the water is converted into steam.

This system is easily cared for and easily operated. It requires a relatively small amount of coal and maintains a very even heat, and when properly operated there will be no sudden changes in the temperature of the rooms. There is less danger of overheating the air and lowering the humidity with this system than with the hot air furnace.

The radiators may be placed in the rooms that are to be heated or they may be placed in the basement and the air admitted and passed over the radiator and warmed and then forced into the rooms. This is known as the indirect method and is used in connection with the system of ventilation. It is used more with steam than with hot water.

Heating by steam is by far the most satisfactory method, especially for larger dwellings and buildings. This system is somewhat like that of hot water, except the water is converted into steam. The temperature of the pipes and radiators is therefore higher than with hot water, but the pipes and radiators do not need to be as large.

Very often this system is used in connection with the ventilation. The radiators are placed in the basement or in another convenient place and cool fresh air from the outside is passed over them and warmed. It is then forced into the rooms. Very often this air is washed, as described in the chapter on ventilation, and thus freed from suspended matter. At the same time the relative humidity can be controlled and this is very essential, not only as a means of providing air that is most desirable for breathing, but also in point of fuel economy, since air of high humidity is more easily heated and is more desirable in conserving the heat of the body as has already been explained. Steam heating is especially suitable for high and irregularly shaped buildings. The fact that the radiators and pipes are empty when not in use reduces the risk of damage to the house furnishings from bursted or leaky pipes.

It is well to have the radiators placed near windows so that in ventilating the air will pass over them and be warmed before entering the room.