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 On the contrary, the bodily heat will be withdrawn too rapidly in a temperature that is too low.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.