1. Fireplaces and stoves. - (A.) The heating of a building is not a part of the work of a carpenter, but he should have some knowledge of the different methods of heating in common use.

Our forefathers used fireplaces for both heating and cooking, but as far as heating is concerned, they are unsatisfactory, as the room quickly cools off if the fire dies down. They are invaluable in the fall and spring, before and after it is necessary to heat the entire house, and as an auxiliary to the heating system during an extremely cold spell.

A fireplace furnishes a valuable means of ventilation, and thus adds much to the healthfulness of the house, besides imparting an air of cheerfulness. The center of the decorative scheme of a room is generally the fireplace and mantel.

(B.) Stoves are efficient as heaters, and may be regulated to radiate as much or as little heat as desired, within the capacity of the stove. They are inconvenient, and cause much dirt to be brought into the room.

2. Hot-air heating. - (A.) A system of furnace heating properly installed usually gives satisfaction, though there is an economical tendency to put in a furnace which is not quite large enough for extremely cold weather.

The furnace should be set low, and accordingly is often placed in a pit in the cellar, in order to give as much pitch to the conductor pipes as can be obtained, since a pipe with less rise than one inch to each foot in length is very apt to conduct heat unsatisfactorily, though the pipes leading to the upper floors of a building will give satisfaction with less pitch than those which heat the lower floor.

The furnace should be located very near the center of the system, but nearer the side of the house from which the prevailing cold winds come, to give as much pitch as possible to pipes running in that direction, which rarely conduct the heat as satisfactorily as others. These conductor pipes should be connected at the furnace upon the same level, or the highest pipes will take most of the heat and destroy the efficiency of the others. The conductor pipe leading to a room which is difficult to heat is sometimes placed above the others, but not unless it is very necessary.

(B.) A cold air duct of about half or two thirds of the capacity of all the conductor pipes it is to supply should connect the furnace chamber with the outside air, by means of which, pure air is heated before being used to heat the house. This cold air duct should be provided with a damper or slide, by which the air supply may be regulated; if the best results are desired, ducts should be taken from opposite sides of the house, as the direction of the wind often has considerable effect upon the efficiency of a furnace.

A register sometimes is placed in the floor or wall for the purpose of conducting impurities out of doors; this formerly was a common custom in the best houses, but is not used so much at the present time, as partly heated air is wasted, and the expense of heating a house is increased. Instead of allowing this air to pass out of the house, it is usually conducted to the furnace chamber and reheated, and enough pure cold air allowed to enter the furnace chamber at the same time, to replace the vitiated air. From the standpoint of theory this is not desirable, but in an ordinary dwelling there are not enough impurities to make this method hygienically objectionable, as the opening of the doors and the crevices of the house will allow enough pure air to enter to make the air in the house suitable for use.

Since most of the impurities in the air are burned out by contact with the furnace drum, and since greater efficiency of the furnace is obtained at less cost, this method is being installed in nearly all of the best furnace-heated houses now in construction, and many are being remodeled to allow this system.

It is important that furnace pipes should be carefully wrapped in asbestos paper to retain the heat and to conform to insurance regulations; pipes which go in the partitions should be put in place before the house is lathed.

(C.) In a modern furnace, there is provision made for a water pan in the air chamber. The water becomes heated to a moderate temperature, so that moisture is given off by evaporation, and carried through the house by the movement of the heated air. Unless moisture is supplied, the air will be so dry that it not only is undesirable for breathing, but will cause the joints of the finish and of the furniture to open, the frame of the building to shrink so much that the plastering will crack, and the doors to warp and shrink so badly that they will not latch.

3. Steam and hot-water heating. There are three methods of heating, by some one of which all steam or hot-water heating apparatus is operated.

(A.) The term direct heating is applied to the system in which heat radiates from coils of pipes or radiators directly into the room in which the appliance is located.

This method is used in places where little attention is paid to ventilation, though it should not be installed where there are to be many people, as the same air is simply heated over and over again.

(B.) The term indirect heating is applied to the system in which fresh air is heated by being passed through steam or hot-water radiators located outside of the room which is to be heated. Though not often so regarded, a hot-air furnace is an example of this system, as the outside air is heated before it is conducted into the room.

In this method of heating, a system of ventilation is frequently installed in connection with the steam or hot-water system, by which the impure and cold air is removed at the floor level, giving place to heated fresh air.

This method is sometimes applied by connecting the foul or cold air ducts with the heating coils, as described in furnace heating, and by allowing this partly heated air to be reheated more economically than if cold air were heated to the desired temperature. It is obvious that this system, which is in effect direct heating, is objectionable where many people have to breathe the same air over and over. This objection is to some extent removed by the introduction of a certain amount of fresh air to the heater to replace some of the vitiated air, as by the indirect method. (See the preceding page.)