HEATING AND VENTILATION 



2751 



HEATING AND VENTILATION 



HE AT 'ING AND VENTILATION, ventila' 

 shun. Heating is the process of keeping living 

 rooms at such a temperature that they may 

 shelter human beings in comfort. Ventilation 

 is the means by which the same space is sup- 

 plied with fresh air in such measure and by 

 such means as shall be conducive to continued 

 health. To state it somewhat more pointedly, 



the object of heating is not only to make a 

 building or a room warm, but to make it 

 healthful; while the object of ventilation is 

 to keep it healthful. The principles upon 

 which these arts depend are so mutually in- 

 volved that they are considered as one sani- 

 tary and engineering problem, and will be so 

 considered in this article. 



The Heating Problem 



The human body needs to be kept at a 

 temperature of 98.2 F. in order to sustain 

 life processes; it loses heat in a cooler medium, 

 the same as any other kind of matter. Food 

 in proper chemical proportions creates heat, 

 and clothing helps the body to retain it; a 

 person can therefore live in comfort in tem- 

 peratures considerably below body' heat. In 

 Northern Europe people are accustomed to a 

 temperature a little below 60, while in the 

 United States and Canada about 68 to 70 

 is usually demanded. The thermometer marks 

 56 as "temperate," and doubtless those people 

 who accustom themselves to such a tempera- 

 ture are more robust than others who insist 

 upon warmer air in their rooms. 



The tendency of masses of air at different 

 temperatures is to equalize their temperature. 

 Consequently the air in a room artificially 

 heated tends to lose heat until it reaches the 

 temperature of the outside air unless addi- 

 tional warmth is continually supplied. The 

 rapidity with which the heated air escapes is 

 also an important factor in maintaining the 

 temperature. If it escapes freely the tempera- 

 ture of the room is lowered more quickly than 

 if it escapes slowly. Heat is lost through win- 

 dows ; three-fourths of what is lost in that way 

 could be saved by double windows. A fire 

 creates air currents, and much heat is lost by 

 such means before it can affect the tempera- 

 ture; some escapes through cracks around 

 doors and windows, and more by proper ven- 

 tilation. It is the problem of the householder 

 to provide sufficient heat to offset these losses 

 and maintain an even, healthful temperature; 

 when one has done so he has practically mas- 

 tered the science of heating. 



The temperature of a room is raised in 

 either of two ways. One method, known as di- 

 rect radiation, is the heating of air already in 

 the room by means of stoves and fireplaces, 

 or by radiators connected with pipes which 

 conduct hot water or steam produced in fur- 

 naces. The other, indirect radiation, consists 



in bringing into the room air which has been 

 warmed by being passed over a central heated 

 surface, such as a coil of steam or hot-water 

 pipes. 



The commonly-used hot-air furnace provides 

 warmth by means of indirect radiation, for 

 the air is first heated by circulating between 

 the inner part of the furnace, where the fire 

 burns, and the outer casing, and is then con- 

 veyed through large pipes or flues to the vari- 

 ous rooms, which are provided with registers. 



HEATING BY FURNACE 



(a) Furnace, with pipes running to all rooms 

 of the building, (b) Chimney. ( c ) Cold-air en- 

 trance to furnace from outside. The arrange- 

 ment of pipes in a system employing steam or 

 hot water is substantially the same, each pipe 

 running to a coil of pipes in a room, such coil 

 being known as a radiator. 



The hot-air furnace provides both heat and 

 ventilation, for a supply of fresh air from out- 

 of-doors is being continually brought to the 

 furnace through a duct which connects with 

 the outer casing. The indirect method of heat- 

 ing is the more sanitary of the two systems; 

 direct radiation may warm air which is already 

 foul and thus prove a source of danger to 

 health. 



The drying tendency of any heating appli- 

 ance should always be considered. The air in 

 a room cannot be healthful unless it contains 

 a certain proportion of moisture, and in homes 



