BUILDING NEW HOUSES 71 



THREE SYSTEMS OF HEATING HOT AIR, HOT 

 WATER, AND STEAM. 



Heated air passing directly from outdoors to the 

 rooms to be warmed is the ideal heat if it is not passed 

 over a too hot surface which burns the air as in the ordi- 

 nary hot-air furnace. The indirect hot-air heat is pro- 

 duced by passing cold air from outside over surfaces 

 of hot water or steam-heated pipes, and is not open to 

 the objection of the ordinary hot-air furnace, but the 

 cost of heating by this method is much greater. An- 

 other objection to a hot-air furnace is that we cannot 

 always direct the heat where it is most needed under all 

 conditions of weather. 



Hot-Water Heat. 



Heated water distributed through small pipes to 

 radiators or stacks in the rooms to be heated gives a 

 very economical and pleasant heat. It can be carried 

 to the exact point where needed and little or much heat 

 may be produced, according to the extent of radiating 

 surface or the temperature of the water. Two kinds of 

 boilers are used for water heating the wrought-iron, 

 with tubes, and the cast-iron boilers of many different 

 forms. The wrought-iron boiler is generally considered 

 the most economical of heat while new and if kept clean, 

 but in moist cellars scales of rust soon form on the 

 inner surface under which are air-spaces that keep the 

 heat from coming in contact with the inner or water 

 surface of the boiler, and after a few years the boiler will 

 need renewing. 



Cast-iron boilers may be used with less risk in wet 

 cellars, as the surface does not rust in scales and the 

 heat will pass through the rusted iron almost as readily 

 as if it were new. 



