Furthermore, beyond the duty of the heating plant, it has been the great civilizing influence in the life of man. Wherever the heating plant has gone, there has man been able to regulate his work, play and goings and comings. In this way health has been better maintained and more regularly in work, therefore, continuous endeavor which, of course, spells advance and civilization. Not wishing to deprive heating engineers of their profession we shall not drag you through tortuous technical pipes and valves, but simply tell you what you must demand in a heating installation.--Here, unless you are properly equipped you will add to the junk pile in quantity and therefore waste your money by the wholesale. First: you must decide whether you really want _hot air_ or furnace heating. In this case the furnace heats the air and it rises through a register in the floor or wall of your room. According to J. Byers Holbrook, the distinguished heating engineer, this sort of heating tarnishes your silver, your bookbindings crack and your lungs are made either immune to poison or function in spite of the “rich air” reaching them. In this place it is wise to mention the pipeless heating system which is hot air sent from the furnace to one central vent or register which is supposed to heat the whole house. It can be used only for small houses. It is very cheap in comparison to other systems, but it is unsafe. (See the safer method further along in this chapter under “Bungalows.”) It is unsafe; for example: If there be illness in one room it has to be open to be heated therefore disease will be spread. Furthermore rooms that are closed will get no heat, as the door must be open to receive the hot air. Second: there is steam heat. This is an excellent system well adapted to residences and buildings, hotels, institutions, business houses, etc. Third: Vacuum and Vapor, the steam circulates through the system at practically atmospheric or greatly reduced pressure. Vapor heating is used in residences, vacuum heating is used mostly in large buildings. Fourth: Hot Water, which is probably best for your purposes. And with these deterring and encouraging words we will launch directly into what you should know before installing a hot water heating plant. THE HEATING ENGINEER There is such an “animal” as the heating engineer. He it is who can tell you to an iota how much heating surface you have in your home to be heated. He it is who can subtract and add footage and finally tell you whether you must heat 4400 feet or 3000 feet. When you know this, of course, you can more readily order the boiler which is best adapted to heat such a surface. For example, suppose you had a conservatory in one end of a large room--your heating engineer could tell you--due to the glass surface--how much more heat was required for this room, even had you no flowers for your conservatory. Glass windows in a shop or in any room add to the heat units required.