Heating, Ventilation and Lighting 



195 



will leak slightly. In the case of the fireplace being used as the floor 

 duct, the top duct should not be placed above it. It may be in another 

 inner wall or in the centre of the ceiling (as the centrepiece), but never above 

 a source of heat or in the outer wall. 



In the above calculations we have 

 not considered the direct radiator, as 

 it is best to use it in such rooms as it is 

 necessary to fit with a fresh-air inlet. 



In order that one may form some idea 

 of the necessary units to be supplied in the 

 heating and ventilating of a house, certain 

 principles and assumed conditions must 

 be borne in mind in order that a basis of 

 rough calculation may be arrived at. 



Air, whether in the room to be heated 

 or introduced into it through ducts, is 

 warmed by an agent considerably higher 

 in temperature than that desired for 

 the room. Heated air loses by radiation 

 from the walls of the enclosure into 

 which it is introduced. Hot air, rising, 

 moves faster and with less friction through 

 a vertical than through a horizontal duct. 

 Exposure to cold winds affects the tem- 

 perature of a room, owing to unavoid- 

 able leakage and contact of air with cold 

 walls. This leakage is about equal to 



the Cubic Contents of the room per hour. A good fireplace of tile. A suggestive example, but TOO 



Although the leading authorities differ mu < h crowde H d . by the flankinB doors ' and out of harmony 



& f f with surroundings 



considerably, it is generally considered, 



however, that 1,800 cubic feet of fresh air per hour be allowed for the use of 



each person; Baldwin places it as high as double this amount. 



The normal temperature for artificial heat is usually placed at 70 F.; 

 the low external temperature for this climate (New York) at zero F. For an 

 average condition of walls and windows with light on two sides, to heat to 

 70 F. at zero weather, hot air should be introduced at 100 F. Add 10 per cent, 

 to heating power for exposure to prevailing cold winds. A rough estimate of the 

 size -of furnace pipe required to heat an ordinary room to 70 F., external 

 temperature at zero F., may be made by allowing I square inch in sectional area 

 of pipe to each 20 cubic feet of space to be heated. 



Owing to the awkard obstruction offered to the passage of air through the or- 

 dinary register by the perforated ornamentation, at least one-third increase in area 

 should be allowed over that of the connecting air-duct. While the velocity is de- 

 creased in its passage through this ornamentation, the increased area makes the total 

 discharge about equal to the uninterrupted discharge. Hence there is no reason 

 why the registered-covered opening should not work as well as the free opening. 



