1908] Sanitary Conditions of Houses 37 



capacity takes place that it then will hold actually 7,0 grains, 

 or eight times as much. Now we have already referred to moist 

 air being four times a better conductor of body heat than dry air 

 is; hence, while outer air at zero heated and brought into a room 

 at 80° F. is made much drier and enveloping our bodies acts as a 

 non-conductor of body heat, yet it actually serves to rob the 

 body of its heat by its causing evaporation through insensilile 

 perspiration from the surface at so rapid a rate as to actually 

 produce a sensation of cold. Indeed, experimentally we know 

 that a room at 60° F.. with a relative humidity of 70% approaches 

 the happy medium of comfort and wdth no air currents occurring 

 in the room lends to persons sitting still a sensation of bien ctre 

 perhaps greater than any other temperature. It is further most 

 important, from the standpoint of economy, since it is found 

 especially in cold weather-,- that just as radiation is proportion- 

 ately rapid in proportion to the difference in temperature be- 

 tween two bodies, so every extra degree of increased temperature 

 required of a furnace means notably more coal consumed. 

 Indeed, as much as 25% more coal it is estimated is required to 

 maintain 70° F., instead of 60° F. in say zero weather. 



It is, however, important to remember that into this heating 

 problem other most important factors enter. Thus a single 

 window radiates heat probably 25 times as fast as would double 

 windows with tight space of air say 6 inches in thickness. Hence, 

 a double window is a sine qua non to effective heating and ventila- 

 tion in a cold climate. But more than this, a great difference is 

 found in the radiation of heat between the north and south sides 

 of a house, in cold weather. In the cold weather during the day the 

 sun streams in the south windows by radiant heat warming all 

 the walls as well as the air of the rooms. The north side is never 

 so warm; but on the contrary, is exposed to the northerly winds 

 which are found to rob surfaces of heat directlv in proportion, 

 not alone to their temperature, but also to their velocity. We 

 thus have illustrated how many factors enter into the heating 

 of even a small house. But we have said nothing of how in keep- 

 ing the house warm we mav also maintain its air fresh. One 

 thing is quite clear, viz., if we exhale some 2 lbs. of carbonic acid 

 in 24 hours, due to inhalation of oxygen (3 lbs.) and to tissue 

 combustion that placed in a box sealed hermetically we would 

 gradually exhaust all the oxygen or be poisoned by the carbonic 

 acid and other volatile emenations from the body. Clearly 

 we require to introduce fresh air and its oxygen, estimated to be 

 at the required rate of 2,000 cubic feet of fresh air per person 

 per hour. Naturally, when we do this, we must push out the 

 foul air and so it comes about that we must by some simple 



