22 



HEAT 



confining the radiators to the basement, to which cold air 

 from outside is constantly admitted in such a way that it cir- 



FlG. 16. Fresh air from outside circulates over the radiators and then rises into the 

 rooms to be heated. 



culates over the radiators and becomes strongly heated. 

 This warm fresh air then passes through ordinary flues to the 

 rooms above, as in Figures 16 and 17. 



ii. Fresh Air. Fresh air is essential to normal healthy 

 living, and 2000 cubic feet of air per hour is desirable for 

 each individual. If a gentle breeze is blowing, a barely per- 

 ceptible opening of a window will give the needed amount, 

 even if there are no additional drafts of fresh air into the room 

 through cracks. Most houses are so loosely constructed that 

 fresh air enters imperceptibly in many ways, and whether we 

 will or no, we receive some fresh air. This supply is, how- 

 ever, never sufficient in itself and should not be depended 

 upon. At night, or at any other time when gas lights are 

 required, the need for ventilation increases, because one gas 

 burner uses up the same amount of air as four people. 



