45 
Warming and Ventilating Buildings. 
be avoided. The modern mode of finishing rooms is not well 
adapted for admitting fresh air, as it seems to have been a direct 
object of research to exclude it. But it is only necessary to pro- 
vide the means of warming fresh air before it enters, during the 
winter season, and then the motive for excluding air is done 
away, and the same channel may supply it in summer, when it 
becomes as agreeable as it is necessary. 
When workmen were less skilful, our apartments had a plen- 
tiful supply of air, and the want of ventilation was never felt ; 
but now that walls are rendered impervious to the air by plas- 
tering, and floors are made double, and doors and windows are 
fitted with scrupulous accuracy, the consequent decrease of the 
fresh air admitted, renders it necessary to attend to ventilation, 
which formerly there was very little reason to provide for. Yet, 
it must be admitted, that, with a system of ventilation which we 
can regulate, in respect to quantity, at pleasure, rooms must be 
more comfortable than when the wind entered on every side, 
and could not be excluded. When one improvement is effect- 
ed many others become evidently desirable ; it is thus that art 
has made such rapid strides of late years ; but the improvement 
in the construction of buildings has been slow, compared with 
that in some other arts, and the effect of close rooms on health 
has not been so soon nor so distinctly perceived, as one would 
have expected. The comfort of a warm room is sought for 
much more than that of a pure and healthy atmosphere. 
It has been shewn, that there ought not to be less than four 
cubic feet of air removed per minute by ventilation for each in- 
dividual in a room * ; and in the same work the following rule is 
given for the area of the ventilators through which the heated air 
is to ascend. Let N be the number of people the room is intend- 
ed to contain, h the height from the floor of the room to the top 
of the ventilator tube in feet, T the temperature of the internal 
air, and t the temperature of the external air ; then, 
— the area of the ventilator in feet. 
It will be obvious, that the largest ventilation is required 
* Principles of Warming and Ventilating Buildings, p. 72. Lond. 1824. 
N /450 + T 
75 V A(T — 
