"_The House_ [_of Commons_] _met to-day_ [_27th April_] _after the
Easter holidays--and honourable members, on entering, seemed highly to
appreciate the unusual luxury of a little fresh air._"--THE TIMES, 28th
April.
The failure of some late attempts to ventilate public buildings invites me
to set forth an _Encyclopædia of ventilation_--at a cheap rate, and in a
compendious form.
Aware of the abilities and celebrity of many of the writers on this
subject--from Whitehurst and Franklin to Reid and Gurney--I must ward off
the imputation of self-conceit by expressing my belief that the errors of
those who have failed should be chiefly ascribed to excessive cleverness;
to unadvised attempts at outwitting nature! I hope to escape that snare. In
the execution of my humble task, I shall entirely rely on common sense and
common experience.
Air is essential to human life, and as respiration destroys its vital
qualities, the _ventilation_ of rooms which are intended for habitation
should be a primary object in all architectural plans.
Architects, however, seldom provide for the ventilation of rooms otherwise
than as they provide for the admission of light. Now the properties of
light and air, with reference to our domestic requirements, differ in some
important particulars--of which it may not be amiss to give a brief
enumeration.
_Light_ moves with uniform velocity: _air_ is sometimes quiescent, and
sometimes moves at the rate of thirty miles an hour. _Light_ diffuses
itself with much uniformity: _air_ passes in a current from the point of
its entrance to that of its exit. _Light_, whatever be its velocity, has no
sensible effect on the human frame: _air_, in the shape of a partial
current, is both offensive to the feelings and productive of serious
diseases. _Light_, once admitted, supplies our wants till nightfall: _air_
requires to be replaced at very short intervals. _Light_ may be
conveniently admitted from above: _air_ requires to be admitted on the
level of the sitter. _Light_, by the aid of ground glass, may be modified
permanently: _air_ requires to be variously adjusted according to its
direction, its velocity, the seasons, the time of the day, the number of
persons assembled, &c.
An attentive consideration of the above circumstances leads me to certain
conclusions which I shall now state aphoristically, and proceed to describe
in more detail.
A room designed for a numerous assemblage of persons--as a reading-room, a
lecture-room, or a school-room--should be provided with apertures, adapted
to admit spontaneous supplies of fresh air, in such variable quantities as
may be required, on at least two of its opposite sides, and within three
feet from the floor; also, with apertures in the ceiling, or on a level
therewith, to promote the exit of the vitiated air. The apertures of both
descriptions may be quite distinct from those which admit light.
Suppose a room to be twenty-four feet square, and sixteen feet in height,
with two apertures for light on each side, each aperture being three feet
wide by eight feet in height, and rising from the floor. There are not many
rooms constructed on a plan so favourable to the admission of fresh
air--but it has some serious defects. 1. The air would enter in broad and
partial currents. 2. It would not reach the angular portions of the room.
3. The vitiated air might rise above the apertures, and so accumulate
without the means of escape.
Now, suppose the same room to have its apertures at eight feet from the
floor, and so to reach the ceiling. The escape of the vitiated air might
then take place--if not prevented by a counter-current. But whence comes
the fresh air for the occupants? There is no direct provision for its
admission. The elevated apertures are utterly insufficient for that
purpose; and _the perpetual requisite is no otherwise afforded than by the
occasional opening of a door!_
It being thus established that the same apertures can never effectually
serve for light and ventilation, I propose with regard to reading-rooms,
lecture-rooms, and school-rooms, which require accommodation for books,
maps, charts, and drawings, rather than a view of external objects, that
the windows should be placed in the upper part of the room--that the
admission of fresh air should be provided for by ducts near the floor--and
the escape of the vitiated air by openings in, or on a level with, the
ceiling.
The number of windows, and their size, must depend on the size of the room.
If windows are to admit light only, a smaller number may be sufficient, and
they may not be required on more than one side; a circumstance which
recommends the plan proposal, as we can seldom have windows on each side of
a room, or even on two of its opposite sides, but may devise a method of so
admitting air.
Rejecting the use of windows as a means of ventilation, and rejecting
artificial currents of every description, I propose the substitution of
air-ducts of incorrodible iron, to be inserted horizontally in the walls of
at least two opposite sides of the room, within three feet from the floor,
and at intervals of about four feet. The ducts to be six or eight inches in
diameter, according to the size of the room. The external orifice of each
duct to be formed of perforated zinc, and the internal orifice, which may
be trumpet-shaped, of {416} perforated zinc or wire-gauze, with a device
which would serve to adjust the quantum of air according to circumstances,
and to exclude it at night. By such contrivances, while the offensive and
noxious currents which proceed from wide openings would be obviated, the
supplies of fresh air would always be equal to the demand. The _purest_ air
may not be accessible--but, as Franklin says, "no common air from without
is so unwholesome as the air within a _close_ room."
The escape of the vitiated air requires less consideration. If the ceiling
of the room be flat, with another room above it, the upper part of each
window, in the shape of a narrow slip, might be made to act as a sort of
safety-valve; but if the windows are on one side only, corresponding
openings should be made on the opposite side, so that there would almost
always be, more or less, a leeward opening. A vaulted ceiling, without any
other room over it, seems to be the most desirable form, as the vitiated
air would rise and collect towards its centre, where there could be no
counter-current to impede its egress.
It is the union of those two objects, the admission of fresh air and the
riddance of the vitiated air, skilfully and economically effected, which
forms the circle of the science of ventilation.
I have restricted myself to the means of _ventilation_, which is requisite
at all seasons of the year, but am quite aware that _warmth_, or a
temperature above that of the external air, is sometimes indispensable to
health and comfort, and therefore to the free exercise of the faculties. I
believe, however, that the means proposed for the admission of fresh air
might also be made available for the admission of heated air, and that
either description of air might be admitted independently of the other, or
both descriptions simultaneously.
A vast increase of reading-rooms, lecture-rooms, and school-rooms, may be
safely predicted, and as the due ventilation of such rooms is a project of
undeniable importance, I hope this note, eccentric in form, but earnest as
to its purpose, may invite the remarks of others more conversant with
architecture and physics--either in correction, or confirmation, or
extension, of its general principles and details.