Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1889-06-18
The Vacuum and the Plenum Methods.

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The Vacuum and the Plenum Methods
| The Vacuum method effects a movement
OF air into a room by creating partial
vacuum within IT, The air then flows into
the room through every available channel
both provided and accidental. Just a. all
supplied 10 q room under slight pressure will
ind its escape, in large quantity, from the
rsom, though sealed as tigh, as putty. paint,
paste and paper can seal it, so outside air
will as freely leak into such room when a
vacuum condition is maintained ~ilhin it
| The undesirable results are several.
l. The inward leakage Of cold outside
air, settling to the bottom Of the room, end.
to produce chilly foo- This in turn make :
il necessary TO heat the air of the room
enough higher to bring the temperature of
the floor up to the point OF comfort, or a
superheating of the air 10 the upper part of
the room for the rake Of omfortshle
warmth in the lower part This results in a
greater temperature difference between the
ceiling and the toor than would exist without
| the inward leakage of cold air That is, the
chilly floor necessitates the maintaining of a
higher mean temperature within the room
ture to the point of comfort, than would be
otherwise required. The Consequence is an
increased consumption of fuel over that
which would be required were the tempera
ture uniform from floor 10 ceiling This de-
feet with the exhaust method is identical with
that peculiar to and inseparable from the use
Of the old fashioned FIRE place. IL is the
more defective as the climate in which ii is
used is colder AMI the ma ntained vacuum
greater.
?. Another result attending the use of the
vacuum method is that, unless all outlets iu-
cludlng IRE places, etc are connected with
the exhaust system, the vacuum condition
within the room tends to retard and to re-
verse the desired flow through hues. Fire
places are more likely to smoke. and other
independent fues to be weakened or re-
versed.
3. The source of a rooms supply is not
as completely under the control of the occu-
pant as in the plenum method. The air
moves from greater and toward lesser
pressure. From whatever point, therefore,
the pressure may be greater than IN the
room, from hat point it will move toward
the room. reduction of the vacuum, or
what is the same thing, an increasing of the
pressure in adjacent rooms or parts of the
building, as by the opening of windows and
doors, or the shutting of the exhaust hue re-
suits in air movements toward the room in
which the vacuum is maintained. Each
room is therefore, more or less at the mercy
of its surroundings, and of conditions be-
yond the control of its occupant.
I Inrushing air is felt as a current by
those within room very much more than an
out rushing current of the same volume
An in-rushing current is concentrated in vol
ume diverging slowly. and maintaining its
high velocity to considerable distance
from the point of inlet An out-rushing
current, being strongly convergent toward
the outlet in its movement from every posi-
BILE point of approach, becomes insensible as
draught only on near approach to the out
1t.
Because of the relatively large volume of
air to be moved through an audience room
and the necessary energetic action of
the exhausting apparatus. the vacuum within
il is generally greater than that without it,
when ventilated by this method The open
ing of doors into the corridors OF lobbies is
then attended by an in rush of air.
The Plenum method of ventilation on the
other hand, puts each room under slight
pressure, and retards or prevents inward
leakage of cold air, and renders more posi-
bic that uniformity of temperature within a
room which is essential to the highest econo-
my in the use of heat; Il tends to accelerate
rather than retard the flow of air through
vents, as tireplaces, etc it gives an occu
pant of a room control over the source of
his air supply; and it results in an outward
flow through open doors.
For these reasons | have no hesitation in
recommending the Plenum rather than the
vacuum method for your use in the propos-
ed ventilation of the capitol.
The vacuum method is as much better for
certain kinds of work a. is the Plenum for
others. as in the production of concentrated
ventilated draughts through hoods etc. or
in giving direction to slowly moving air freely
supplied to building for distribution by
means of corridors, stair wells and open
doors The greater vivacity sometimes at
trjbuted 20 air supplied by the vacuum meth
od. if it exists at all NAV be due in part to the
process going on within the room of the
mixing of cold inward leakage with the
warmer air of the room. Monotony is as
depressing as variety is refreshing inform
ly warmed and quietly moving air at 20 de-
gre.s will doubtless have different and less
pleasing feet than bodies of air at 80 de-
grees and - degrees lmperfectly mixed and
in active movement. The depressing effect
said by its opponents to be insepsrsble from
plenum ventilation is, however, more likely
due to the faulty way in which the air supply
is heated