The Case for Indirect Heating 
PROPER HEATING AND VENTILATION ACCOMPLISHED BY WARMING A CONTINUOUSLY 
FRESH SUPPLY OF AIR—HOW THE FURNACE SUCCEEDS AND WHAT RADIATORS CAN DO 
By a Member of the Society of Heating & Ventilating Engineers 
Diagrams by the Author 
Editor's Note.— “What heating system shall I usef” is the constant query of the home-builder. To assist in solving his diMculty, House & Garden 
has had experts in heating engineering present the advantages of their own favorite types of apparatus. For the first time the whole case of the best 
heating method will be presented to the public as a jury. The last article was on hot-air; its predecessors were on steam and hot water. This is the 
final article in the series. 
I NDIRECT heating, like indirect lighting, represents an increase 
of cost over direct methods proportional to the decrease in 
intensity and the extent of diffusion; and, as the latter is a justi¬ 
fiable expense in the conservation of the optic nerves, so is the 
former in the preservation of sound lungs and their concomitants. 
The hygienic necessity of fresh air and the esthetic demand for 
freedom in the exercise of 
taste in decoration, require 
that as large a proportion as 
possible of all heating appara¬ 
tus space be placed outside the 
living rooms and that the 
means of contributing heat 
shall be invisible and effective. 
No universal rule is possi¬ 
ble in the premises, for what 
is “one man’s meat is another 
man’s poison,’’ and one set of 
scientific opinions or heating 
and ventilating platitudes, will 
appeal to the common sense 
of one individual and fall flat 
in the case of another. 
Until recently, considerations 
of hygiene alone have been 
sufficient to declare in favor of 
indirect heating, but indirect 
heating by the ordinary meth¬ 
ods is not the complete pana¬ 
cea for the ills of bad air. 
Recent discoveries point to 
the fact that keeping the air 
in motion is of greater mo¬ 
ment than the introduction of 
large volumes of outdoor air, 
and the aeration of the skin is 
of even greater importance 
than the right (theoretically) chemical composition of the air 
for breathing. 
Still one is by habit of thought strongly inclined to the estab¬ 
lished ethics of fresh air. In one particular, at least, suggested 
by the growing custom of smoking in most any of the rooms of 
the house, considerable fresh air is necessary to relieve the house 
dweller of the nausea of a second-hand smoke. 
On the side of esthetics there is no question but indirect heat¬ 
ing is the only solution. 
This method of heating, dependent as it is upon the introduc¬ 
tion of heat by the vehicle of air, absolutely relies for success 
upon some means to secure a constant flow of warm air into the 
rooms. 
The open fireplace which with the time-honored legends sur¬ 
rounding its history, without which there could be no Santa Claus, 
is still the central feature of decorative art in the home, and is at 
the same time one of the best means of assuring the success of 
indirect heating. But as to the room in which there is no fire¬ 
place, some means of relieving the room of its contents of air 
must be provided in order that the flow of air into that room, 
charged with the necessary heat, shall be positive and constant. 
Ventilation (a much abused word), or more accurately a means 
of exhaust, is the usual and uncertain solution. xA flue, or pipe 
called a flue, leading from the room to the outer air above the 
roof, if it is not too' small, if 
it is not too crooked, if it is 
properly installed, will some¬ 
times solve the difficulty — and 
sometimes it won’t. 
There are three conditions 
or characteristics of air in a 
flue — (a) when the outdoor 
air is sufficiently colder than 
the air in the house it flows 
upward; (b) when tempera¬ 
tures indoors and outdoors 
nearly coincide an equilibrium 
is established and stagnation 
of the air in the flue results; 
(c) when another flue in an¬ 
other part of the house for 
any or all of a dozen reasons 
has a stronger draught than 
the flue we are considering 
has a down draught, and like 
Artemas Ward’s ditch (high 
at the wrong end) the indirect 
system of heating will fail so 
far as that room is concerned. 
It is seldom realized to what 
an extent air leakage into or 
out of a room takes-place; 
but through walls of all kinds 
of material as well as around 
windows and doors a consid¬ 
erable passage of air is constantly taking place, with but very 
slight difference of pressure indoors and out: how else is it pos¬ 
sible that so many houses without a single fireplace or vent flue 
are warmed at all by means of hot-air furnaces. 
The one way to render indirect heating in the house successful 
is to have recourse to that modern agent which is now as familiar 
to us as was the wooden plow to the Egyptians, viz., electricity. 
The electric fan in the main air supply duct, running at a trifling 
expense and exerting just enough pressure to make a delivery of 
air through pipes, ducts and flues to all the rooms of the house 
simultaneously is the practical solution. 
A point to be considered in this connection is that in indirect 
heating the diffusion of the air throughout the house renders it 
highly important that all bath and toilet rooms should be heated, 
and by the direct method (radiators) ; that such rooms should be 
connected to flues leading to the outer air, so that the passage of 
air through or around the doors of such rooms shall be inward 
and not outward to other parts of the house, as would be the 
Indirect heating should provide an exit as well as an entrance for the air. 
The arrows show the circulation of the air in a typical system 
(34) 
