HEAT LOSS
No matter what you do, when it is 68° F
inside your house, and 0 degrees outside your house; the cold will suck the heat out of
your house. It will pull at a certain rate through the exposed walls and ceilings, through
the windows and floors. This is known as heat transfer.
The cold air is also trying to sneak into
the building through every little crack in every nook and cranny. This is known as
infiltration. Your heat, on the other hand, is trying to escape through every nook and
cranny. This is known as exhilation. It's as if the house was breathing. Breathing both
air and temperature in and out.
The total of all this leaking and losing at
a specific low temperature for your region, is known as the heat loss. This total will be
calculated in btu's per hour, and the heating system will need to produce and distribute
this same amount of btu's per hour to maintaint your 68° F room temperature. As most
rooms differ from one another, each room's heat loss must be determined. The total loss of
all rooms added together will determine the size and design of the heating system.
In simple structures, the mere replacement
of this lost heat is sufficient; but in complex houses with open floor plans and multiple
levels, the flow of heat within the building becomes a factor. Heat rising from the first
floor to the second, increases the demand on the first floor while decreasing the demand
on the second.
The formula used here is a combination of
three ingredients developed to reflect the internal conditions of a modern structure. It
combines industry accepted standards of heat transfer with the old fahioned tin knocker
"cfm method" of computation ; blended together by 25 years experience designing
and installing heating and cooling systems. The result is an estimate of comfort.
In the heat loss calculation, all windows
are created equal, no matter which direction they face. Disallowing for wind
factors, similar types of glazings lose heat at the same rate. On the other hand,
when calculating heat gain, windows facing east and west gain more heat that those facing
north and south. This results in larger quantities of air being distributed to rooms
with east and west facing windows. This air is necessary for cooling but not for
heating. In the more northern climates, where heating is a priority, enter all
window areas as east and west shaded, regardless of which direction they face.
This will restore the emphasis on a balanced distribution system rather than one
weighted toward solar radiation.
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to Heatload Workshop |
