Duct Leakage in Forced Air Systems
Not many studies have been performed about effects of duct leakage in non-residential buildings. For residences, studies of the duct system have been performed for some time. Here are two quotes from such studies relating to some of the problems:
... Field studies have shown that, on average, duct leakage accounts for 15% - 30% of heating and cooling costs, depending on the location of the duct system ...Modera and Byrne, Home Energy, Jan/Feb 1997
... Leaky ducts fill house with fibers, leave youngsters with lung disease ...Glassroots of Cancer, Vol. 7, No. 3, 1996
Q&A
How can one reduce the effect of duct
leakage?
Duct leakage has its biggest effect if temperature
differences between the air flow inside the duct and the ambient is large.
At a given leakage rate, ducts being used for forced heating and cooling
will produce higher energy losses than ducts for ventilation systems.
What are the other effects of duct
leakage?
Leaks in the return ducts (or the return plenum)
pick up pollutants from the zones they are placed in. This could bring exhaust
fumes from garages or VOCs from storage spaces into the occupied spaces.
Air not being supplied to the desired space reduces the ventilation and/or
conditioning effect and requires more air to be thermally conditioned and
also increases the fan energy. Best practice is to provide thermal energy
by means of hydronic loops (e.g., install Hydronic
Radiant Conditioning)
This page was developed at IES by hef. Last changed on July
13, 1997
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