answered an insulation question in this column not too
long ago, and Joe Ponessa sent me an email in late
November about it.
don’t think you gave enough attention to the issue of
combustion (makeup) air," said Ponessa, professor
emeritus of housing, indoor environment and health at
Rutgers Cooperative Extension.
agreed that the limited work I described did not sound
as if it would cause a problem for
"atmospheric" combustion appliances, which
derive their air from the surrounding environment.
is, however, "a tipping point where draft-stopping
will prevent adequate combustion air when all combustion
appliances are operating simultaneously," Ponessa
said. For this reason, "my colleagues who
specialize in energy state that all weatherization
projects should include a backdraft test to assure that
combustion gas spillage does not occur."
noted that he didn’t know where the line might be
drawn between modest draft-stopping and that serious
enough to warrant back-draft testing.
expert should be able to offer some insight into this,
he said, and "I think it would be a beneficial
follow-up for your readers.
the way, I think that in most homes, air-pressure
irregularities in the basement — driven by heating,
ventilation, and air- conditioning equipment — will
communicate to the upper floors, and certainly if there
are ductwork registers — or duct leakage — in the
basement," Ponessa said.
an idea of the dynamics involved in airflows and
exchanges, he offered the following example:
oil burner, at a firing rate of one gallon per hour,
draws about 1,600 cubic feet of air per hour; typical
range hoods, about 200 to 400 cubic feet per minute.
a house is "too tight," those units will
compete for replacement air.
resulting negative pressure will cause combustion
spillage in the weaker appliance, he said.
of heating, don’t forget to have your furnace checked
out by a professional before winter gets any older.
least change the filter, following manufacturer’s