I live in a second floor apartment with a gas forced air furnace. The
furnace and water heater (both gas) are located in an interior closet.
In addition to the water heater and furnace flues, there is another 4"
pipe that comes through the ceiling and ends near the floor with only an
open elbow (not connected to anything). I assume this is a combustion
vent. Cut into the large duct coming out of the top of the furnace (is
this the plenum? -- sorry for my ignorance of HVAC terminology), there
is a large heating vent that serves only the closet. As a result, the
closet interior (being fairly well closed off from the rest of the
apartment except for about a 3/4" gap at the bottom), is always several
degrees warmer (or cooler, if the AC is running) than the rest of the
apartment. I have not measured the temp., but I would estimate that it
gets to be about 75-80 degrees in there when the thermostat is set to
65. It seems to me that this is at best an inefficient use of heat, and
I might get better performance by covering up the vent. Not being well
versed in all things HVAC, however, I have a couple of questions:
First, is there a legitimate purpose for having that vent in there? For
example, is it necessary for the combustion vent to function or
something like that? Another way to put this would be "will I run into
trouble by covering the thing up?" I have CO detectors installed, but
I'd sooner avoid producing a situation where they might go off than have
to figure out if they went off because of something I did.
Second, is covering the vent likely to have a noticable effect on:
a) performance of the heater (which is already not bad),
or b) efficiency of the system (which I am not thrilled with. It is,
according to the "EnergyGuide" label, near the bottom of the heap in its
class, as one might expect from a unit in an apartment where the
installer/landlord isn't paying the heating bill. Also, my heating bill
for December was seemingly extremely high for a one-bedroom apartment,
even considering an average temperature somewhere in the high teens or
Any help would be greatly appreciated. Thanks guys!