We want to remodel our kitchen, but a large 9" round chimney vent to
our roof connected to our furnace and hot water heater runs through
one of our cabinets, taking up a fair amount of space. In the
remodel, we are putting in a new wall to separate the kitchen area
from the dining area that is next to the existing chimney.
A handy friend of mine said that I could convert the round pipe to a
rectangle (3 x 10) that could run through the drywall. However, the
heating contractors I've spoken with on the phone are saying I can't
do this and I need a new furnace and hot water heater to direct-vent
the air out.
My concern is that these heating contractors are mostly trying to sell
a product rather than really telling me what I could do more
economically. I'm also concerned that if I follow my friend's advice,
I might not be up to code (and could potentially endanger my
I'm not very handy and would appreciate any advice.
They are correct. I don't believe this would be a safe venture.
Flue venting is very important to your family's safety. Depending on the
age of the equipment you're talking about it might be in your best interest
to replace the equipment with high efficiency units that use PVC pipe as
venting. If not, there may be other venting options such as a power
sidewall vent. Check with other contractors and remember that it's not
always about selling new equipment, sometimes the recommendation is in your
I am in the heating and AC bussiness and I belive you "handy friend" is
wrong. Sounds like the heating contractors are steering you right.
The simplest solution to me would be perhaps two vents instead on one. The
diameters could possily be smaller and more readily hidden in a wall. 4" "B"
vent would still need a total of about 8" thick wall to conceal it. The
water heater would need less yet. Without knowing the specifics of you
furnace and water heater I am guessing though.
The best bet would be to hire a licenced contractor to deal with this for
This is not something you want to screw up. If you mess this this up it may
cost you your life and/or your home.
Your friend may indeed be handy, but his level of expertise stopped when he
advised you to convert it to 3x10!
(just for figures 9" @ .1 wc = 310 cfm, 3x10 @ .1 wc = 95 cfm, no where's
close to being the same!)
You need to find a competent contractor that you trust to not only make sure
it's up to code, but to insure your safety.
Insurance won't do any good when they find out the home owner installed
venting for their furnace that is not approved!
I can see it now, the insurance company: "Gee, your house burned down
because the furnace vent you just installed was not approved? Now you want
us to pay to build a new house? LOL!!"
Your 'handy' friend is completely, and dangerously, wrong. But no one is
explaining to you what he had in mind.
IF, and I mean IF, this was a hot air duct, the ones that distribute the
furnace's warm air to the registers in the rooms, you could indeed convert a
round duct into a rectangular wall stack (but not a small 3 x 10). But that is
NOT what you are dealing with.
You are proposing to move the main vent of the chimney and the hot water
heater. This contains very hot combustion products loaded with carbon monoxide.
This MUST be ducted through a special, double walled vent pipe called a "B"
vent. That is what the pipe in question is.
B vents have many requirements and restrictions to insure a safe installation.
A heating contractor is needed for this job, and it may prove very difficult to
relocate. You will more than likely NOT be able to reduce the size of the vent,
so the alternatives are to relocate it, build around it again, or get a new
furnace and water heater with direct, sidewall venting.
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