Extra insulation for a one inch \"A\" vent oil chimney

Mike Lampkin_2

I have an "A" vent oil chimney (one-inch wall thickness)
that has a total overall height of 36 feet and goes up
through the center of the house. The chimney is condensing
at the top because of the low flue gas temperature (It is
only 310 degrees F) at the base tee. I would like to wrap
extra insulation around the chimney, up in the attic space
to give it at least a R6 value, since the attic space is 12
feet high and is not insulated. If I can make the chimney
warmer, I should no longer have a condensation issue. Does
anybody see a problem with wrapping foil-face fiberglass
insulation tight around the chimney after taping all of the
joints with a metal tape? The chimney runs through open
attic space and up through the roof. Thanks in advance for
the help.

ed wallace

wrapping vent pipe

i have reservations about that i believe the manufacturer calls for at least a 1 in air space around the vent pipe

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Mike Lampkin_2

Air space

Hi Ed,
That's what I have been trying to find out from the chimney
manufacturers. If the chimney is in an open space and is
not in contact with combustibles, why would there have to be an air space? The chimney is rated for 1000 degrees F
and will never get over 330 degrees F, so it is not like
the chimney is going to over-heat. With an air space, would
you not have less R-value than with the chimney being wrapped tight? Thanks...

Mike Lampkin_2

Are there any chimney representatives on the \"Wall\"....

....that can help me with the air space question? Thanks

Bob Harper

insulation in stated clearances

You cannot pack insulation in stated clearances. These are air spaces. Has to do with pyrolysis of adjoining combustibles from radiant heat. Even if no combustibles nearby, you're voiding the warranty. With mfd products, always follow mfrs instructions or you're on your own.

Condensation in Class A chimney is probably due to oversizing, esp. at 36 feet on interior of house. Remember, you have to heat up all that mass of chimney to maintain a stable draft. Also, what's the sulfur content of your oil? High sulfur= condensing at higher temps. What's the firing rate in GHP? You already have a very low stack temp.
Bob in Philly

Mike Lampkin_2

Thanks Bob...

The chimney in question is not oversized. It has an internal
diameter of 5 inches. The boiler is a Vitola VB2-40, which
has a 170,000 btu input and a one gallon nozzle. The output
temperature of the Vitola at the breech is only 330 degrees
F, which is the reason for the low stack temperature. This
is why I'm trying to get the chimney better insulated. If
I can get the chimney to at least R6, I can have a lower
stack temperature at the base tee of the chimney. None of
the chimney manufacturers, that I know of, make a 5 inch
"A" vent chimney with 2 inch thick walls. If I build an
insulated box around the chimney with the appropriate air
space between the chimney and the box, will this solve my
problem? Thanks again...