Hello,
I have been wrestling with this question for quite some time. I have
a two story house with a concrete block chimney with clay tile liner.
I have a oil fired forced air furnace with an add on wood stove piped
into the same chimney. I have been heating my home with this set up
for close to 30 years so I am not a wood burning greenhorn. I have
never had a chimney fire or at least one that I was aware of. I keep
the chimney clean and burn only seasoned hardwood. My question is
that my chimney has about a 3 inch air space which goes up all the way
into the attic and adds alot of warm air into the attic which I think
causes ice to form at the eaves. Would I be making a big mistake to
insulate around the chimney where the chimney extends into the attic?
What about insulating around the whole chimney inside the attic? I
would guess the outer block temp gets pretty warm but not over 200
degrees F. Although, a chimney fire, if one did occur, could approach
or exceed that temp..... Or should I just leave well enough alone and
put up with the ice buildup at the eaves?

Thanks,
Steve

ps I have about a foot of fiberglass batt insulation in the attic
floor.