This past weekend I was up in the attic getting ready to lay down some
insulation when I noticed that there was a pretty big gap between the
chimney and the adjoining wall running pretty much the whole lenght of
the chimney. I wasn't able to get close enough to measure it, but I'd
say it's close to an inch pretty much the whole way.

Is this something I can seal with a can of the spray foam sealant or do
I need something else?

TIA,
tmo