Our fireplce gas insert always has this cold draft coming out of it when
not in use. The flue damper was removed when installed. The insert is
feed by two three inch pipes. I have been told to stuff some insulation
up the flue to seal it up. Roxul safe and sound was mentioned. Itd seems
to be very fire resistant.

Is this a normal thing to do? I was told the installers should have done it.