Fireplace insert insulation

[Jhrobert]

I recently purchased a used Osburn 1600 fireplace insert. The previous owner told me that there was pink insulation all around the stove when he had it removed. I have installed the insert without any insulation and was wondering if I should have insulated it inside my fireplace? Should the pipe between my newly made damper plate and the stove be insulated? If so, with what type of insulation? I want to make sure that this setup has no drafting around the stove. So far so good as I have to leave a window partially opened when I run the stove due to lack of air coming into my house. My chimney has three flues in it. With all the windows closed my other fireplace pulls smoke back down it and into the house. I have sealed off the damper plate with silicone. I still get a very minimal amount of smoke if the windows are all closed. It appears that the damper housing itself was not put in air tight in the cement. Today I sealed that off with silicone. This fireplace is not used so sealing it off is not a problem. Should I cut a vent somewhere in an outside wall? TIA Jim