Insulating around Vent Free Propane Fireplace

I have a problem with cold air blowing in through the top vent of my fireplace in the winter. I beleive it may be due to lack of insulation behind it.

Could I just cut a hole from the outside and fill in behind the fireplace with blow in insulation or would that be a fire hazard?

Or is there a better solution?

Thanks,
Scott

 

I'm sorry no one has replied to your question.

I'm confused to your situation. You title states it's a vent free fireplace but you state cold air is blowing down the top vent.

It sounds as though you have a log set in a brick and morter fireplace? Is this correct? If so, you need to make sure your logset is approved for vent free use and local code allows use of vent free logs. If the answer to both questions is yes. You can keep the damper closed.

I would be leary of blowing any sort of insulation into a chimney if that's what you're proposing to do.