Also, Maybe there is a kit for your fireplace to make it vent outside and get its combustion air from outside. If available, this should only be purchased from the factory authorized dealer. Usually these units are purpose built and cannot be modified. If you are lucky you can. Maybe they will trade in the unit for a direct vent. Myself, I don't like the idea of non-venting units. Just think what is probably happening where you can't see, like the condensation inside your walls or in your attic. Unless your vapor barrier is PERFECT, which is pretty much never the case in any house, you will end up having water, mildew and rot inside your walls and insulation. Not a good thing.