Please excuse me for not fully searching before posting (which I will do), but maybe someone knows this stuff off the top of their head. I have an insert in a zero clearance fireplace that is vented by a liner inside the original sl300 fireplace flue. If I'm not mistaken, the SL300 is air cooled, but I'm not sure where it gets the cooling air from; I'm not even sure how it works. Early on, I stuffed up the air vent on the outside of the house because I thought it was for outside combustion air, which the insert does seem to need, from the way it's performed, and the general area in front of the tove felt cold. I wonder though, if cooling air for the SL300 came from there too? I recently looked at a big Quad zero clearance epa fireplace, and I believe they told me it used a dedicated air duct from the outside for cooling air. I've only been on the roof a couple of times (metal roof, height, etc), so I don't remember what it looks like up there. Thanks for any insight. I'll be doing some searches as well.