Fireplace dampers have traditionally been constructed of metal and installed just above the firebox. While these “throat dampers” can provide years of service, there’s a lot they don’t do well. For one, when closed, the damper seal is simply metal against metal, which isn’t airtight. This would explain why, even when your damper is closed, you feel cold or hot air (depending on the season) coming in from outside. Secondly, because they’re right in the heat of the fire, dampers can get covered in creosote and soot and end up damaged or stuck in place. But what’s the alternative?