The flue that lets smoke and heat out will sometimes have a damper. Dampers swing freely and are not an airtight situation when closed. When you don't have a fire the cold outside air is coming into the firebox and you have radiant cold. The flue taking out the exhaust gas or the smoke and heat out to the roof line can be different diameters. You need to measure the diameter of the flue and make sure the Flue-zee can attach and close off the hole. Our Flue-zee Flue Cover is easy to install and remove when you have a fire and has a safety red alert ring. See position #1 inside firebox closing off flue.
The Convective Heat vents that you see in the diagram circulates warm air when you have a fire. When you have no fire the cold air in this vent begins to circulate in the opposite direction and throws cold air out of the bottom of the vent. Blocking this cold air at the bottom vent and the top vent with our Magnetic Fireplace Vent Covers will stop this cold air. Our cover will slide up under a small upper awning if you choose to cover the top vent. Stopping this cold convection will give you a lot of relief. You must remove the covers when you have a fire to get warm air circulating. If your vents protrude (looking more like venetian blinds) and are not flat to hold the magnets flat around the edge, or if you have a screen over them, our magnetic covers will not work. See position of #2 of vent openings to Convection Air Intake/Convection Heat.