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NC State Extension


A fireplace can waste more heat than it creates

A charming old fireplace may seem warm and cheery, but when there’s no fire burning the fire- place can cause substantial heat loss from your home. Even if you close the fireplace damper and it leaks just a little, a lot of warm air from your home will be sucked up the chimney and be replaced by cold air leaking into the house.

If you never use the fireplace, put a plug in the flue of the chimney to reduce heat loss. Seal the plug to the chimney with caulk, and be sure to tell anyone who may want to start a fire that the chimney is plugged. You also can secure the damper in place and caulk around it to eliminate air leaks.

If you use the fireplace, follow these tips:

  • Everyyear,havethefireplaceandchimneyinspectedandcleanedbyacertifiedchimney sweep. Creosote buildup in the chimney can ignite, causing a fire that easily can spread to the walls or roof.
  • Check the seal of the flue damper. Close the flue, light a small piece of paper (or an incense stick) and watch the smoke. If the smoke goes up the flue, there’s an air leak. Seal around the damper assembly with refractory cement, but don’t seal the damper closed. If the damper has warped from high heat, have a sheet metal shop fabricate a new one or install a metal chimney top damper.
  • Inflate a chimney balloon in the chimney above the damper when you’re not using the fire- place. It inflates like an air mattress, expanding to seal air leaks; if you forget to remove it before starting a fire, it will react to the heat and quickly deflate.
  • Install tight-fitting glass doors. Controlling the airflow in your fireplace improves combustion efficiency by 10 to 20 percent and reduces air leaks up the chimney.
  • Add a heat-circulating grate with a built-in fan to blow heated air into the room; some models have a thermostat to reduce fan speed as the fire burns down. Be sure to buy a unit designed specifically for your style of fireplace.
  • Makeatight-fittingplugforthefireplaceopeningfromrigidboardinsulationbackedby plywood with pipe insulation around the edge. Finish it to match the room’s decor, and insert it whenever the fireplace is not in use. 

Source: Iowa Energy Center