Do glass doors on a fireplace reduce the amount of warm air that get wasted up chimney?
Fireplace glass doors reduce the amount of already heated interior air that the fireplace has access to. So it does slow down the inside heated air from being cast up the chimney with the fires combustion heat, but glass doors do not stop this heat waste completely. Fireplace glass doors also inhibit the only usable heat the a fireplace produces (radiant heat) from comming into the living area. Standard open fireplaces and fireplaces with glass doors are notoriously inefficient at heating the home. According to the US Department of Energy using a fireplace in the winter will actually make your heating bill go up by 10% on average.
