Question: I have a question I hope you can answer. Since purchasing my home with a wood fireplace, I have learned a great deal about the efficiency (of lack thereof) of my wonderful wood burning fireplace. Your Q&A section has been impressively helpful in answering almost all my questions. I have come to the conclusion that if I want to reduce or eliminate heat loss out of the home, I need to install an outside fresh air vent and air sealed glass doors. My one nagging question is this though. I understand that when the fire is low, or burning out, the use of the sealed glass doors and outside fresh air vent will hopefully eliminate warm air from the home escaping out the chimney. But my question is this: When the fire is nice and hot, I want to open the glass doors to allow the radiant heat out. In doing so, will the radiant heat add, equal or be less than the warm air the fire is burning and sending up the chimney? Basically, will the fire still pull more heat from the home than it provides? I understand that I definitely am losing heat when the fire is just getting started, and when it is burning out. I would keep the glass doors closed at these times. But to prevent a negative heating impact on the home, is it okay to open the glass doors and allow the radiant heat out, or am I just burning air in the home and sucking cold air in through draft spots, thereby eliminating the effects of the radiant heat being given off? Answer: You have the right idea. If you open the glass doors during the hottest part of the fire, the gain into the house will more than offset the loss up the chimney....at least in most cases. Your heat output can be improved by use of the proper grate and by the possible partial closing of the damper if you have too strong of a draft.So - yes, open the glass doors when the fire is hot and especially when the entire fire is a mass of glowing coals. This way you will get the full benefit of the radiant heat.