fasteddie is right the only way to go is air tight.. i have a 3200sq foot house with a free standing
quadra-fire stove in my den and a quadra-fire insert in my bar room i can heat the house to 70 and keep it there all winter long. just load up and burn for about 7 hrs,The insert runs 24 7 from Nov. to the end of march. I burn about 6 to 8 cords a year,its alot of work, but i only use 12 gallons of fuel oil a week. I love it.