Feels like a rookie mistake, but I thought I'd share my oversight for anyone that might benefit. Started using a Vermont casting Merrimack insert as my primary source of heat three seasons ago. House is fairly new, and about 3000 sqft, so this unit is able to heat the whole place pretty well in southern nh. Since playing with my rebuilt firelight 12 A few weeks ago, I began to recognized the impact small changes in gasket condition can make. This prompted me yesterday to check out the Merrimack, and I found that on the bottom of the right door the 3/8" gasket had never even been compressed against the stove when the door was closed. The dollar bill test showed no resistance,so I decided to redo the doors. The manual for the insert tells you to stack gaskets if needed to take care of loose points, so I ended up having to do that in a 10" section. End result is a completely different stove that I now have to learn how to burn once again. Though it always treated me well, the air control lever never seemed really effective, a completely different case now. With tight doors the fire appears to burn just as slow as my cat stove, and slight adjustments in air position are instantly noticed. I never pay anyone to do anything for the most part, but I hired a reputable local stove company to do the insert and chimney liner install due to fear of messing up something so potentially dangerous. I assumed that everything was done correctly and checked, but I'm depressed thinking about how much extra wood I've used due to a poorly fitting door. Next time your stove is cool, I highly recommend checking the gaskets. Mine were still in great shape, but weren't doing anything.