Well, my SF-260 is a hand fired boiler. I have a 150 year old farmhouse with blown in insulation in the roof and walls and modern multipane windows. Total of about 2200 sqft. stack temp, pre baro, runs about 300. Where I do lose heat is about half of the house is over crawlspace. The floors are insulated but if the floor is cold, the people are cold. for whatever reason, when it gets super cold, it takes a lot of coal to keep the water temp up. Once we lit the wood stove, we were fine. Now that I think about it, for the faster burning days, I should switch back to wood in the boiler too.