With our old woodfurnace before insulating and airsealing, when it was in the 30's we would load about half load for night which was around 3+ cu.ft. The house would get too hot overnight and halfway through the night the furnace would burn out. In the morning we would wake to a cold house and furnace. Late winter early spring this year, we airseasled our attic and added 12" of cellulose on top of the 3" that was there. With our new furnace, last night it was in the low 40's with a frost warning I added 1/2 load 1.5 cu ft of thinner Slabwood pieces, which would have been kindling for the old furnace. Closed the damper at 9:30pm. I woke up this morning at 6:30am to a 73 degree house, mid 30's outside. The kicker is the woodfurnace appeared out and hadn't ran for a couple of hours. I stirred the ashes with a poker and up came many live coals. I threw some more slabs on the coals and the fire took off. Its a huge difference. If I was able to get Slabwood cheap I'll consider it now. With the house holding heat longer and a more efficient furnace our wood usage has dropped quite a bit. I couldnt be any happier! It goes to show that a large old home doesn't have to be an energy hog. Of course 30's isn't cold by any means, but things were alot different before the energy upgrades. We don't have the swings in temps and we don't feel drafts. There's still some room for improvement so things will only get better.