Here in Ontario the first upgrade the safety people make us do on a wood burning appliance is put a steel liner into those old clay tile brick chimneys. The outside stoves are great but not nearly as efficient as an airtite stove. We have a smallish airtite to avoid using the electric furnace. The house is 1600sq ft and we burn about 2 1/2 bush cords per winter, heating the basement as well. Yesterday I started the furnace for the first time this year, but it has been hitting -32C at night with -20c during the day.