ARC E-Newsletter 3/28/25: Wood Heating - Heating Design Load
Aprovecho Research Center
Burning wood slowly (and cleanly) can be a big part of the challenge when improving heating stoves. Air tight, insulated houses do not need big fires to stay warm. If the fire is too large, the house gets hot and folks are opening windows!
What firepower is needed to keep a house warm but not overheated?
“If you build a small, tight, well-insulated home — in other words, a green home — it won’t need much heat. Since typical residential furnaces and boilers are rated at 40,000 to 80,000 BTUH, they are seriously oversized for a super-insulated home, which may have a heating design load as low as 10,000 to 15,000 BTUH.” www.greenbuildingadvisor.com/article/heating-a-tight-well-insulated-house
15 thousand BTUs per hour is equal to about 4.4 kilowatts. (Burning ~2 pounds of dry wood per hour in a stove with a good heat exchanger.)
The required firepower of the heating stove is dependent on the losses from your house. Old-fashioned houses can require big fires to replace constantly lost heat.
The Green Building Advisor says that it is most cost effective to reduce the air leaks first and then increase the amount of insulation in a home.
Matching needed firepower to your heating design load should factor into your decision of what stove to buy. It is not difficult to do an energy audit of your home.
www.energy.gov/energysaver/home-energy-assessments
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