Heating with a wood stove

Wood is one of the most common ways to heat an off-grid or rural home. Modern stoves are very different from old ones: they burn cleaner, make less ash and use less wood for the same heat.

Certified stoves

EPA has set smoke limits for new wood stoves since 1988. The current limit, in force since 15 May 2020, is 2.0 grams of smoke per hour. Some newer models certify between 1 and 4 g/h. An old, uncertified stove puts out 15 to 30 g/h. When comparing models, a lower g/h rating means a cleaner, more efficient stove.

To check whether a stove is certified, look for the metal label on the back, or look the model up in EPA’s database of certified wood heaters.

Two designs

• Non-catalytic stoves get a clean burn from an insulated firebox, a large baffle that makes the hot gases travel further, and preheated air fed in above the fire. Most stoves sold are this type. The baffle and some internal parts wear out and need replacing.
• Catalytic stoves pass the smoke through a coated ceramic honeycomb where it burns. They give long, even heat, but are a bit more work to run. The catalyst wears out and needs replacing: it can last more than six seasons if used well, but over-firing or burning trash and treated wood ruins it.

Sizing

• Small stoves suit one room or a seasonal cabin, or “zone heating” one part of a bigger house.
• Medium stoves suit small houses and well-insulated medium houses.
• Large stoves suit big open-plan houses, or older, leaky houses in cold climates.

A tight, well-insulated house needs a much smaller stove. Take a floor plan to an experienced hearth retailer.

Burning well

• Split wood small, so it dries faster and burns more completely.
• Start with natural fire-starters and small dry kindling, then add bigger pieces once it’s burning well. Leave gaps between pieces for air.
• Go outside and look at the chimney. Smoke usually means the fire needs more air.
• Keep about an inch of ash in the firebox to hold a hot coal bed for restarts.
• Take ashes out only once they’re cool, and store them in a metal container away from the house.
• Never burn garbage, plastic or treated wood.

For a Leafhouse project

Wood heat pairs well with passive solar design: the sun covers the clear days and the stove covers the rest. Plan the chimney route and a dry woodshed into the design from the start, and ask the building department whether the stove installation needs its own permit.