A wood burning furnace can be bought at Home Depot, Charmaster, Central Boiler and WoodMaster. Home Depot offers online shopping and pickup at local stores. Add-on units are designed to supplement existing systems.
Wood-fired furnaces can link to existing ducting to supplement a furnace already in place. Several outdoor and indoor models exist and offer different advantages. Some units feature blowers that can run in conjunction with or independent of the existing circulation systems. Outdoor units are subject to extreme temperatures and the elements, but are best for heating multiple buildings. Many come insulated with outdoor lights and efficient burn times.
Wood-fired furnace technology has increased the reliability and cleanliness of the units. In addition to heating the house, many of the furnaces can be plumbed to heat hot water for cooking and bathing, including the model available at WoodMasters.
Fireboxes can be either round or square. A round firebox has no seams and is less likely to crack. The blowers and the motors used to circulate the air are equally ass important as the construction of the firebox. Make sure the ducting can be fitted with a pre-filter so nothing enters existing ducting. In addition to a electric thermostat, a manual damper can help to fine-tune the unit.