Burning wood for central heating has long been an attractive proposition in rural areas where there is a ready supply of fuel. However, traditional wood heating appliances also have a reputation for being been smoky, dirty and crude. But they don’t have to be.

In recent years a number of efficient wood burning boilers and forced air furnaces have come on to the market, presenting an opportunity for rural HVAC contractors to approach customers that are already burning wood and sell them on more comfortable and efficient heating.

New technologies and better controls help the new generation of wood burning appliances achieve higher efficiencies, longer burn cycles, excellent comfort levels and minimal emissions, while reducing the amount of wood required over the heating season and minimizing maintenance.

These units must meet the CSA B415 Standard that specifies requirements for performance testing of solid-fuel-burning appliances, including maximum emission rates. The latest edition is also expected to include wood boilers. It is similar to the U.S. EPA’s voluntary Phase 2 hydronic heater program, commonly known as the “white tag program.” They must be installed according to the CSA B365 Installation Code for Solid Fuel Burning Appliances and Equipment, along with the manufacturer’s instructions.

The key development that has made clean burning wood heating possible is secondary air or “wood gasification.” Essentially, the wood burns initially at about 550ºF in one chamber and then the gases present in the smoke burn in a second chamber at temperatures as high as 2,000ºF (1093ºC). While a typical wood stove might extract 40 to 60 percent of the heat energy in a log, wood gasification technology can take that as high as 90 percent.

In a traditional wood stove, much of the heat escapes up the chimney. A modern wood-burning appliance captures most of it, reducing stack temperatures to about 350ºF.

This efficient burning largely solves several other traditional wood heating problems such as large amounts of ash, smoke and creosote. But there’s a proviso there, notes Tony Comeau, P.Eng, technical marketer for Newmac Manufacturing in Debert, N.S. “Well seasoned wood and a well designed system is a major part of the battle.” If the wood is wet, not only will the efficiency drop off, but maintenance will increase dramatically.

As with the installation of any heating system, doing a heat loss on the home is important. In fact, it’s more critical with wood because oversizing can result in a home that’s always too hot, said Comeau. “The contractor really should have a good look at the structure and see what’s going on.”

Wood furnaces are often rated by average output rather than maximum output like a conventional furnace. It’s better to undersize slightly than oversize. The operating style of the homeowner makes a difference too. Do they put in a couple of logs at a time, regularly tending the fire, or do they load up the firebox with enough wood for the day and leave it? And different woods have different heat outputs.

While it’s getting closer, wood heating technology is never going to be “set-it-and-forget-it” like forced air gas and oil heating.

And it’s usually the homeowner/operator that maintains a wood heating device, calling in the contractor only to maintain the backup if it’s an oil or propane furnace.

The homeowner must establish a secure supply of wood by purchasing it or gathering, cutting and stacking it. They must also do their research, adds Comeau. “There are different types of wood. They have different ash content and heat output.” Fortunately, much of this information is readily available on manufacturer’s websites.

A backup source of heat is a must to prevent pipes and people from freezing when the fire goes out; in fact most insurance companies require it.

Newmac, for example, offers electric inserts in 10, 15, 20 and 25kw sizes for its wood furnaces. A 20kw unit is typical for the average sized home, but both it and the 25kw unit require a 200-watt panel. The smaller inserts are typically used where the home has a 100-watt panel and the homeowner can’t or won’t upgrade.

HVAC contractors have an enormous advantage in selling and installing wood boilers and furnaces because they understand forced air and hydronic heating along with the controls, said Ben DeBruyn, Ontario sales manager and technical trainer for ProFab Industries, Arborg, Manitoba, manufacturer of Empyre wood boilers (and a longtime HVAC contractor himself). They need a basic understanding of heating with wood, something they can get by taking a WETT training course (see sidebar).

Selling a wood heating system isn’t a lot different from selling any heating system, says DeBruyn. Contractors have to remember they “are in the comfort business, not the heating business.”

Most customers don’t need to be sold on wood heating. They are already knowledgeable. “It really is a lifestyle system,” notes Comeau. Better comfort, efficiencies, reduced maintenance and longer burn cycles are making that lifestyle desirable for more people these days.