Efficient, Convenient Wood Heating (CMHC)

Feb 2, 2016


More than one million Canadian families heat their homes at least partly with wood. For these households wood is an important energy source, one that involves their active participation. Having control over the fuel supply offers security from electrical power interruptions and shelter from rising conventional energy costs.

Considering the many advantages for those who live at the urban fringe and beyond, wood heating is worth doing right. “Done right” means making sure the wood heating system is installed exactly to safety codes, preparing good quality firewood and operating the system using techniques that will produce the best efficiency and effectiveness.

System design and safety

The chimney is a critical component of a wood-heating system. It is much more than a simple exhaust pipe. It is the engine that drives the system by producing the pressure difference, or draft, that draws in combustion air and expels exhaust outdoors.

To work properly, a chimney must be installed up through the warm space of a house, rather than through a wall and up the outside.

The venting system—the flue pipe and chimney—should be as straight as possible. The best performing system has the flue pipe running straight up from the flue collar of the wood-burning appliance to the base of a chimney that runs straight up through the roof.

“Advanced-technology wood-burning appliances,” which have been available since 1990, are about one-third more efficient than older conventional units, such as 1970s and 80s “airtight” stoves. They are identified by their Environmental Protection Agency (EPA) certification or compliance with CSA standard B415 of the Canadian Standards Association (CSA) for low smoke emissions. If you are planning a new wood-heating system or thinking of replacing your older stove, take advantage of the new technologies and save yourself time, money and work.

Your best resource for reliable woodheating information and service is a WETT-certified retailer, installer or chimney sweep. WETT stands for the Wood Energy Technical Training program, Canada’s national training system for wood-heating professionals. You can find the WETT-certified professionals near you by visiting www.wettinc.ca or by calling WETT at 1 888-358-9388. In Quebec visit l’Association des professionnels du chauffage (APC) at www.poelesfoyers.ca or call (514) 270-4944.

Buying and preparing firewood

Good quality firewood is essential for efficient and convenient wood heating. Good firewood is the right size for the appliance firebox and is properly seasoned.

While hardwoods like oak and maple are fine for very cold winter weather, softer woods like birch and poplar make better fuel for milder spring and fall weather.

As much as half the weight of freshly cut logs can be water. This water content must be reduced to 15 to 20 per cent before the wood can burn efficiently. How you process and store the wood is critical to achieving this moisture reduction goal.

Cut the logs into pieces that are at least 75 mm (3 in.) shorter than the firebox. For convenient handling and fire management in most woodburning appliances, firewood pieces should not exceed 40 cm (16 in.) in length. Piece lengths as short as 30 cm (12 in.) can be better for small heaters. Just because your stove’s firebox can handle 50 cm (20 in.) logs does not mean that logs that long are needed or even desirable.

Split the wood into a variety of sizes for convenient fire building and maintenance. Large pieces are fine for large fires in cold weather but smaller pieces are needed in mild weather and for fast ignition of new fires or fires rekindled from coals. Commercial firewood is generally not split small enough. For most appliances, split the wood in a range of 8 to 15 cm (3 to 6 in.) measured at the largest cross-sectional dimension. Although this means more splitting and more pieces to handle, each piece is easier to lift and more importantly, fire management will be much more convenient all winter long.

Storing wood

In the early spring, wood should be cut to the right length, split to a variety of sizes and stacked off the ground on rails in an open area exposed to sun and wind. Prepared this way, the firewood will be ready for burning that fall. The tops of the stacks should be covered to prevent rain from soaking down through them. Prime time for firewood seasoning is the very hot days in July and August when the sun beats down, warming each piece of wood while gentle summer breezes rinse away the moisture driven out of the wood. If possible, don’t pile wood in a shady area and never stack green wood in a woodshed because it will not dry properly in time for the heating season.

In the fall, ideally after a few sunny days, the wood is moved to its winter storage location. Winter storage should be close to, but not inside, the house and fully sheltered from rain and snow so the wood stays dry

How to start a fire with little or no smoke

A kindling fire that collapses into a smouldering mess is frustrating and also embarrassing if someone is watching. By following the suggestions offered in this About Your House, you can avoid future frustration by building kindling fires that ignite quickly and burn reliably.

The kindling fire should quickly heat up the chimney to create strong draft and heat the brick and steel of the firebox to create a good environment for stable combustion. The type and form of kindling materials affect the behaviour of the fire. The edges of split firewood heat up and ignite first, so the more edges there are close together in the kindling fire, the faster it will ignite.

Kindling pieces need to be finely split to produce many edges where the fire will first catch. The lower density and usually higher oil content of softwoods like cedar, pine and spruce make them better for kindling because they ignite more readily than hardwoods. The drier and more finely split the kindling, the faster and more reliably will the fire ignite and burn.

In preparing to build a wood fire, remove excess ash from the firebox. Ash should never be allowed to build up to more than five cm (2 in.) in thickness. Next, locate where the main supply of combustion air enters the firebox—that’s where you want the fire to first ignite. Open the air control fully.

There are two popular strategies for building kindling fires that don’t collapse and smother themselves: the two parallel logs technique and the top-down fire technique.

Source: Canada Mortage and Housing Corporation

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