You enjoy sitting by a comfy fire on cold winter days and nights... But you’re worried about the polluting effects of all that smoke. Did you know that choosing the right type of wood to burn can make a difference?
Help curb pollution
During episodes of winter smog, the finger of blame is often pointed at residential wood heating: indeed, smoke from burning wood contains all manner of contaminants, including fine particles, which are the major component of smog. Stricter standards have helped to considerably reduce fine-particle emissions: today’s high-efficiency appliances emit only a tenth as much as older models do. To learn more, read our clarifications at the end of this article, as well as the Tips & Tricks instalment Heating with wood.
If your wood stove or fireplace meets those tighter standards, that’s good news. But to ensure that your appliance works properly and helps reduce pollution as it’s designed to do, you must also:
- choose species of wood known for their combustion efficiency;
- use dry, clean wood; and
- properly control combustion.
Select the right tree species
Hard, dense woods like maple and oak have high heat value. They burn for a long time and the coal bed lasts longer, allowing stoves and fireplaces to operate at their full efficiency. These species include:
Heat value per cord (millions of BTU)
|Hickory, red oak||28|
|Beach, yellow birch||25|
|Ash (local use only) red elm||24|
Some types of wood that aren’t quite as energy-efficient still make excellent fuel in the spring and fall. Their heat is easier to control, and they won’t overheat your home. These species include:
Heat value per cord (millions of BTU)
|Red maple, white birch||23|
Softwood species like pine and spruce are to be avoided. Their heating value is low, and burning them leaves a great deal of creosote deposits in the chimney.
Use dry wood
No wood used for heating should have a moisture content higher than 20%. This is an essential condition. If you burn wood wetter than that in a high-efficiency appliance, the unit will not achieve the low fine-particle emissions combustion that it is designed to. The moisture in the wood makes it slow to burn, and produces more smoke and creosote; the ceramic-glass door will also become stained.
To properly dry wood, it must be seasoned; i.e., cut and split during the winter (when there is no sap) and properly stored for the entire summer. Proper storage means wood stacked outdoors, protected from the rain, and in separated rows, spaced sufficiently far apart to allow good air flow. No logs must touch the ground.
To ensure good combustion, logs should not exceed 15 cm (6 in.) in diameter, and should be between 35 and 40 cm (14 to 16 in.) long.
It’s better to keep only small quantities of wood inside the house, to keep the humidity from getting too high. You should also check with your insurer: your policy may contain restrictions on storing wood indoors. Also, be sure not to keep a large amount of firewood on a balcony: a short cord (also called a stove cord, which is a third of a cord, or about 4 ft x 8 ft x 14 to 16 in.), weighs about 680 kg (1,500 lb).
How can you tell if wood is dried enough to burn? Properly seasoned logs have more cracks in them, weigh less and are darker in colour, and when you bang two of them together, it should make a hollow sound.
You can also use densified-wood logs in a high-efficiency appliance. Because of their superior heat value, though, care must be taken not to overload the appliance (read our Tips & Tricks instalment “Eco” logs: make sure things don’t overheat! for detailed information).
Maintain the appliance and chimney
Achieving clean combustion also requires regular maintenance of both the stove/fireplace and the chimney. Plus, having an annual maintenance contract with a certified professional will greatly reduce the risk of a chimney fire due to creosote buildup in the flue.
Clarifications about wood-burning appliances
CSA B415 or EPA certified appliances
Since 2009, the manufacture, sale and distribution of wood-burning appliances that are not compliant with the environmental standards of the Standards Council of Canada (CSA B415) or the U.S. Environmental Protection Agency (EPA) have been forbidden in Quebec. On this subject, read the Regulation Respecting Wood-Burning Appliances, developed by the Ministry of Sustainable Development, Environment, and Action against Climate Change.
Montreal: a special case
The city of Montreal initially banned the use of solid-fuel-burning appliances. It has since reviewed its position and announced its intention to allow, as of October 1, 2018, high-efficiency appliances that emit no more than 2.5 grams of fine particles per hour, which corresponds to the future EPA “step-two limit,” due to take effect in 2020. The industry is ready ahead of time, with several wood-fired appliances that meet that standard already on the market. To learn more, read the Montreal By-law Concerning the Use of Wood-Burning Stoves and Fireplaces.