The winter block guide

How to light a hot, clean fire

Norwegian energy researchers Øyvind Skreiberg and Morten Seljeskog have been researching wood burning for 25 years. They say, if you get a burn right, you can reduce emissions from a fire by 50-80% compared to an inefficient burn.

Aim for the perfect flame

Perfect flames are the best indicator of optimal combustion. They’re light coloured with blue tones close to the wood and shouldn’t be filling the entire firebox. Dancing orange-yellow flames that fill the firebox are a sign of too much air. Small, weak flames topped with visible smoke mean too little air.

THEIR TIPS

■ IF YOU have a woodburner from before 1998, it’s best to replace it. Modern designs are vastly superior in terms of energy efficiency and emissions as they use a more sophisticated staged air combustion process.

■ A NEW woodburner will come with instructions on how to get the cleanest burning fire. It’s important to read them as you manage their airflow quite differently compared to old models. Instructions will include how much wood to use, and how to stack it in the firebox.

■ OPEN a window to get airflow through your home before lighting a fire. Switch off any vents such as ovenhoods, and keep the door of the burner open for at least 20 minutes after you light a fire so it can more easily consume the large amounts of air it needs.

■ DON’T use newspaper to start a fire. Instead, it’s best to use dry woodchips, bark, or firelighters.

■ ONLY use small, dry pieces of firewood, not wet or large logs, or rubbish. Their research shows the perfect piece of firewood is 27cm long, and 2x5cm thick.

■ WOOD that’s too wet expends most of its energy turning the moisture into steam, not heat. Dry wood will ‘ring’ and sound hollow if you hit two pieces together, compared to the dull ‘dump’ sound of two wet pieces. If you’re not sure, you can buy a simple moisture meter for wood from hardware stores for about $30-$40.

■ TO GET the hottest fire, only fill the firebox to about 25% of its capacity. Once it’s at its hottest, it’s best to regularly add small pieces of wood and lay them horizontally to get maximum heat and low emissions.

■ DON’T let firewood touch the walls or the glass of the firebox. This cools the flames, which creates more soot and less heat.