Wood-Fired Range Cookers
How long will a wood-fired cooker burn on a full load of logs?
Burn times vary considerably depending on the species of wood, its moisture content, and how much heat you are drawing from the cooker. As a guide, well-seasoned hardwood in a full firebox will typically provide several hours of sustained heat.
Hardwood (oak, ash, beech, hornbeam) burns more slowly and produces more sustained heat than softwood. Dry wood – below 20% moisture content – burns significantly longer and cleaner than wood that has not been properly seasoned.
Will a wood-fired cooker burn reliably overnight?
Overnight operation is possible under the right conditions, but wood is a naturally variable fuel, and results depend on wood quality and heat demand. Customers should not expect wood to behave in the same predictable way as oil or pellet fuel.
For households wanting the security of a cooker that reliably holds heat overnight, the wood/electric hybrid model provides the option of electric backup – giving you the character of a wood fire during the day and peace of mind at night.
What type of wood should I burn?
Hardwoods are best – oak, ash, beech and hornbeam all burn slowly and produce sustained, even heat. Avoid burning softwood such as pine as a primary fuel; it burns faster, produces more resin and deposits more residue in the flue.
The single most important factor is dryness. Wood should have a moisture content below 20%, which you can check with an inexpensive moisture meter available from most hardware stores.
Well-seasoned logs (dried for at least 18–24 months) or kiln-dried logs (available from most wood fuel suppliers) are both suitable. Ready-to-burn certified logs meet the same standard.
How much wood will I need each year?
Fuel consumption varies according to how long the cooker is running each day, the insulation of the property and how much room heating you are drawing from the cooker. As a rough guide, many households use around three cubic metres of seasoned hardwood per year.
A cubic metre of dry hardwood logs is a useful unit to price – it is widely available from suppliers and gives a straightforward basis for comparing fuel costs.
Should logs be seasoned before use, and how can I tell?
Yes – seasoning (drying) is essential. Unseasoned wood has a high water content, which means much of the energy from combustion is used to drive off moisture rather than producing useful heat. It also produces significantly more smoke, tar and flue deposits.
Properly seasoned hardwood should have a moisture content below 20%. An inexpensive moisture meter will tell you instantly. Visually, seasoned logs tend to show cracks at the ends and feel noticeably lighter than freshly cut wood.
Kiln-dried logs are a convenient alternative and are immediately ready to burn.
Is wood a carbon-neutral fuel?
Wood is widely regarded as a low-carbon renewable fuel when sourced responsibly. When wood burns, it releases the carbon dioxide the tree absorbed during its lifetime – making it part of the natural carbon cycle rather than adding fossil carbon to the atmosphere.
The carbon neutrality of wood depends on sustainable sourcing – where trees felled for fuel are replaced with new growth. Certified wood fuel from sustainably managed forestry (such as FSC or PEFC certified suppliers) provides the strongest environmental credentials.
Do I need a chimney for a wood-fired Thornhill?
Yes. A lined chimney is required for the wood-fired model. A HETAS-registered installer will assess your chimney and specify the correct liner.
Most chimneys in properties built before 1967 will require a stainless-steel flexible liner. Properties built after that date were required by regulation to have a lined flue, though an inspection is still advisable.
If there is no existing chimney, a twin-wall insulated external flue can be installed – your installer can advise on the most appropriate arrangement for your property.
