Not all firewood burns the same. If you're heating with logs, the amount of moisture in the wood has a direct impact on heat output, burn quality, smoke levels and stove performance.
There’s often confusion between kiln dried and seasoned logs — they’re both dry, right? Not quite. Seasoned logs are air-dried naturally, while kiln dried logs are dried in a controlled chamber using heat and airflow. This ensures consistent moisture content, usually around 15 to 18 percent — dry enough to meet the UK’s “Ready to Burn” standard.
But we like to hold ourselves to higher standards, so we choose to dry our logs even further, to below 15 percent. That means better performance, cleaner burns, and more heat in every log.
What is a seasoned log?
Seasoned logs are typically dried outdoors for 6 to 24 months, depending on wood type and climate. If well-stored, they might reach 20 to 25 percent moisture content. But in many cases — especially with poor storage or faster drying — seasoned logs are still holding 25 to 40 percent moisture.
According to data from Heritage Products and Fitzpatrick Fuels, logs at this moisture level produce significantly less heat, and generate more smoke and residue when burned.
What is a kiln dried log?
Kiln dried logs are dried in a controlled chamber using heat and airflow. This ensures consistent moisture content. Logs with less than 20 percent moisture meet the UK’s “Ready to Burn” standard — but those closer to 15 percent or lower like ourselves offer far better performance.
Heat output comparison
The difference in energy output is huge. According to data confirmed by Heritage Products:
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Kiln dried logs (7–15% moisture) produce 4,500 to 5,000 kilowatt-hours (kWh) per tonne
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Seasoned logs (25–40% moisture) produce just 2,300 to 3,500 kWh per tonne
This means kiln dried logs can produce up to twice the heat of seasoned logs, depending on moisture level. The more moisture in a log, the more energy is wasted evaporating water — not heating your home.
How many logs will you burn?
To heat a typical UK home with a 5 kW stove used for 3 hours per day from October to February, the seasonal wood requirement looks like this:
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Kiln dried logs: 3 to 4 cubic metres (loose volume)
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Seasoned logs: 6 to 8 cubic metres (loose volume)
This is based on consumption estimates from Heritage Products and Fitzpatrick Fuels, and assumes consistent wood species and quality. In short: you’ll need about twice as much seasoned wood to generate the same warmth.
That’s twice as much stacking, storing, and spending.
Other drawbacks of seasoned logs
Seasoned logs burn cooler, take longer to light, and generate more smoke. More moisture also means more soot, which can lead to faster flue blockage, increased maintenance costs, and a higher risk of chimney fires.
For DEFRA-approved stoves or homes in smoke control zones, burning seasoned logs can also create issues with air quality compliance.
Seasoned logs are also inconsistent. Because they rely on ambient drying conditions, batches can vary in dryness — even within the same delivery.
Why kiln dried is the better choice
With kiln dried logs, you know exactly what you’re getting. They light easily, burn hotter, and produce less smoke. Because there’s less moisture, you get more energy from every log and less wasted fuel.
You’ll also need less storage space and fewer deliveries through the winter, which is ideal for small log stores or frequent users.
For homes relying on wood as a primary or regular heat source — and for businesses such as spas, B&Bs, restaurants or holiday lets — kiln dried logs are the most reliable option.
If you want less smoke, more heat, and cleaner-burning firewood, kiln dried logs are the smart choice.