What is the difference?
Moisture content is what separates good firewood from frustrating firewood. It directly affects how easily your fire lights, how much heat you get, and how quickly your stove glass turns pitch black.
While suppliers widely sell both kiln dried and air dried logs across Ireland, the two types perform very differently. Before you place your next order, it is well worth knowing exactly what you are buying.
What is air dried firewood?
Air dried firewood is cut, split, and left to dry outdoors, under cover or in warehouses for several months. In good conditions, hardwood can season down to around 20% - 30% moisture in 12 to 18 months. The challenge is that results vary a lot depending on how and where it was dried.
The outside of a log might feel dry while the core still holds moisture, and you often won't know until you're trying to get a fire going. Seasoned firewood is another term for the same thing. It's not necessarily bad, just harder to guarantee consistent quality without a controlled drying process.
What is kiln dried firewood?
As the name suggests, kiln-dried firewood goes through a heated chamber that controls temperature and airflow throughout the process. The temperature is usually maintained at about 170 F; applying heat speeds up the process while removing more moisture compared to air drying. As a result, the moisture content is usually below 20% and closer to 15%.
Because conditions are controlled, every load comes out the same regardless of season. There's no variability depending on how the wood was stacked, how wet the summer was, or how long it sat. Kiln-dried hardwood (birch, oak, and ash) gives you reliable heat and a clean burn.
Why moisture content matters
Wood with high moisture content just doesn't burn efficiently. Most of the energy goes into removal of moisture before the wood produces any real heat. Wood with 30% moisture delivers roughly 30% less usable heat than wood with 15%, which adds up quickly over a winter.
Burning damp wood also produces more smoke, builds tar and creosote in the flue faster, and blackens stove glass more quickly. The Solid Fuel Trade Group recommends keeping your firewood below 20% moisture, noting that levels below 15% yield the absolute cleanest results. Kiln-dried firewood consistently hits that. Air-dried wood often doesn't.
Kiln dried vs air dried at a glance
| Kiln dried | Air dried | |
| Moisture content | Below 20% typically | Varies, often 20 - 30% |
| Lighting | Quick and reliable | Can be slow, especially if damp |
| Heat output | High, consistent | Lower, less predictable |
| Smoke | Minimal | More, particularly at first |
| Stove glass | Stays cleaner longer | Blackens faster |
| Chimney build-up | Less tar, fewer sweeps | More build-up over time |
Is kiln dried worth the extra cost?
Admittedly, kiln dried firewood costs more upfront. However, because it burns with such high efficiency, each log yields significantly more usable heat, meaning you burn through your winter supply more slowly. When you factor in fewer chimney sweeps and fewer stove maintenance costs, the price gap narrows quickly!
While it makes a noticeable difference for open fires, kiln dried wood is arguably the best choice for wood-burning stoves. Plus! It’s also carbon-neutral when sourced sustainably, making it a smarter choice for both your home and the environment.
Kiln dried firewood from Monahan's
We at Monahan's have been supplying fuel and firewood across Ireland for over 50 years now. We stock kiln dried birch, oak, and ash, that are dried to below 20% moisture (as certified by Ready to Burn and recommended by EPA Ireland) and deliver nationwide in crates, bags and bundles.
Frequently asked questions
How do I know if my firewood is dry enough?
A moisture meter is the most reliable check. You're looking for a reading below 20%. Without one, dry wood feels light for its size, sounds hollow when two logs are knocked together, and has visible cracks at the ends. Wet wood is heavier, often darker at the cut ends, and steams or hisses in the fire.
Can I burn air dried wood in a stove?
Yes, if it's genuinely dry. Wet wood accelerates tar build-up and can void a stove warranty. If you're not certain of the moisture level, kiln dried is the safer option.
Is seasoned firewood the same as air dried?
Yes, the terms mean the same thing: wood left to dry over time, typically 12 months or more. How dry it gets depends on how it was stored and the weather it dried in.
