Freshly cut wood can contain 100% moisture. This means that the water in the wood outweighs the wood itself. Trying to build a fire from this wet wood is incredibly difficult, as you need to get rid of most of that moisture before the wood can burn properly.
This wet wood is often referred to as green wood and although it can still burn, it is much less efficient and less safe to burn than properly dried, ‘seasoned’ firewood.
The firewood we burn today should contain no more than 20% moisture or less and there is plenty of reasons why:
With so much of your fires energy being wasted in converting the water in the wood into steam, the burning of green wood is seen as the least efficient fire, and the least efficient way to heat a home. Vaporising a pound of water wastes around 1,200 BTUs, or British Thermal Units, a precise measure of heat. A pound of firewood that contains 20% moisture can provide around 7,000 BTU of heat.
Not only is it inefficient, burning wet wood can actually be harmful to our health. Wet wood produces much more smoke than dry wood does, in turn, it releases more pollutants and small particles into the air. Burning wet wood also causes a rapid build-up of creosote in your chimney which can cause a serious fire hazard.
If you aren’t sure whether your imported firewood is dry enough, check the ends of each piece; if small splits are evident it means the wood is probably dry, whilst a smooth texture will indicate that moisture is present. By knocking two pieces of wood together you can gauge the wetness by the sound it makes: wet wood creates a quiet noise, while dry wood makes a louder, knocking sound.