The importance of burning dry wood
With any wood fuel and firewood logs in particular, the most important thing to consider is the moisture content. When burning wood some of the calorific value of the wood is used to drive off the water content within the log.
When freshly cut a tree can have a moisture content anywhere between 40 to 60% depending on the species of wood and time of year the tree was felled. To put this into perspective 10kg of unseasoned wood could contain as much as 6 litres of water. Ideally wood should have a water content of 20% or less.
When burning logs, the moisture is driven off and forms steam, this steam can condense in the flue system and react with the volatile organic compounds within the fuel to form sticky deposits (tar and creosote).
Over time these can block the flue and just as importantly these deposits contain unburnt fuel and therefore increase the risk of a chimney fire. If your stove is connected to a stainless steel flue system (flexible liner or twin wall) these deposits are corrosive and will attack the liner.
This is why it is important to ensure that you only burn seasoned wood and have your chimney swept regularly.
So in summary – make sure you only burn seasoned or kiln dried wood with a moisture content of less than 20% (a good investment would be a moisture meter so that you can check the moisture content yourself) and ensure you get a chimney sweep to sweep your flue.