Logs
Sophisticated, controllable log boilers are available which can provide central heating and hot water.
The primary consideration with logs is that they must be manually loaded once or twice a day. Larger boilers (above around 80kW) will require considerable amount of man hours for stoking. This limits the application of log boilers to situations where daily availability of labour to load the boiler is not a problem.
Logs sizes required by boilers range from 30 cm to 50 cm. Their width should be between 6 cm and 8 cm. Use consistent log sizes to achieve uniform burning at an even rate. Logs should be seasoned by the supplier for one or two years prior to sale.
It is advisable to buy logs by volume rather than weight, since moisture content (and therefore weight of water within the logs) can vary.
As hardwood species are generally denser than softwood species, a tonne of hardwood logs will occupy a smaller space than a tonne of softwood logs. Dense woods tend to burn for a longer period of time than softwood meaning fewer ‘top ups’ are required to keep a log stove burning for a given length of time. If you measure wood by volume you will receive more kilo-Watt hours (kWh) of heat from a cubic metre (m3) of hardwood than softwood, though this will tend to be offset to some extent by the higher calorific value of many softwoods.
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