Wednesday 18th January 2017
If you use logs or wood briquettes as a primary source of heat for your house in cold months of the year, you are likely to search for a product that comes out cheaper than gas heating or using electricity. In this case, you will look for a good quality product at a reasonable price to buy in bulk. You would also need space to store your logs or briquettes.
If heating your house is not your primary goal and you would burn logs only occasionally, then you would want to be able to buy small quantities of high quality product (such as kiln-dried logs) for enjoyment.
Apart from the price matter, there are a number of questions that need to be considered when choosing logs:
- Size? Check instructions for your stove to decide on the right size of logs. Wood briquettes are normally as large as or smaller than logs (especially the RUF type or brick shaped briquettes)
- Sawdust briquettes, green or seasoned logs? Very important as the moist content of wood has the direct impact on the calorific value or the amount of available heat per unit (volume) of fuel. Any water in green wood will need to boil away first before wood will start burning, hence, reducing the eventual useful heat released. A fresh green log of about average moisture content has only about half the energy content of an equivalent well-seasoned log and a quarter of energy content in a wood briquette made from pressed dried sawdust. Also to bear in mind is the tar and smoke produced when burning green wood – these can be corrosive and may potentially damage the lining of the flue and blacken glass in stoves. If you decide to use cheaper green logs, you will need to dry them yourself. Seasoned wood and especially wood briquettes are more heat efficient and easier to handle in this respect.
- Hardwood or softwood? When buying logs, it is common for the seller to specify whether their logs are from hardwood or softwood tree species (or mixed). Very broadly, the main difference is that hardwoods (mostly deciduous, broadleaved tree species with a few exceptions such as poplar, willow and eucalyptus) tend to be denser than softwoods (mostly evergreen, coniferous species with again a few exceptions such as yew or larch). For a log user, this means that a tonne of hardwood logs will take up a smaller space than a tonne of softwood logs. Also denser wood tends to burn for a longer period of time meaning fewer ‘top ups’ are needed to keep a log stove burning for a given length of time. On the other hand, softwoods tend to have a higher proportion of resins and volatile oils, which result in a slightly better calorific value (more heat) than hardwoods for the same weight of wood. In reality, at the same moisture content, there is little variation in calorific values among all of the species of wood when it is well-seasoned. This also applies to compressed wood briquettes.
- Are you buying by weight or volume? Check with the supplier or on their website. If you buy wood by volume you will receive more kilowatt hours (kWh) of heat from a cubic metre (m3) of hardwood than softwood (at the same moisture content). This information is also important because you will need space to store logs.