With the increase in oil prices and the depletion of oil reserves, many people have turned back to solid fuel over the past few years. Wood is becoming a favourite as it is clean, renewable, easy to store, and can give a warm, lasting, fire. Whether you burn wood in a fireplace, stove, or furnace, good quality firewood is the key to convenience, efficiency, and safety. Most stove manufacturers recommend dry hardwood logs. What exactly are dry hardwood logs and where can you get them?
There are three main considerations when deciding which wood to buy:
Moisture content: This is the percentage of water in the log. The lower the moisture percentage, the higher the heat output from the log. Freshly cut logs have a moisture content of 50 to 70 per cent, and are unsuitable for burning as all of the energy is lost in the process of evaporation. Moreover, the burning of wet wood causes badly smelling gases to be released and a thick layer of tar will deposit on the stove panels and in the chimney. Most stove manufacturers recommend logs to be less than 20 per cent moisture. These will burn cleanly with minimal smoke, and leave only a small amount of ash, while maximising the heat output.
The wood species: Wood falls into two categories: hardwood and softwood. The hardwood used for firewood is usually ash, oak, beech, birch, or hornbeam.
It is not recommended to burn any treated wood such as scrap wood, dyed wood, impregnated or preserved wood, plywood, or chipboard. The fumes of these, as of synthetic materials and household wastes, are highly polluting for your stove and your chimney, and the environment. They can also cause chimney fires.
The price: The final consideration in buying firewood is to measure the quantity so you can compare prices. Here there are no consistencies, so the buyer must be aware of what quantity exactly is being quoted for. Firewood may be sold in bags which are either tightly stacked, or loosely filled with varying quantities. Larger quantities can be bought in trailers which are loosely filled, or in large crates which are neatly stacked. There can be up to 40 per cent more wood in a crate that is neatly stacked than in one that is loosely filled! Weight is not a good measure as the drier the timber, the lighter it is. Volume is the best way to measure firewood. The recommended measure is a metre cubed of stacked timber. This is one metre wide by one metre deep by one metre high of neatly stacked logs.
Generally, the firewood available on the Irish market falls into the following categories:
Kiln dried hardwood logs — these are usually ash, oak, beech, birch, or hornbeam. After the logs are cut and split they are placed in a kiln at about 160º C, and allowed to dry until the water content in the log is reduced to less than 20 per cent. Freshly cut timber has a water content of about 50 to 70 per cent. A further benefit of this process is that any insects present in the wood are killed. Of the above wood types, ash is a favourite of many as it has good burning properties, and has the least amount of sparking.
Seasoned hardwood logs — these are the same timber species as above, but the logs are left to dry in the air. Depending on the climate, it can take one or two years for the wood to dry. The moisture content of seasoned hardwood is usually 20 to 35 per cent depending on air humidity, the length of drying time, and other drying conditions.
Freshly cut hardwood logs — these are logs that have been cut within a few months. They are not suitable for burning as they are too wet, and are bought with the intention of storing them in a covered and well ventilated area, and allowing then to air dry for at least two years. Split logs will dry faster. The moisture content achievable in Ireland is usually 20 to 35 per cent.
Seasoned softwood logs — usually pine or spruce from native forests. The moisture content achieved is usually 20 to 35 per cent. As softwood is less dense than hardwood, it burns faster and does not form the bed of red nuggets at the base of the fire that you get from hardwood.
Freshly cut softwood — this is not suitable for burning as it too wet, and must be seasoned for one to two years in a covered and ventilated area.
Unfortunately there is no regulation of the firewood industry in Ireland, and consumers are often unaware of the quality and quantity they are buying. Only buy firewood from reputable sources. Always ensure that the moisture content is less than 20 per cent. Check whether it is neatly stacked, and compare prices by the metre cube. Remember that hardwood will last longer than softwood. After that put up your feet and enjoy the heat!