All our advice for choosing the right firewood

All our advice for choosing the right firewood

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Wood heating is on the rise. Today, it equips 1 in 4 households. The Grenelle's objective is to encourage its use to equip 9 million households by 2030. These figures impress, and this is not the irreversible increase in the cost of fuels fossils that will curb the craze for this energy. All the more reason to take a closer look at the quality of this firewood. How to choose it? What are the criteria to remember? For what cost? How much? Is it green? Under what types of packaging is it found? These are all essential questions that we will address in this dossier. What vocabulary? The pros use specific measurement units for wood. The first thing is to know what it corresponds to: - 1 cubic meter = 1 cubic meter of wood (for logs of one meter, if the logs are 33 cm, the volume is about 0.7 m3, because there less vacuum between the logs) - 1 cord = 3.62 steres (varies by region) Speak preferably in cubic meters, this will avoid surprises!

The choice of gasoline

In the case of logs, the essence of the wood is a criterion that should not be overlooked, as it directly influences the comfort of use. This is even more true with an open chimney, in which it will be necessary to avoid at all costs the woods which "burst" such as the chestnut, the plane tree, or certain conifers, with the risk of projection of sparks and the associated dangers. The particular case of the open fireplace is marginal today, we should no longer heat a house with this type of fireplace. For convenience, we will distinguish wood in two categories: hard wood and soft wood. Hardwoods are recommended for their performance and their burning time. This is the case, for example, of hornbeam, olive, oak, ash, beech, maple and apple. As for softwoods, they burn quickly, but their calorific value is low. This appellation covers in particular spruce, fir, birch, poplar and cedar. Their ideal use? The ignition of the fire. A word about the risks: All types of wood, but more particularly softwoods, promote creosote deposits in chimney flues. Creosote is a very flammable substance and, when it is too important and reaches its point of ignition, it causes what is called a chimney fire. Likewise, its accumulation in the conduits can cause a blockage, and cause carbon monoxide poisoning. It is for these reasons that it is recommended to have your chimney swept by a specialist (compulsory insurance) each year and to ventilate the house, even in cold weather.

Humidity: what degree is acceptable?

If gasoline is an important criterion, the moisture content of the wood is absolutely essential to ensure proper combustion. As a general rule, logs must be delivered with a threshold of 20% humidity, the same applies to shredded wood (forest chips). Wood pellets (pellets) are given for a rate of less than 10%, which explains their higher yield. Unsplit logs must dry at least two years before being marketed and used, this drying time being essential to around a humidity level of 20%. Green wood (drying time less than 5 months) that has not sufficiently dried can contain more than half its weight in water. Such wood would lose all its calorific value, since the energy produced would be absorbed by the vaporization of the water it contains. When it is possible to check, it is also preferable to buy a wood cut in winter, when the sap is absent: it will dry faster. In addition, a damp wood causes smoke, poor combustion, excessive consumption, creosote (see above), it blackens the panes, etc. The bottom line is that the drier the wood, the more it will heat.A little trick to check the humidity of a wood? Tap two logs against each other, the noise should be dry and frank. If it is deaf and insidious, it is not dry enough.

The cost: is wood the most economical energy?

The European Gallery of Forest and Wood has provided us with a very explicit little table which, for each type of energy, compares the cost and the quantity required to bring to a boil 25 liters of water. There are three main types of wood conditioning: logs, pellets and chips. For this example, the cost of electricity would be € 0.30.
Some prices (in 2012): - The average cost of the cubic meter of wood all regions combined is 45 euros (from 30 to 60 euros). The essence of the wood, its duration of storage, the size of the logs and its transport must be taken into account. - The average cost per tonne of loose pellets is 205 euros (from 180 to 230 euros) and 275 euros in bags (from 250 to 300 euros). - The average cost of wood chips (shredded wood) is 55 euros per tonne (30 to 80 euros) depending on the humidity. These are indicative prices subject to variations depending in particular on transport.

Standards: what are those applied to wood?

Wood is no exception to standardization. If you buy your firewood from approved distribution channels, it must be NF standardized. Thus it is classified according to 3 groups for essences, and 3 classes for humidity. This classification makes it possible to know the calorific power in kWh of a cubic meter of wood (1 cubic meter) according to its essence and its humidity. Gasoline groups Group 1 : oak, hornbeam, elm, beech, ash, maple. Group 2 : chestnut *, locust (or false acacia), wild cherry, and fruit trees. Group 3 : Softwoods (spruce / fir / pine / larch ...) and other temperate hardwoods (birch, poplar, plane tree *) (*) beware these woods are not suitable for open hearths. Classes for humidity It is measured on the gross mass. Class H1 - Humidity less than 20%> can be burned immediately. Class H2 - Humidity between 20% and 35%> recommended to wait 6 months for drying. Class H3 - Humidity higher than 35%> recommended to wait one year of drying.

Quantity: how to estimate my consumption?

Difficult to say what you will consume. What you need to know is that at equal weight and equivalent humidity percentage, there is little difference in calorific value between the different wood species. On the other hand a ton of oak represents a volume half less than that of the poplar, because of their respective densities. It's a bit of the story of the kilo of feathers and the kilo of lead! In summary, someone who warms himself with poplar will almost need twice as much wood as someone who warms himself with oak. So be careful to pay the right price depending on the gasoline. For information : - For decorative heating, a family uses about 6 or 7 cubic meters of wood per year. If you only heat with wood, it is not uncommon to use 14 cubic meters or more. - For a pellet heating, a family uses around 5 tonnes of pellets. - The case of shredded wood (chips) concerns more communities, rare are the individuals to use this mode of heating because of the consequent space necessary for storage! These are average values ​​collected from users.

Ecologically: is wood a green energy?

It is said that firewood is ecological. Ecological because its combustion emits as much CO2 as it absorbed during its life. If this is true, however, this point of view must be put into perspective. An average tree takes 30 years to become an adult, and it takes just a few hours of combustion to release the CO2 it has fixed during this period. It is therefore easy to understand that the repetitive use of firewood cannot be compensated for, even by newly replanted trees. In addition, the combustion of wood emits very many particles, hydrocarbons, dioxins, organic compounds, etc., which seriously pollute the air. It is not a question of giving oneself a bad conscience, but of being lucid about the fact that burning wood as a means of heating is not an act without consequences. Despite this, firewood can be considered as one of the least harmful means of heating with regard to CO2 emissions. It will be necessary to ensure that this wood is replanted or comes from coppice and that it comes from local sectors so as not to add the weight of a transport to the balance sheet. What you must remember,the drier the wood, the better the combustion, the less harmful its emissions . Ask for a wood heating quote.