Wood heating

Fuel is very important to achieve complete combustion. Not by its quality but by its water content, which should not exceed 15 to 20% of its weight. The essence of wood does not matter, it is the humidity that should be as low as possible. The mase stove can be powered by log wood or wood briquettes.

Chemical composition

Wood is a complex chemical molecular edifice with a high content of volatile materials. It produces:

  • 85% volatile material (67% of its energy)
  • 14% charcoal (33% of its energy)
  • 1% ash

Wood, gas bottleWood is “a gas bottle.”

The basic chemical composition of the different wood species in the anhydrous state (completely dry wood) is approximately the same:

  • Carbon 49%
  • Oxygen 44%
  • Hydrogen 6%
  • Azote 0.3%
  • Ashes 0.7%


The use of damp wood greater than 20% on crude oil is strongly discouraged for wood heating

  • Wood is an anhydrous fibre (sponge) with a water content on raw water in the range of 50-80%
  • Moisture causes the calorific value and quality of combustion to vary.
  • This water content is defined by:
Moisture on crude (wet wood) H – water mass / raw mass of wood

Moisture on raw is the value used in firewood.

Calorific power

The calorific power of the wood varies little depending on the different species. On the other hand, it varies in large proportions depending on its humidity.

Calorific powerThe resinous wood is suitable. It even has better calorific power.

PCI (humidity)

For equivalent thermal comfort, the consumption of freshly cut wood (45% moisture relative to gross mass) is about twice as high as the consumption of ready-to-use dry wood (less than 20% moisture relative to gross mass)

In short, the use of dry wood reduces its consumption of wood and makes it possible to have a clean combustion.

Your fuel

Your heat-accumulating stove can be powered only by logs or wood briquettes.

Wood in logs:

  • Only natural, air-dried wood with a maximum water content of 20% is suitable for your heat-accumulating stove. The right degree of drying is achieved after two years of storage outdoors, with a cracked wood, well ventilated and protected from the elements.
  • All types of wood are suitable, be it hardwood (beech, red beech, oak, pear, acacia, etc.). or soft wood: (spice, fir, pine, larch, poplar, birch, etc.).
  • The diameter of the logs can be up to 15 cm. You should also have about half a wooden stere in a thin section for ignition.
  • Depending on your project, your desires and your needs, the dimensions of your fireplace adapt to those of your logs: from 25 cm to 1m in length.

Wooden briquettes

  • Wood briquettes are produced by cutting sawmill waste. Please use only wood briquettes that have been certified to BE DIN 51731 and/or NUMM M 7135.
  • Note that the weight of each briquette should not exceed 1 kg (if necessary, divide the briquette).

Other fuels:

Important: Burning materials containing plastics, oils, glues, or wood treated or coated with varnish, demolition wood or old furniture can affect the longevity of your appliance: corrosive elements can attack the refractory elements of your stove. Also, the use of treated wood is prohibited. The combustion of such materials also generates polluting and toxic emissions harmful to health, the neighbourhood and the environment. Also by extension and precaution, even if with the naked eye, no treatment is visible, It is also forbidden to burn cardboard and pallets. You can view and download an information sheet on waste burning on the swiss-wood energy website



The burning of the wood takes place in three stages: drying, pyrolysis, oxidation.

The wood burns by giving as residue:

  • Ashes composed mainly of mineral materials
  • Smoke consisting mainly of conventional CO2, CO, NOx, H2O and N gas effluents as well as tars, acetic acids and dust

Burning wood

Drying and storing wood

Natural drying, i.e. in the open air, is the easiest way to dry wood. The wind, the sun are the best allies. Never store wood under polyane, nylon or unventilated space.

There are a few basic requirements to follow:

  • The wood must be stored in a ventilated area
  • The wood should be split (more evaporative surface).
  • The wood must be shaped to the length of use
  • The wood must wait at least 18 months before its use
  • The wood must be sheltered from the rain
Wood storage

Raised to avoid hair uplift, split, well ventilated, this wood is however not sheltered from the rain.

The hygrometrics of the wood are measured with a wood-burning hygrometer at the heart of the log.

For more information on wood fuel with graphics and other illustrations, here is the following link: wood fuel.