Everyone is aware that firewood must be stored correctly in order to dry well. The residual moisture that is still present in the wood when you throw it into the oven or fireplace also determines how efficient it ultimately is. It is an important point that you can take into account when purchasing or by storing your wood correctly. We summarize what influence theWood moisture in firewoodon energy efficiency and how you can measure the residual moisture.
Wood that is too wet burns harder than wood that is well dry, reducing its ability to provide warmth. So the burning wood you ultimately paid for doesn't give off the heat it should.
But firewood that is too dry is also not a good idea, because in this case it burns too quickly, which shortens the heating time. So you have to refill more often and use more logs than if the wood was optimally dry.
In addition, firewood that is too moist produces even more harmful gases and increased soot. This is harmful to the environment and also pollutes the chimney and other parts of the stove system more quickly (up to three times as harmful to the environment and polluting).
How much residual moisture in firewood that is freshly purchased?
A good question, because ultimately you would like to know whether and for how long the wood will lastmust be stored, before you can use it for heating. But of course that depends on how long it was stored by the seller and, above all, where. Freshly cut wood has a different moisture content than wood that has been in storage for a year, and wood from storage has a different moisture content than wood stored in the forest. And then sometimes firewood is sold that has been dried more quickly in an artificial way.
Wood moisture values for firewood as a guide:
- Freshly cut wood contains 65% moisture.
- It is approximately 40 to 50% if the firewood is stored in the forest.
- 30% contains storage wood and if it is marked as “air-dried” it is 20 to 25%.
How dry does firewood have to be to burn?
- 18 to 20% wood moisture content for firewood is optimal for use directly for heating. This is the maximum value that chimney sweeps recommend, while the Federal Immission Control Ordinance prescribes a maximum value of 25%. On the whole, however, only 18 or less percent is considered actually dry and is the correct moisture content for firewood.
The price also depends on all these factors.
How long wood has to dry to reach these percentages depends on various things, such as the nature of the wood and of course the storage conditions before and after purchase. As a rule, however, one to two years should be taken into account.
Calculate and measure wood moisture for firewood
There are various ways to test, measure or calculate the moisture content of firewood. We summarize some methods:
- Measure the moisture content of firewood using a measuring device
The most accurate and safest method is to determine the wood moisture using a measuring device. This is also not an expensive investment, so it is definitely worth it. The device has sensors that you simply hold against the log so that the moisture content of firewood can be displayed. Always measure several places and also inside by opening the log.
Alternative options for determining the moisture content of firewood are less precise, but they can still give a certain idea. These are:
- Use your senses
This doesn't give you a percentage, but it's still an option. Your sense of sight as well as your sense of smell and touch are your helpers here: The surface of the log should be clean (noMold or fungus) and have clearly visible annual rings and cracks at both ends. Well-dry wood is also light in color (kind of like honey) and feels hard and dry. If you smell the smell of resin, let the wood dry further as it will not have dried sufficiently. Firewood with wood moisture that is suitable for burning no longer smells like resin.
In addition to these properties, dry firewood also has a certain sound when you knock on it vigorously or simply hit two logs together. This is hard and the sound still lingers. However, a higher moisture content in firewood produces a dull sound. However, the right sound is no guarantee that the core of the log is sufficiently dry.
You can also determine whether the firewood is still too wet when burning. First of all, it is of course harder to light and it hisses as the water evaporates. Take a look at the smoke coming out of the chimney: it is black when the wood is wet, white when it is sufficiently dry.
- Dishwashing liquid
It sounds a little strange at first, but it actually iseffective toolIf you want to find out whether the moisture content of firewood is already sufficiently low. You need a single drop for this. Drop this onto one end of the log and rub the product over the entire surface with your finger. Place the other end firmly against your mouth and blow strongly against it. Dry wood is more permeable to air than damp wood. If bubbles and/or foam appear on the detergent side, you can assume that the wood inside is well dried and has a residual moisture content of no more than 20 percent.
