The seasoning process helps to naturally dry out wood so that it can be used effectively as firewood.
There are recommended moisture levels for firewood but the seasoning process can only bring the moisture content of wood down by so much.
So what is the moisture content of seasoned firewood?
The moisture content of properly seasoned firewood should be under 20%, as firewood burns its most efficiently between moisture content levels of 15% and 20%. Seasoned firewood typically won’t drop lower than around 10% moisture content because of the humidity of the atmosphere.
There are many factors that influence the moisture content of seasoned firewood and so we’ve explained in more detail below what these factors are, why properly seasoned firewood should be a certain moisture level, what happens when firewood is too wet and what affects how quickly firewood seasons.
Moisture Content Of Seasoned Firewood
Trees have a natural moisture content level that fluctuates year round, and the actual moisture content of the wood can vary depending on the species of tree and how healthy it is.
The starting moisture content of wood can also be influenced by the time of year the wood is cut. Natural moisture levels of trees are higher during the spring and summer months but drop during winter.
It’s therefore preferable to cut wood during winter when moisture levels are at their lowest. The seasoning process can then be started in early spring, and the upcoming warmer weather and lower starting moisture content helps to speed up how quickly the wood dries out.
Whatever time of the year wood is cut, it will have a moisture content that is far too high for it to burn efficiently on a fire.
As an example, we cut a branch from a tree on our property in early spring to test its moisture content using our moisture meter.
This particular piece of wood had a moisture content of 45%. If used on a fire this piece of wood would have burnt highly ineffectively. It will have struggled to catch fire, struggle to burn, produced more smoke compared to a dry piece of wood, and the amount of heat being produced would have been far lower.
The Environmental Protection Agency states that firewood burns its most efficiently at 15% – 20% moisture content.
Within this moisture content range, the amount of water in the wood is low enough for a fire to burn the wood without any major issues, while also being high enough so that the wood doesn’t burn too quickly.
In order for wood to reach this moisture content range it must be dried out through a process known as seasoning, where the wood is left outside under the right conditions to help naturally lower the moisture content of the wood over a certain length of time.
The time it takes for wood to dry down to recommended moisture levels can vary depending on a number of factors, such as:
- The starting moisture content of the wood.
- How well setup the wood is to be seasoned.
- Whether hardwood or softwood logs are being seasoned.
- The climate.
As each of these different variables need to come together for wood to properly season, the moisture content of seasoned firewood can differ between each situation. After the same period of time, some logs may still be too wet to use as firewood and some will have reached recommended moisture content levels.
The moisture content of properly seasoned firewood will also be around 15-20% in line with guidelines for burning wood, but the time it takes for wood to reach this level can vary.
The moisture content of wood dried out through the seasoning process will also never go below a certain level.
The humidity of the atmosphere means that seasoned firewood will always retain some sort of moisture content. From our experience we’ve found that some of our seasoned firewood has never dropped below 10%, even through it had already fully seasoned a number of years ago.
When firewood is kiln dried, the wood can reach even lower moisture content levels. One of the bags of kiln dried hardwood logs bought from a local store contained wood that was so dry our moisture meter couldn’t give it a reading.
Our moisture meter only gives readings down to 6.8% meaning that these logs had been dried out to below 6.8% moisture content.
Firewood typically won’t be able to reach these low moisture content levels through seasoning because of the moisture in the air. You can expect you logs to be fully seasoned by the time they have reached below 20% moisture content.
If you’re seasoning your own firewood then you should be storing it in the right conditions to allow the wood to reach the recommended moisture levels for firewood.
Here’s how we season our own firewood:
To help our firewood to dry out and reach 20% moisture content as quickly as possible we ensure that:
- The wood is placed on a dry platform or raised up off any moist ground to help prevent water from seeping back up into the lower layers of the log stack.
- At least one side of the logs stack is open to the air, allowing both the wind and sun to dry out the wood throughout the year, even in winter.
- Covered over by an overhang from the adjacent structure to help keep the wood from the rain and snow. A tarpaulin sheet can also be used but must not cover the whole of the stack otherwise moisture will build up and the wood can start to go bad, rather than dry out.
If you’re buying in your firewood then you should look to buy ‘well seasoned’ firewood. This typically identifies wood that has been dried out to recommended moisture content levels.
You may find that the moisture level of some bought ‘seasoned firewood’ to be higher than 20%. Simply leaving firewood to season for a while longer will help to bring moisture levels down to the recommended 20% or below.
If you aren’t burning firewood that is at recommended moisture content levels then you may notice that your fires are starting to struggle. This is because the fire is using more of its energy to burn off the excess moisture before it can properly combust the wood.
You don’t want to be burning any wood with over 25% moisture content as the wood will become progressively harder to burn. Poor combustion of wet wood will lead to more smoke being produced and less heat being generated by the fire.
Whether you’re seasoning your own wood or buying it in, you’ll want to invest in a moisture meter to ensure that you’re only using wood that is dry enough to burn efficiently.
A moisture meter is an inexpensive but essential tool for any home and will help you to have more successful, cleaner and hotter fires.
Our moisture meter is the best thing that we’ve bought for our fireplace.