Moisture meters can be considered as an essential tool for any wood burning fireplace or stove.
Many problems associated with wood burning stoves and fireplaces can be associated with burning firewood that is too wet to burn efficiently.
Moisture meters help to identify the exact moisture level of any piece of firewood; allowing you to make a more informed decision on whether any logs would be too wet to burn.
As burning wet wood can make a fundamental difference to whether a fire will be successful or not, including going out or smoking too much, we always use moisture meters to check the moisture level of our own firewood before burning it in any of our open fireplaces, wood burning stoves or multi fuel stoves.
We’ve therefore put together this complete guide to using moisture for firewood to discuss and explain using our own examples:
- What a moisture meter is and what it does.
- Why you should be using a moisture meter to check your firewood before burning.
- How to use a moisture meter.
- What a moisture meter should read for firewood.
- And more.
Moisture meters are an essential tool for any wood burning fireplace or stove.
See our recommended moisture meter here along with all of our other recommended fireplace & stove tools.
What Is A Moisture Meter?
Moisture meters are an electronic device, typically small in size, used to measure the moisture level of certain materials. Moisture meters are commonly used for testing the moisture level of firewood to gauge whether it would burn well or not.
A moisture meter is a small and relatively inexpensive tool that can be used to measure the moisture content of materials such as timber and brick.
For wood burning appliances such as fireplaces and stoves, a moisture meter helps to identify the moisture content of firewood.
We always use a moisture meter to check whether our own firewood is ready for burning.
The moisture meter we own and use is shown above. It came in a small box as shown below.
Our particular moisture meter has the following options, many of which are standard across the range of moisture meters available to buy:
- Checks the moisture content (in percentage %) of wood fuels, structural timber and brickwork.
- Measurements provided on screen within 1 second.
- Ability to measure the temperature of the room in Celsius or Fahrenheit.
- Measuring range of between 6% and 48%, with accuracy +/-2%.
The figures and specs are for our particular model of moisture meter, but you can expect that in general most meters will be able to identify the moisture level of a few different materials, have a set moisture range with accuracy, and potentially have other features such as being able to measure room temperature.
Moisture meters are electronic devices and so they’ll typically need batteries to work. Ours didn’t come supplied with them.
Our moisture meter also came with a bag, but whether one is supplied or not will depend on the brand and model.
What Does A Moisture Meter Do?
Moisture meters read the moisture level of certain materials such as timber and masonry. Moisture meters typically give the moisture reading as a percentage, which can be used ascertain how dry the material being tested is.
The purpose of a moisture meter is to provide the user with a moisture reading of the particular material being tested.
A moisture meter is a very focused tool that really only serves the purpose of identifying the moisture level of certain materials. However, this isn’t such a bad thing.
A moisture meter can be very good at its job and, as we explain later within this article, understanding the exact moisture level of a materials will help you to identify what properties that material currently has, for example how well a piece of firewood will burn; whether it will burn poorly if too wet or very well if low enough in moisture.
Our own particular moisture meter can give an accurate moisture reading of wood of between 6% and 48% with an accuracy if +/-2%.
Our moisture meter can also give us a reading for the moisture level of walls at between 0.1% and 11%, with an accuracy of +/-0.4%.
We simply need to switch between modes on the device to be able to go between testing the different materials. We haven’t yet needed to use this meter on walls as we primarily use it to test our firewood, but is a nice addition if we ever need to.
Many moisture meters also have other additional testing features that supplement the ability to read moisture levels. For example, our moisture meter can also read room temperatures in either Celsius or Fahrenheit; useful for when we want to quickly know the temperature of any room.
Our particular model of moisture meter also has the following additional features that you may find on other models:
- Colour changing display (red, amber and green) to easily identify moisture levels.
- Auto power off.
If you have been looking at moisture meters then you may have comes across traditional pinned and also pinless versions of moisture meters.
They both achieve the same thing (providing you with a moisture level) but pinless moisture meters don’t leave any pin marks but may cost more to buy.
Our own moisture meter has pins and so we need to press these pins slightly into the wood we’re testing, but as it’s firewood it doesn’t matter because it’s going to be burnt anyway.
Why Use A Moisture Meter?
Using a moisture meter to identify the moisture level of firewood helps to determine whether that piece of wood is dry enough to be useable on fires and burn efficiently. Burning firewood too high in moisture content can lead to numerous issues.
A moisture meter can be considered to be one of the most important tools available when burning firewood in any form of appliance such as open fireplaces and wood burning stoves.
The requirement for firewood to be low enough in moisture content to burn effectively is often overlooked, and burning wet firewood can lead to many common issues experienced with wood burning fireplaces and stoves, including:
- Finding a fire hard to catch alight and get going well.
- Ongoing poorly burning and smoldering fires.
- More smoke being produced than usual.
- Less heat being generated.
- Greater and quicker creosote build-up.
A moisture meter can help prevent some, if not all, of these things from occurring resulting from burning firewood that is too wet.
We always use a moisture meter to test all of our wood as it allows us to accurately test the moisture level of any piece of firewood that we’re planning to burn. You get a reading very quickly with moisture meters, and the color code system on our own one makes the process even easier and quicker.
As we season a lot of our own firewood, this information aids us in understanding whether the wood has been properly seasoned or not and whether it needs more time to season.
For more information see exactly how we season our own wood here.
A moisture meter also allows us to test any firewood that we buy in.
Even though you may be buying ‘seasoned’ wood it may not always be the case that the wood has been seasoned long enough to really be effective for use as firewood. We therefore test a random sample of any logs we buy in to see how the whole lot fares in terms of moisture content overall.
What Should A Moisture Meter Read?
A moisture meter should read below 20% for wood for it to be classed as ready to burn effectively as firewood. Any firewood under 20% can be classed as acceptable but wood can become progressively harder to burn to as moisture levels increase above 20%.
The Environmental Protection Agency (EPA) explains that the ideal moisture range for firewood is between 15% and 20%.
Furthermore, our own moisture meter provides a color code system that is associated with the moisture level reading:
- Green for moisture levels between 6% and 15%.
- Amber for moisture levels between 15% and 20%.
- Red for any moisture levels over 20%.
A ‘Low’ reading is given for any moisture levels below 6%, which we’ve encountered a few times with very dry kiln dried firewood.
The instruction manual for our particular model of moisture meter explains that:
- Green (6%-15%) is firewood that is ‘good and perfect for burning with optimal heat’.
- Amber (15%-20%) is firewood that is ‘OK to burn and should give OK performance’.
- Red (20%+) is firewood that ‘should be allowed to dry further before use’.
As a rule of thumb, we never try to burn any firewood that is over 20% in moisture content as it can lead to the problems we outlined earlier in this article.
However, as it can become progressively harder to lower the moisture level of firewood through seasoning below a certain level due to the humidity of the atmosphere, we’re also happy to burn any firewood that reads green or amber when testing (anything below 20% moisture), which is in line with what the EPA recommends.
Do Moisture Meters Work (Are They Accurate)?
Moisture meters will typically provide a good moisture level reading of materials when used as recommended by the manufacturer. The accuracy of a moisture meter will depend on the model but can be within a couple of percent.
Moisture level readings for firwood isn’t an exact science but the reading that a moisture meter can give you (typically within the accuracy of a couple of percent) can give you a quick indication of whether a piece of firewood will burn well or not.
We’ve been using moisture meters for our firewood for years and we’ve never been let down by a false reading.
Can Moisture Meters Be Wrong?
Moisture meter readings can be wrong if not used correctly.
Moisture meters with pins usually need to be pressed into the material by a certain distance in order to display the most accurate reading.
The manufacturer of our own moisture meter explains that when using the moisture meter to:
‘Push the probes [pins] 1mm into the wood, or till it makes firm contact with building materials.’Valiant
We’ve found that if we don’t push our moisture meter far enough into our firewood then it will be unable to provide a reading, displayed as ‘Lo’.
How To Use And Read A Moisture Meter For Firewood
For pinless moisture meters, turn the device on and press the end of the device against the material to get a moisture reading. For moisture meters with probe pins, press the moisture meter pins slightly into the material for it to provide a reading.
To use a moisture meter to read the moisture level of a piece of wood or masonry:
- Turn the moisture meter on using the power button.
- Ensure that the moisture meter is on the right setting for the material being tested.
- Remove the cover to the probe pins, if required.
- Press the pins on the moisture meter into the material, or press a pinless moisture meter up against the material, to get a moisture reading.
To read a moisture level, use a moisture meter as described above or as set out within the manufacturer’s instructions, and check the display on the device for a moisture reading.
For our own moisture meter when testing firewood we ensure that it is set to wood moisture content testing mode (indicated by the tree symbol on the display) and then press the pins into the wood and a moisture reading will be provided within a second.
For more information see our more in-depth article on what the moisture level of firewood should be and how to test.
How A Moisture Meter Works
Moisture meters with pins check the electrical resistance of the material being tested and provide conductivity as moisture reading. Pinless moisture meters test the relationship between the material and the moisture to provide a reading.
Moisture meters that have probing pins (like ours) essentially create a small electrical circuit when pressed into a material and tested.
Moisture is a great conductor of electricity and so a moisture meter is able to read how conductive the material currently is based on the level of moisture and output that as a moisture level reading.
Pinless moisture meters can use a magnetic field to detect moisture close to the surface of the material and also output that as a moisture level reading on a digital display.
Pinned moisture meters require being pressed into the material to give an accurate reading.
Pinless moisture meters don’t have pins and so the end of the device (where the receptors are) simply needs to be butted up against the material for a reading to be provided. As such, pinless versions of moisture meters are non-invasive and won’t leave a ‘pin mark’ like traditional pinned moisture meters will.
What Is The Best Moisture Meter For Firewood?
Our recommended moisture meter can be found here, along with all our other recommended essential fireplace and stove tools.
The best moisture meter for firewood is one that provides you with the most accurate reading that you require, one that is either pinned or pinless depending on your preference, and one that has any other features you’d like to have such as the ability to test the temperature of a room.