The Air Quality (Domestic Solid Fuels Standards) (England) Regulations stop small quantities (under 2 cubic metres) of firewood from being supplied where the moisture content is above 20%.
For more information please go to the Woodsure website.
The moisture content of a piece of wood is defined in two ways:
Wet basis which is a measure of the water in a log, expressed as the weight of water as a percentage of the wet/unseasoned log. (i.e. wood and water) Dry basis which is a measure of the water in a log, expressed as the weight of water as a percentage of the completely dry log. (i.e. just the wood)
Firewood is measured on a wet basis and although the new law does not mention what basis is used it is relating to fuel so it can be assumed the moisture content should be 20% wet basis.
One of the most common ways of measuring the moisture content is by using a pin moisture meter. These meters were originally sold for measuring materials used in construction where moisture is likely to be measured on a dry basis. Many wood moisture meters do not state what basis they use but even the ones now aimed at the firewood market are likely to measure on a dry basis.
(Wet basis moisture metres are much more expensive than the dry moisture metres)
WHY IS THIS IMPORTANT?
Well If you have a moisture meter which measures on a dry basis as most do it is worth noting a reading of 25% dry basis = 20% wet basis. Therefore if your logs are delivered and your (dry basis) pin moisture metre readings are 25% & less DRY BASIS that is in fact 20% & less WET BASIS therefore adequately seasoned.
Also worth noting is that if you buy a fairly cheap pin metre it is unlikely to be accurate as we have found in the past they often measure the wood at a higher moisture content than it is. We have been through many different moisture metres and our favourite by far is the IMEX MP100 moisture metre pro. You have probably seen Jake with his lime green pin metre !! It does test on a dry basis so as mentioned above you need to follow the under 25% rule!
Link https://www.imextools.co.uk/products/imex-moisture-meter-pro-mp100
You can convert from dry basis to wet basis using the following formula:
Wet basis moisture content =
(100 * Dry basis moisture content) / (100 + Dry basis moisture content)
25% dry basis converted to wet basis = 20%
(100 x 25.0) / (100 +25.0) = 20%
2500 / 125 =20
16.8% dry basis converted to wet basis = 14.3%
(100 x 16.8) / (100 +16.8) = 14.3%
1680 / 16.8 = 14.3
Thankyou for reading our post, if you have any questions do let us know !
Chloe & Jake
@ Baxter Logs