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Daniël Bos

Chimney fire causes?

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I definitely think a flue problem the twin walls are prone to it don't fit them any more due to the hassle I have had with them over the years. The last one which I was involved with we swapped it for a  proper masonary flue with clay liners in end of problem. The twin walls are insulated but only about 30mm of rockwool. I would try and insulate the flue as much as possible inside the property so the gases are kept as hot as possible when they leave the roof space.

I had one call back we had built a garden room which they had a wood burner installed by another company they said my roof was leaking as they had water running down the side of the flue and dripping off when it got to the bend. I stripped the slates off around the flue everything perfect you could see the beads of condensation on the outside of the flue in the roof space area which was only 400mm high . I packed rockwool round it problem solved.

 

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22 hours ago, Alycidon said:

 

 

16% is the maximum logs mc advised to use,   most KD I have seen is around 20%,  thats why I bang on about it.  Are the logs of a suitable diameter,  125mm/ 150mm average should be Ok.

 

A

16% might well be what performs best but it's just impossible for anyone in the UK to achieve drying or storing firewood outside. Equilibrium moisture content up in Central Scotland is well over 20% during winter (about 24% here at home, as we are in a cold spot and relative humidity stays high). How would you suggest we that people in the north of the UK or on the west coast achieve 16%? Genuine question, not being difficult :D

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30 minutes ago, Big J said:

16% might well be what performs best but it's just impossible for anyone in the UK to achieve drying or storing firewood outside. Equilibrium moisture content up in Central Scotland is well over 20% during winter (about 24% here at home, as we are in a cold spot and relative humidity stays high). How would you suggest we that people in the north of the UK or on the west coast achieve 16%? Genuine question, not being difficult :D

Big J

 

What is the current temperature and relative humidity where you are?

 

It's joiners and craftsmen that are most interested in equilibrium moisture content as  they can then make a judgement about how the finished article will "move" as the seasons change with central heating being also a factor.

 

As such the moisture content is often quoted as a % of the oven dry weight, rather than the % of the wet weight we tend to use.

 

So whilst the wet weight basis and dry weight basis converge at 0% a moisture content of a bit less than 17% wwb is equal to a moisture content of 20% dwb.

 

The equilibrium moisture content hardly changes with normal ambient temperature in UK, about 2% dwb between 0C and 30C so the main variable is relative humidity.

 

Here is Surrey it is 6C and RH is about 90%, because it is raining, so the equilibrium moisture content of wood should be about 22% dwb  18% wwb but as it takes time for the log to gain moisture on average in the winter it will be a bit lower, as long as it cannot be re wetted.

 

In high summer with a temperature around 20C and RH 40% it will drop to 8% dwb 7.4%wwb.

 

In winter when we need to burn logs I would expect it to hover just below 18% mc wwb.

 

In practise I have done rather badly with drying this year's logs, I'm not sure why but possibly too much oak which did not dry well

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It's much damper up here. We're 1.3 miles from the sea, which doesn't help.

 

Looking at the data from my weather station (s), the relative humidity averages over 95%, and can go a week or more at 100%. We're in a cold spot, so our temperature is usually 2c less than our friend who is 3 miles away. He has the same weather station. Average temperature since the start of November has been 3 celsius. As such, equilibrium moisture content is around 24%.

 

Summer is incredibly wet here too, to the point that keeping the house free of damp is tricky. RH in the house is usually over 70% through summer and whilst we do get days of 30-40% RH outside, more common is 70-80%. 

 

At the moment, the sawn timber I have in the barns is sat at 20-21% MC but that has crept up from 17% over summer. It never goes lower than that. The yard is a bit less damp than home (further inland and windier).

 

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