open vs lined chimney

[JanJonWestWales]

Not wanting to open a huge debate, but something has been occupying my mind.
Are there possible downsides to lining a chimney?.

Our Welsh farmhouse has a traditional "sime-fawr" huge Inglenook.
It is my understanding that originally this would have been pretty much alight 24x7, and would have emptied the room of damp air continuously up the open chimney
ie; with properly breathable walls - a properly breathable house....our holy grail
I assume it would have been similar for other occupied rooms (although not sure how the bedrooms would have worked)

I sometimes wonder if we have buggered up this mechanism?

In the modern way, we have installed a log burner, a tall flue pipe, boarded and insulated the inglenook ceiling, and of course an insulated lined chimney flue up to a top chimey plate.
We have of course used lime render inside and out, so at least we have the breathable walls, but where is that moisture going to go???
Surely a closed fire isnt going to suck much damp air into the fire, and up the flue?
Some heat will leave the room up through the chimney, but it wont be taking much moisture with it . That's insulation for you.

Not that I am going too...but shouldn't I remove the chimney lining, open up the inglenook, just have a flue pipe from the log burner up into an open chimney, and let the warm air + moisture flow upwards?
Very inneficient from a heat loss perspective,but great for damp control.

any thoughts?

http://blaencwmbychan.blogspot.co.uk

 

[noj]

Absolutely correct - a huge opening into the sky and a fire burning 24x7 certainly worked.

Reducing this with a liner extracts less damp air
Not running the log burner all day, every day, extracts less damp air

The dynamic has changed - but only time will tell if it's gone past a tipping point.

Good rain water drainage, a sound roof, mechanical extraction from kitchen and bathroom, not drying clothes indoors, not having a kettle simmering 24x7 and not having a great big hole under the Welsh sky coupled with keeping everything else as breathable as possible may well be sufficient to keep the moisture suitably low.

 

[JanJonWestWales]

We have a thermometer/humidity meter in the inglenook room, and when we arrive it is normally around 80-90% (if its been very wet, then it can get to 100%)
With a lit fire for a good while (and when its not too cold, an open window)..the humidity comes down to 60-70%.....after a few days it stabilises at 50-60%, never gets below this even in the summer.
As with most things ...what you measure - you manage, and I do tend to obsess on damp...suppose it comes with the territory

 

[Greg.Hobson]

We are somewhere between the 2 extremes, namely:

Unlined Chimneys - both downstairs in a 3-storey, solid stone walls, 800 foot up above Holmfirth.
Large but not huge fireplaces, maybe about 5 foot high by 4 foot across, stone pillars and mantels.
Register plates on each.
Modern stoves in each, the smaller a 5kw 5" flue, the larger 8kw with a 6" flue.
Exclusively wood fired.

We start lighting a stove when it gets cool - usually around October - as it gets colder we have more "2 stove" days when both are lit, Mostly January/February. The process reverses quite quickly through March with April seeing little use. At least 1 stove is lit (smaller or bigger - depends on the forecast for the day) around 08:00 and is kept going until around 22:00, fired in a way to encourage the production of charred embers that will then stay red hot until the next day, when the addition of more fuel and judicious use of the flue damper, air vents and lungs coaxes the whole cycle into action once more.

From Oct to Apr, no door in the house is left closed unless intentionally, i.e.The room is not in use (We have 5 bedrooms and, as I speak, there are just the 2 of us. With 4 adult sons, this changes dramatically at short notice).

From October through April, the feel of the house changes totally. The downstairs becomes warm and cosy, a diffused warmth that seems to ooze from the very walls themselves. There is no condensation - even in the kitchen/diner - unless heroic efforts have been expended in the kitchen. The house exhibits a distinct temperature gradient from around 20degreesC downstairs down to around 11/12 degrees in our bedroom, under the eaves at the top of the house (but we like it that way!).

This inverts from April to October, when downstairs is cool and, arguably, damp. This finds its most extreme form in a large patch in the front room carpet which we believe to be dampness and a wearing carpet (it's been down over 23 years). This damp patch disappears within 10 days of lighting the stove in that room.

From October, my hands get increasingly rough and dry. Probably mostly from handling the wood, but a degree I put down to the fact that the house is bone dry

Whilst I am totally with the measure it /manage it brigade, my weather station is on its last legs and refuses to do much except sit there, on the roof where I can't get to it! My Key measure is whether we use more gas in Winter than in summer. Most winters we don't.

Also, I assume you have already studied the relationship between changing air temperature and relative humidity. It is very enlightening to see how heating very cold air (drawn in through all that ventilation) ensures an almost endless capacity to absorb water as its temperature rises.

 

[Bogart]

Never ever been able to keep a wood burner ticking overnight so that it is still okay in the morning to add more logs.

 

[88v8]

Our cottage - two woodburners in what were inglenooks - is dampest in summer.
The rh gets up to about 75% and without the dehumidifier the cellar would be around 85%.

Now, with both stoves going in the evening it's creeping downwards.
In the dining room, 50%ish, in the sitting room which we burn for less time, around 55%.
By January it will bottom out at 45%.

When the woodburners are not lit, I keep the dampers open. That way they suck a little air from the interior.

It's also important to have air inlets of course. What used to be called 'draughts'.

Ivor

 

[Greg.Hobson]

Never ever been able to keep a wood burner ticking overnight so that it is still okay in the morning to add more logs.

I'm not saying I know but after becoming (IMHO) a real geek on the topic, I am about 50% successful.

First off, if it's windy overnight, forget it.

Second, my success rate was very low before fitting flue dampers.

Assuming the forecast is in my favour, I start as early in the day as possible and only when the whole setup (Stove, flue, etc) is up to working temperature, I set the flue damper to the minimum draw possible that will allow the stove to burn without smoke. This is visually recognisable because the flames go from lazy yellow to lazy blue. Maintain this blue flame burn by judicious setting of air vents and flue damper. If using wood, keep the bottom air vent closed, use only the top air inlet to allow air into the stove. When the flames die and the stove needs replenishing, I find there is a bed of embers on which to lay the next firing.

This bed of embers can be built up over the day such that the room for the next firing becomes limited by the depth of the embers. In effect, I create a layered fire in the stove - embers at the bottom, charring wood on top and dancing blue flames above the wood. In a perfect world, this would be pyrolysis - it is a long way from the ideal definition of the same ( burning organic material at high temperatures in the absence of oxygen) - but this is the model I keep in my mind.

I try to aim for the optimal point to be reached around 10pm. At this time, I don't put any wood on at all. I have found that the idea of "Banking up" the stove is a fallacy. In truth, the stove is already full of embers in such a state that they would make the best BBQ ever.

At this point, I close everything down, flue damper and all stove vents. If the weather is reasonably calm, I will find embers up to 2 days later - which can be a problem when disposing of said embers!

There is still some care required in the morning to turn embers into a roaring flame, but I like to start my days off with a bit of a challenge - it means I can indulge in deferred gratification for breakfast

Good luck.