Relative Humidity

[Safety First]

Venting into the stack will leave you with a damp (and possibly greasy & smelly) stack. The stack will not warm up enough along it's full height and the moisture from cooking will condense in it.

What I should have said..... that the heat in the extracted air, with it's moisture burden, will be lost into the huge cold space of a stack, and get dumped. If you were not careful it would end up like the garbage compactor in Star Wars; dianogas jumping all over the place!
Well, nearly.

 

[gasbanni]

Your experience of removing extractors (and without nasty surprises) I cannot contest. But a chimney open only at the bottom (vs open at both top and bottom) will be only momentarily pleased to have a kitchen extractor piped into it.
I'm not sure, but is it going to draw air when there is no cooking going on? I.e. might start to dry out a little?
I just don't think it's ideal- as in why stop there if there is a better plan? Maybe there isn't.. If it were my worst DIY problem, i'd be a happy man!

Huh ? Who saying put an extractor in a chimney that's capped ??????

 

[gasbanni]

What I should have said..... that the heat in the extracted air, with it's moisture burden, will be lost into the huge cold space of a stack, and get dumped. If you were not careful it would end up like the garbage compactor in Star Wars; dianogas jumping all over the place!
Well, nearly.

No, the house is warm. Even without an extractor warm air will naturally go up the chimney due to the pressure differential. The mass of the stack within the house will take heat from the house. So its not freezing cold. The extractor will take steam and heat from the kitchen without the problems you think might happen.

 

[gasbanni]

There is this of course, all the houses which have gas fires in use have chimneys which suffer from problems with damp due to the amount of water vapour produced in the Combustion process. Approx 9lbs of water per 100,000 btu.

This problem with damp .........sorry I've just woke up I was dreaming .........gas fires don't cause damp chimneys !!!!!

 

[Safety First]

There is this of course, all the houses which have gas fires in use have chimneys which suffer from problems with damp due to the amount of water vapour produced in the Combustion process. Approx 9lbs of water per 100,000 btu.

This problem with damp .........sorry I've just woke up I was dreaming .........gas fires don't cause damp chimneys !!!!!

You have convinced me. I was wrong.

 

[gasbanni]

You have convinced me. I was wrong.

My intention with the posts wasn't to prove you wrong. I've just got a bit of interest with chimneys and fires, solid fuel, old buildings and the like.
I find it interesting, bit sad really.

Heres one to ponder over .......if you look at an old house usually stone built if it's a gable end wall that the stacks on you can trace the exact line of the flue by following the black staining up the wall until it's near the terminal !
1. It shows to some extent that stones porous, which it's not really classed as.
2. It shows that the weak sulphuric acid fom the sulphur soot stained can travel through the brick work !
Both the points are a bit similar but who would have thought it ....its my conclusion based on observation ........never read anything on this but it stands to reason.

This all probably comes from lighting coal fires at home for the family when I was a kid so they came down to a roaring fire and bringing the buckets of coal up from the cellar and putting them at the top of the cellar steps for my mum.

 

[Safety First]

My intention with .....

No worries. I was a bit smashed last night and wrote some twaddle- elements reversed like chimney closed at top when i meant open....
Doesn't seem like a good idea to me venting cooking shmoo into chimney space, but then I have never considered (until you mentioned it) the condensation from gas appliances..... Which I remove often enough from chimneys to replace with woodburners... None of them have seemed damp... meh....

 

[gasbanni]

No worries. I was a bit smashed last night and wrote some twaddle- elements reversed like chimney closed at top when i meant open....
Doesn't seem like a good idea to me venting cooking shmoo into chimney space, but then I have never considered (until you mentioned it) the condensation from gas appliances..... Which I remove often enough from chimneys to replace with woodburners... None of them have seemed damp... meh....

It's airflow that prevents the build up of damp and providing you don't completely seal either end it's highly unlikely you'll have a problem ......think of the rain that goes down an open chimney !! Does it cause problems ? And that's water not water vapour !

 

[MICH43L]

... That's actually properly reassuring.