Sealing a capped flue without any airbricks

[BrainStrain]

Hi, first time post but in need of help!

We have an old chimney flue which leads down into our kitchen right above the cooker. Small bits of debris fall down it occasionally so we want to seal it off (or at least stop the debris falling into our food!).

Spoke to a builder about it and he's suggested sealing it off at the bottom, above the cooker. As the flue is capped at the top (but not sealed) he reckons that will be enough ventilation and there's no need to fit any airbricks at the bottom (in the kitchen, which admittedly will be generating warm moist air).

By question is whether this is OK? I'm concerned that one opening at the top of the chimeny might not be enough to ventilate the whole thing. Is it OK to seal the flue and just leave an opening at the top?

 

[Alastairreid]

answer..........no you will have to maintain an airflow, vented both top and bottom............seal off above your cooker and put vent above if you have the room.

 

[Richard C]

I'm concerned that one opening at the top of the chimeny might not be enough to ventilate the whole thing.

You’ve answered your own question really; you are right to be concerned, do as alistairried suggests.

 

[Helg]

22 years ago I renovated a detached 1930s house. All the chimneys are blocked on top and also where the fireplaces were. Probably not ideal, and from time to time I worry, but so far no prob. One roofer even said I should not worry. Question: how dangerous can it be? Can I just open the top (fireplaces would create major upheaval, nice wallpaper etc would be damaged)

 

[Alastairreid]

hi, wouldnt say dangerous!!! more "dampness" the inside of your chimney stack will be sodden.
even more so if the flue is on an outside wall.
anyway must maintain airflow to to keep vent dry.

you could fit wall vents without causing any damage if you were carefull.

 

[Helg]

Tks for reply, silly question, if it is airtight, how does it get sodden?
At moment there is NO air flue/vent/cap whatsoever, could I put one vent on outside wall? and cap on top?

 

[Alastairreid]

yes a vented cap on your chimneyhead and a brick vent on the outside would give you the required air circulaton.
far easier putting on inside though!.

your chimneyhead is always absorbing water and with no heat or air circulation to expel it,dampness will eventually start appearing.

 

[Richard C]

hi, wouldnt say dangerous!!! more "dampness" the inside of your chimney stack will be sodden.
even more so if the flue is on an outside wall.
anyway must maintain airflow to to keep vent dry.

you could fit wall vents without causing any damage if you were carefull.

That’s it exactly

 

[Richard C]

yes a vented cap on your chimneyhead and a brick vent on the outside would give you the required air circulaton.
far easier putting on inside though!.

your chimneyhead is always absorbing water and with no heat or air circulation to expel it,dampness will eventually start appearing.

& that's it even more exactly!

 

[PERMANENTP]

I want to cap my redundant chimneys and all advice seems to say that if this is done then there should be ventilation from top to bottom. This incurs a large loss of heat from the house. How about breaking into the chimney breast in the attic and plugging the flue above bedroom level with insulation material and leaving an air brick above the insulation level and capping the chimney at the top with ventilation there too. This maintains heat inside the house and allows circulation in the cold upper regions of the chimney, thus avoiding damp. There should be no damp problem below this level as the rooms will all be heated to a similar degree.