Reducing chimney drafts from above

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Hi all,

I have a very draughty de-commissioned chimney in my Victorian house - the front room/upstairs room is freezing in winter. I’ve tried chimney balloons and more ad-hoc methods (eg bin bags full of bubble wrap) to block it from below, but the shape of the flue means they never stay in place, and it’s a right faff what with the cast iron front limiting access. So wanted to ask advise on tackling it from the other end.

The (internal) chimney stack serving both rooms was chopped off at some point to match the angle of the roof in the loft, and the roof tiled over, leaving the holes completely open under the tiles. It’s very tight to get between the joists/tiles and the remaining stack. So my options seem to be:

1) remove bricks to bring stack to level, and board over (with appropriate vents for moist air from chimney - would just sitting a board on the rough bricks create enough air gaps to achieve this ?)

2) remove just a few bricks from the high side to create enough access, and stuff in some mineral wool insulation into each of the holes

Option 2 seems a lot less effort and mess - but will it provide enough venting, or will the wool saturate and create problems? If I don’t overdo the packing, will there be enough air gaps naturally around the edges, or should I put in some sort of pipe (if so, what sort of diameter)

Any other options? Let me know if this is all too vague to answer, and I can provide pics/dimensions

Thanks!
 
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If it's not open to the outside, it doesn't need any venting. Block it up and be done with it.

Vents are only installed at the bottom when the top is still open to the outside air, as it's possible for rain and moisture to get in.
 
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Thanks for the reply. But if I block up the top, won’t moist warm air rise up from the rooms below, and have nowhere to go, and make the brickwork damp?
 
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yes, you might get salt/damp stains penetratin through the chimney breast if you completely block off the top flue openins.
have both flues swept through all fire openinsan then block off at the top but leave a v. small opening as a top vent to provide through ventilation.
i take it the dropped stack is in the bareloft not a loft conversion?

dont ever stuff newspapers or any flamable stuff up a chimney flue.
 

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