External airbricks in chimney stack - best location?

NewtoDIY

Hi,
I'm hoping some of you may have some good advice regarding the location of airbricks in a large chimney stacks. The stacks themselves reach the roof at about 13m in height and there are 2 of them in different rooms serving gas fires(coal effect) on the ground floor.

I want to prevent condensation but don't like the idea of blocked-off fireplaces on the upper levels being vented into the rooms. I know that certain DIY manuals give pictures of these with simple grills but I don't like these because they produce internal draughts.

I'd like to place airbricks externally on the chimney stacks and have the airflow circulate optimally without compromising on heat loss through internal draughts.

Does anyone know where the best place to put these bricks would be - e.g. one at the top of the stack and one somewhere around the middle?

Thanks in advance

ValHaller

https://forums.moneysavingexpert.com/discussion/4517987 may be a helpful thread.

I assume the stacks are on external walls. If they are open at the top, you just need to put a vent in at the bottom. If the stacks are closed off at the top, then there is no route for damp ingress and probably you don't need to vent?

jc808

ValHaller wrote: »

https://forums.moneysavingexpert.com/discussion/4517987 may be a helpful thread.

I assume the stacks are on external walls. If they are open at the top, you just need to put a vent in at the bottom. If the stacks are closed off at the top, then there is no route for damp ingress and probably you don't need to vent?

IIRC the cause of damp walls on breasts is condensation not water ingress so you would still need to vent

j

System

to me there seems something wrong with putting an external vent into a chimney (i.e. a massive external vent!) but maybe that's just me!
i think that putting an internal airbrick in is the easiest solution when you are filling in an old fireplace as you're doing that work anyway, knocking a hole into the outside of a chimney is obviously extra work and gives the potential for further water ingress to the stack - although as said having a low level external vent on the chimney might be enough

NewtoDIY

Thanks for the replies. The stacks are open at the top and as we're having some building work done soon, scaffolding will allow access to the stacks higher up.
I'm totally against internal grills for blocked-off fireplaces. There is a noticeable draught which comes from all of the ones we currently have and this seems to defeat the purpose of making a room warm. I feel that allowing air circulation to the outside is the best way of preventing condensation to these (now) redundant stacks.

Do you think it is possible to have too many airbricks? I'm thinking one at top and one just above the reverse side of the blocked-off fireplace.