Draught proofing a chimney breast with loft insulation boards?

[Sharpey]

Hello all.

I have a front room with two open chimney breasts. I am concerned these are making the rooms really cold. Also, I am going to be using a dehumidifier in these rooms so I want to minimise the amount of the external air being pumped in to the room.

To block them, I was thinking of getting some Celotex board, cutting it to size, and laying it flat horizontally in the chimney (it has internal bricks either side that can support the boards). I could leave the back edge slightly shorter to allow some ventilation or just cut a hole in the middle of the board.

In theory this should greatly reduce the amount of draughts whilst still allowing the chimney to breathe. Is this a good idea or does anyone see potential shortcomings in this method? Will a Celotex board provide adequate insulation?

I am reluctant to go for chimney balloons as they are expensive and have mixed reviews.

I should add, both chimneys are unused and won't have any fires being lit.

 

[foxhole]

You can use any board, non will provide insulation, just reduce air flow.
Is £12 expensive for a balloon? you could use a lump of rigid rockwool stays put without a shelf.

 

[Sharpey]

Hi foxhole, thanks for replying.

The chimney balloon that fits my chimney is £25, I need two. It has some terrible reviews, so I don't really fancy paying £50 for something that might not even work. I think it's another £11/12 for the pump to inflate it as well.

I don't mind what type of insulation used if there is not a huge difference between them as most should be easy enough to lodge in there. But in theory is the principle OK, as in draughts will be reduced, room will become warmer?

 

[chappers]

use a chimney sheep rather than a balloon , they don't need inflating. and also allow a bit of airflow still

 

[foxhole]

Why are you needing a dehumidifier, ventilation is free.

 

[Sharpey]

I need a dehumidifier because the internal walls are suffering from damp. It's not penetrating damp. It's been like this for two years and nothing seems to fix it, opening windows or anything, in fact it seems to get worse.

use a chimney sheep rather than a balloon , they don't need inflating. and also allow a bit of airflow still

This will set me back around £100 for what I need so I'm going to pass on them.

 

[foxhole]

If having an open chimney does not dry out a wall over two years then it's far beyond a humidifiers capacity.
You need to cure the damp source, what makes you so sure it's not penetrating damp?

A few pics might help identify the problem.

 

[Sharpey]

They're internal walls, so I don't think it is penetrating. The moisture didn't start at the bottom so it's not rising (assuming that even exists because it is disputed)

The dehumidifier does seem to be improving matters.

I think it is a combination of salts in the wall and internal excess moisture, and cold spots on the wall, all creating a perfect storm. It seems to have happened after the place was replastered. Prior to that it was lining paper on the walls and this might have provided some insulation as the damp didn't appear in the same spots then.

I posted a thread on it a while back with pics, consensus was to leave it and see how we got on but it never got better after leaving it, it got worse

//www.diynot.com/diy/threads/weird-internal-damp-problem.392663/#post-3025550

 

[foxhole]

The walls are adjacent the external wall and window which could have voids around it allowing in moisture, I see you had a damp proof company in [never a good idea] seems they have made things worse by not identifying the source and then making it worse with there work.Salts are washed thru the brickwork so you still have penetrating damp.You also mention a porch in OP so may have poor roof covering/finish letting in rain.

 

[Sharpey]

Thanks for the advice. The porch is closed off, it has two front doors. The damp in the hallway is on the internal door side. As for the living room, the damp wall isn't directly next to the window and I just don't see where from the window there can be a penetration of sufficient water that somehow migrates to a wall a foot away. There are no cracks or anything on the wall directly outside.

Pretty much that entire bottom foot of plaster was hacked off by the damp company and replaced with their damp proof plaster or whatever. The right hand side underneath the window was the where the original damp was, that has now gone and you can see the new spots developing. Perhaps whatever the original source of the damp was still exists, is avoiding the special plaster and migrating upwards and settling above like in the pictures?

 

[foxhole]

Difficult to defy gravity, tends to fall thru the structure from above.