Insulating behind wardrobes?

[Stuart]

We need to replace the old built in wardrobes. These are on an external wall/corner and have shown signs of condensation and mould and clothing has been damaged. We have cavity wall insulation and the external wall was recently repointed (there have been damp issues on the same wall in the adjacent room now addressed).

The same wall is the obvious location for replacements as relocating to an internal wall would be difficult. I don't want to go to the expense and hassle only to have a repeat of the condensation/mould issue so my bright spark moment was to fully insulate the wall with 25mm celotex (other PIR boards are available!) and then plasterboard and maybe skim or just decorate the plasterboard as most of it will be covered by the wardrobes.

I then thought can I just use celotex behind the wardrobes (they won't be full height). This would save me a lot of agro and some cost and a whole 12mm of space!

However, for some reason I'm not convinced this is the answer to the problem (overthinking again) so was wondering if the collective knowledge on here has anything that may help with my deliberations.

PS - freestanding wardrobes ruled out.

 

[9fingers]

I dont see why not. The problem is cause by allow warm moisture laden air contacting a cold wall which insulation will prevent. However be certain that none of problem is caused by penetrating moisture

The space above should have sufficient ventilation unless you pile up stuff on top in which case the insulation should be full height.

 

[AndyP]

I had a similar problem years ago solved not by 25 mm Celotax but by polystyrene insulation on a roll, probably only 3mm thick. I would welcome more educated opinions on this before you try as we did not stay in the house long afterwards to see the long term effect.

 

[SamQ aka Ah! Q!]

Stuart, Celotex comes in a plaster-board-faced variety. I used it extensively on 9" solid walls, with marked condensation problems on their internal faces. Result! I can most thorughly recommend it as a prophylactic measure.

N.B. When I installed wardrobes in the rooms thus treated, I was still mindful to leave an air-gap between the wardrobe back and the plasterboard face: about 2.5-4.0cm, from memory. This allowed circulation, and, with 50mm Celotex beyond that again, condensation was prevented.

 

[Stuart]

Thanks for the comments.

I had a similar problem years ago solved not by 25 mm Celotax but by polystyrene insulation on a roll, probably only 3mm thick. I would welcome more educated opinions on this before you try as we did not stay in the house long afterwards to see the long term effect.

Andy, I believe this wall has that insulated wallpaper on it already so it clearly hasn't worked although to be fair the work we had done removing the crud and damp fibre insulation in the cavity won't have helped.

Stuart, Celotex comes in a plaster-board-faced variety. I used it extensively on 9" solid walls, with marked condensation problems on their internal faces. Result! I can most thorughly recommend it as a prophylactic measure.

N.B. When I installed wardrobes in the rooms thus treated, I was still mindful to leave an air-gap between the wardrobe back and the plasterboard face: about 2.5-4.0cm, from memory. This allowed circulation, and, with 50mm Celotex beyond that again, condensation was prevented.

Sam, yes I'm aware of the insulated plasterboard (used it in our extension) but it's currently hellish expensive and for a small wall like this it's cheaper to use separates. Space isn't going to allow that sort of gap behind but I'm mindful to leave a small gap to help ventilation.

 

[9fingers]

Did you cure the source of the damp fibre insulation? if not that should be a first step really

Bob

 

[Mike G]

Thanks for the comments.

Andy, I believe this wall has that insulated wallpaper on it already so it clearly hasn't worked although to be fair the work we had done removing the crud and damp fibre insulation in the cavity won't have helped.


Sam, yes I'm aware of the insulated plasterboard (used it in our extension) but it's currently hellish expensive and for a small wall like this it's cheaper to use separates. Space isn't going to allow that sort of gap behind but I'm mindful to leave a small gap to help ventilation.

Stuart, if you leave a gap you may as well not bother with the insulation. All you would be achieving is visually hiding the mould. In fact, this is what I think you'll be doing anyway, even if you don't leave a gap. In your intial scheme the plaster behind the insulation would be even cooler than it is now, as it would be sheltered from the rooms heating. Along with the reduction in air movement that comes with putting a board against the wall, this increases the chance of condensation occuring and mould growing. The fact is that you won't see that mould until you strip the insulation board off in years to come.

To prevent mould growth you need to increase the temperature of that wall surface, and you need to increase ventilation. You'll achieve neither of these by applying anything to the inside of the wall.

 

[Stuart]

Did you cure the source of the damp fibre insulation? if not that should be a first step really

Bob

Yes Bob, the repointing was the major issue. That and the application of masonry cream appears to have cured it.

Stuart, if you leave a gap you may as well not bother with the insulation. All you would be achieving is visually hiding the mould. In fact, this is what I think you'll be doing anyway, even if you don't leave a gap. In your intial scheme the plaster behind the insulation would be even cooler than it is now, as it would be sheltered from the rooms heating. Along with the reduction in air movement that comes with putting a board against the wall, this increases the chance of condensation occuring and mould growing. The fact is that you won't see that mould until you strip the insulation board off in years to come.

To prevent mould growth you need to increase the temperature of that wall surface, and you need to increase ventilation. You'll achieve neither of these by applying anything to the inside of the wall.

Thanks for your thoughts Mike. There's no way given current layout I can increase the temperature of that wall apart from leaving the wardrobe doors open and you can guess my wife's thoughts on that.

Would leaving an air gap (of say 25mm) behind help? This is achievable reasonably easily together with some improvements in ventilation.

We're actually considering one of the Ikea solutions which would mean sliding doors (in themselves 'gappy' to help ventilation) together with a racking system screwed straight to that wall so that would also aid a temperature increase.

I'm quite keen to get this as right as I can as I can't afford to do this again!

 

[Mike G]

Would leaving an air gap (of say 25mm) behind help? This is achievable reasonably easily together with some improvements in ventilation.

Yes, it would. if you can leave it open at the sides and plinth, too, that would be a help.

 

[laynainx737]

I had the same issue behind a wardrobe and initially made the mistake of pushing it too close to the wall. We started getting condensation, so leaving a gap for airflow made a noticeable difference.