Another Mould Problem

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Sheffield
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Hello all,

I'm afraid I'm going to be another DIYer posting a question on mould/damp/condensation problems and asking for advice on a fix.

I have a first floor storage cupboard in a bedroom above the stairs which has been 'converted' into a wardrobe. The cupboard is about 1m square, brick walls - two internal walls and one external wall (the door taking up most of the fourth wall). There are central heating pipes running under the cupboard, no carpet. There is also a loft hatch in the cupboard. The property was built in 1909 and has recently had cavity wall insulation put in.

Here's the problem (which you've probably already guessed): There is mould growing on the clothes that were against the external wall. I assume that there are a number of issues causing this - heat from central heating pipes, cold air from the loft hatch, cold external walls. I assume that these mean that condensation forms and then the proximity of the clothes causes mould to grow.

Here's a few things I was thinking of doing:
Insulate the loft hatch - the loft has been re-insulated but don't recall we did the hatch.
Leave the cupboard door open during the day to allow better circulation of air.
Put in a 'false wall' - a plasterboard/plywood wall with, say, 1cm gap from the exterior wall. Would something such as kingspan be better?
Not use it as a wardrobe as the problem would still persist.

The above suggestions may be idiotic, so before I start making big mistakes I'd appreciate any comments or suggestions.

Many thanks

David
 
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To control condensation you must control relative humidity. The way you do that is by stabilising temperature of the room and surfaces as much as possible and by minimising or balancing the amount of water vapour in the air. First of all identify any surfaces that are significantly colder than others - i.e. cold areas of wall, floor, ceiling etc. Where possible insulate those areas. The aim is to try and even out the temperature so you have the minimum temperature difference between different surfaces at any time. The worse case is a cold wall in an enclosed space - that's the perfect recipe for condensation and mould. Minimising water vapour is simple; don't dry clothes on radiators and don't have excessive house plants. Balancing water vapour means ventilation. Ventilation will dilute the amount of vapour in the air. Open windows occasionally, or at least open trickle vents, and use extractor fans in the kitchen and bathroom.
 
Thanks John,

In terms of the cold surfaces, I can certainly sort out the loft hatch as it's a 'secondary' hatch for the loft so wouldn't be a problem to lay insulation over it.

Regarding the exterior wall, I've seen a few threads mentioning Warmaline as helping to bring the temperature of the internal side of the wall up. At £5 a roll for 914mm x 600mm it wouldn't be too expensive to do the cupboard out with it. Reviews suggest that it raises the temperature of the wall enough so that condensation will not form. although it doesn't remove the potential for moist air in general.

Hopefully a combination of the two, and leaving the cupboard door open will help.
 
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Any insulation on the cold surface will help, but obviously the more the better. I'm not familiar with warmaline but it's probably the same as wallrock which I do know. Maybe put a couple of layers on. The airborne condensation occurs because RH increases when temperature drops. So if you have fairly high RH to start with the temp doesn't need to drop much for RH to reach 100% - i.e. condense. We produce a lot of vapour at night just due to breathing. When the heating goes off the temp drops and to avoid condensation you need to dilute that vapour with some form of air movement or ventilation. On the coldest nights it may be worth keeping the heating on low.
 

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