Mouldy walls

[JohnReeves]

Hello
I have a bungalow, the front of which is north facing, my problem is with the main bedroom which has 3 outside walls it gets very cold in the winter even with the radiator on full blast. I have had cavity wall insulation which to be honest did not make a lot of difference. But the main problem is with the walls, if we put up say a wardrobe against one wall after 2-3 weeks we start to get black mould behind it. How can I stop this please!!!

 

[jeds]

The first thing is to look at the sources of water vapour. If you have a large number of indoor plants you might have to consider removing some. Do you hang washing on radiators? if so don't. If you tumble dry make sure the machine is well ventilated to open air. Any other sources of vapour or dampness in the house? Check all possible sources and reduce.

Secondly you need to consider ventilation. Do you have extract fans in your kitchen and bathroom? Are they linked to the light switch and set to over-run? Are they switched on? Do you have trickle vents on your windows?

Thirdly insulation. Cavity wall insulation is normally quite effective so if the wall is still very cold then you might be worth confirming full coverage and that it has been injected properly. For certain problem walls I sometimes specify a thermal lining. I have found that to be very effective in the right situation.

Generally; condensation is a buy off between temperature, ventilation and the amount of vapour present. It's a matter of getting the balance right.

 

[JohnReeves]

Hello Jeds
Many thanks for your reply. The room is a bedroom so no water vapour present and we do have a trickle vent on the window which we keep open. The walls still seem cold after cavity insulation so i will check that it has been done correctly.
Can you expain what thermal lining is?. I am thinking of using the foil backed plasterboard and fixing it the the wall with batons and maybe rockwool between batons. what do you think?

Thanks for your help so far.

 

[^woody^]

Read these forums and the wiki for general condensation prevention advice. If you are already taking all the precautions, or some measures are impractical, then it may be that the issue will not be treatable via normal means

Some properties are more susceptible to condensation mould issues, and despite heating, ventilating and insulating, the problem remains

In these cases, consider a positive pressure fan unit which are successful in dealing with extreme mould problems. There is a long thread on here somewhere search for " lofty " or google

 

[JohnD]

//www.diynot.com/wiki/building:condensation_in_houses

Please answer Jed's question:
"Do you hang washing on radiators"

 

[JohnReeves]

Thanks for all the advice
No the bedroom is a spare room, unoccupied most of the time and we don't put washing on the rads.

Will read the wiki as suggested....not sure what to do next

Cheers

 

[alittlerespect]

You will probably find that the central heating system was never designed to cope with a room with 3 exposed walls, especially when the room is north facing.

Filling a cavity with insulation material can sometimes cause as many problems as it cures, and it is definitely not a 'cure all' solution. Although there should have been some improvement it is likely that the north facing aspect of the room and 3 exposed walls means that the room exposure to thermal bridging would be severe to extremely severe in winter.

The room being unoccupied doesn't really help the situation as the fabric of the room will be colder than other parts of the bungalow. You have 2 problems - firstly you have warm air diffusing into the bedroom and meeting a cold surface which is causing surface, and maybe interstitial condensation to occur, secondly by putting furniture in front of the wall you are restricting the air movement which is not giving enough air changes to remove the surface condensation both of these events are possibly conspiring against you to cause the mould growth.

The only real solution to your problem would be to clad the external walls within the room with a insulated plasterboard (foil backed won't really help as you have limited radiant heat available to save). British Gypsum and other manufacturer's do a PIR (insulated) backed plasterboard, and if you can stretch to using around an 80mm thickness board (which can be stuck on the walls), this should give you a noticeable improvement, but you will still need to provide some background heating, best bet stick a TRV valve on the radiators.

With the additional insulation the room should also be affordable to heat, which will get rid of your mould problem. PIR board is also vapour resistant so you do not need to worry about a vapour proof barrier to avoid condensation between the insulation and the wall.
Letting the room get cold while the rest of the bungalow is warm is a recipe for disaster - final comment - you may also want to consider increasing the insulation within the loft.

Regards