Mould growth behind fitted wardrobe

[markwm]

Just removed a wardrobe that was fitted in a chimney recess on an external wall. It was fitted flush up to the wall.

There was some mould growth on the rear of the wardrobe. The hardboard backing wasn't nailed brilliantly and there was some gaps around the perimeter.

Am I right in thinking the reason there is mould is because warm hair has gotten into the wardrobe, when the doors are opened etc and found it's way on the cold surface behind?? As the wardrobe is fitted flush there's no ventilation at all behind there.

Question, why would the mould only grow on the hardboard back and not on the wall? I would assume the wall is colder than the hardboard. There was no mould on the wall.

I need to refit the wardrobe. Plan is to insulate behind the wardrobe with 25mm kingspan and then seal up any gaps in the back of the wardrobe with acoustic sealant.

 

[JohnD]

the problem you describe is very characteristic of condensation. The airflow behind furniture is insufficient to keep that part of wall as warm as the rest of the room, but enough to allow warm damp air to circulate.

Ventilation will help, sealing the void will make it worse.

Increase ventilation to reduce the humidity, use extractor fans in bathroom and kitchen, do not leave wet washing or damp towels around, read //www.diynot.com/wiki/building:condensation_in_houses

 

[noseall]

The peculiarities of condensation related mould growth will never be fully understood!

But yes, you are on the right track and seem to have it sussed. Short of introducing ventillation behind the wardrobe that is...

 

[markwm]

I understand ventilation is the reason mould is growing. But unless someone can explain how it's possible to provide adequate ventilation *behind* a fitted wardrobe without having it a foot off the wall then the obvious solution to me seems to be to stop warm air getting to the cold area. (ie, the wall)

I would ideally like ventilation but really don't know how so sealing the wardrobe with sealant and a vapour barrier to prevent moist warm air seeping through to the cold wall as well as insulating the wall is the best I can come up with.

 

[ajrobb]

I have suffered too much mildew INSIDE built-in wardrobes ever to consider putting them against outside walls, at least without heating. Keeping the doors open during the day helps dry out condensation but doesn't look good!

The reason for condensation is not because it is too warm behind the wardrobe but because it is too cold (below the dew point). It is common to leave a 50mm ventilation gap in roofs. A 50mm ventilated gap behind the wardrobe with open vents at top and bottom should allow the gap to warm up above dew point.

Now I shall get on my creaking hobby horse and risk embarrassment - I'll suggest the alternative of a sealed reflective cavity:

If you can seal battens (at least 19mm deep) around the edges of the recess (including top and bottom), you can cover the recess on top of the battens with an impermeable, low-emissivity foil like Reflectatherm. Stick the foil to the battens with tape. This gives you a sealed reflective cavity at least 19mm deep in front of the plaster, which provides some insulation. Proctor Group quote an R-value of 0.644, which is as good as 25mm of mineral wool or 15mm Kingspan. For a solid brick wall, it cuts out two-thirds of the heat loss.

You can then build your wardrobe in front of the foil and not worry about condensation damaging the wall, because that's taken care of by the foil. However, I would recommend you include ventilation at the top and bottom of the wardrobe into the room to keep it near room temperature. This should prevent mildew.

 

[tfish]

a air brick or plastic air vent would solve the problem if make a draught.

iv come to reaslise u cant have your cake and eat it when it comes to condensation