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Is interstitial condensation a problem?

SuperHomes Revamp Forums General Discussion Is interstitial condensation a problem?

This topic contains 3 replies, has 4 voices, and was last updated by  GrahamW 7 years, 5 months ago.

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    The SuperHomes website now has a couple of items about interstitial condensation and it seems like a subject ripe for discussion on this Forum…

    Is anyone else out there monitoring pre/post insulated walls to see if this is a concern?
    Has anyone come across a serious case of it either in their own home or elsewhere?
    If so, how did you identify it, what were the symptoms, what was the cause, how did you stop it?
    If you’ve insulated your walls, were any precautions necessary to avoid it? If so, what did you put in place?

    If you’ve got any information from your own personal experience to bring to this subject it would be great to hear from you. Did you experience rot or mould after installing internal wall insulation that could be attributable to interstitial condensation?



    The first wall we had insulated, about 1984 or 85, was done by a small builder with absolutely no attempt to stop warm moist inside air from getting behind the insulation. At the time I did not realise the imortance of this. It used insulated plasterboard mounted on battens screwed directly onto the wall; at least the battens used were pressure treated with preservative. And it was in the bathroom, where humidity is sometimes very high.  About 25 years later we completely remodelled the bathroom and took the opportunity to rip out the old insulation and put in much better insulation with a proper vapour barrier and internal, warm side, battens.

    I expected to find a pile of rot behind the plasterboard, but it was OK. I think the explanation is partly the pressure treated battens, but also the poor standard of insulation (18mm of polystyrene!!) meant that the wall behind was still fairly warm.  The better your insulation, the colder the wall behind will be, so the more important to seal the insulation really well.



    Condensation is a much discussed and not necessarily understood subject. But we know of no interstitial condensation problems if internal insulation work is properly carried out and in some instances measurement of damp in timber beam ends with internal insulation installed , show reduced moisture content over time. Research and monitoring is ongoing. Some people think breathable insulation is best but I prefer installing a good vapour barrier with internal insulation to stop the moisture tracking across to the original wall in the first place. I think wall dampness is often associated with rising damp and penetration from outside, and often this is kept in balance by subsequent drying off to the outside.



    I’m interested in installing moisture sensors behind the wall insulation I’m currently installing, with vapour barrier integrated in the PIR sheets.

    I see that some Superhomes have installed just such sensors. Can anyone recommend a guide to setting up these sensors or perhaps recommend a particular sensor for this purpose.


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