Is there a mention of insulation dewpoint condensation in the wiki?
I looked at:
I remember seeing ascii art of it sometime ago, i think on this newsgroup.
If you put fiberglass on your loft floor, and cover it with a vapour barrier on the cold side, then warm moist air will travel up, cool down, and condense giving water which will spoil the insulation and rot wood, if i understand it correctly. [g]
Indeed. I've contemplated writing a 'Vapour barrier' article but haven't done so. Would you like to write something?
I've no idea whether you're wiki experienced or not, but if you want its not a problem for one of us to move soemthing you write from here to there if you give permission.
NT
It's usually not a problem unless you have something forming a vapour barrier on the cold side of the insulation, such as a floor or sheets of something over the insulation in your loft, which prevents the cold side ventilation.
I have put kingspan over rockwool insulation in my loft so I do have potential condensation!
i think it's worst when theres an air current leaking through, that could drop large amounts of dew.
But in my case over time through brownian motion there could be condensation in the rockwool.
I still havnt found the ascii art someone poosted here a year or two back, I hope I saved it somewhere, I lost my archives oncxe upon an 'upgrade'.
[g]
Was this it?
Mathew
Is Clive that wrote this still around?
yes, (though my thunderbird is showing it in a proportional font!) [g]
It's not ideal. Chances are the kingspan is doing the majority of the insulating as it's a much better insulator (although depends on relative thicknesses too), and it may be that the bottom of the kingspan which is forming a vapour barrier is rarely below the dew point. It would have been better to roll up the rockwool, and re-lay it over the top of the kingspan if it was reusable, or seal the back of the ceiling and then put the rockwool back where it was. It might be a good idea to lift one of the pieces of kingspan over the most humid room (a shower, or kitchen) at the end of the winter, just to check the rockwool is dry underneath. Also, make sure all holes through the ceiling (pipes, cables) are reasonably well sealed. Avoid fitting recessed downlights or anything else which punctures large holes in the ceiling.
Air from above the insulation is colder and will have already dropped its dew somewhere else. Circulation of this is more likely to dry out the insulation (albeit reducing the effectiveness of the insulation). It's the warm air from inside the house which drops dew into the colder insulation.
presumably it's clive's copyright, Clive snipped-for-privacy@jumbojet.uk (drop the elephant to reply) it says in google groups... is clive still around or has anybody got his email adrs to ask for permission please? [g]
If Clive doesnt surface its legal to use it by rewriting it, same material but altered wording all through.
NT
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