Condensation.

[rottenjaw]

Hello, Im new to this forum. I am converting an LDV Maxus into a camper and have a problem with condensation. I Put battens on the roof of the van, then tri iso insulation then 6mm ply. (So there is an air gap). Iv'e not finished the sides of the van yet, so the ceiling is not sealed and there is a gap all round the edge of the ceiling. Today I put my hand up and felt the metal roof is wet. Will the condensation stop when i have sealed the ceiling? Any ideas or suggestions will be much appreciated.

Thanks, David

 

[hextal]

from what I can gather it is best to have no gap between the panel and insulation. If there is a large gap - even if it is sealed from the living space I believe that it is possible to experience interstitial condensation, where the moisture in the air in the space condenses.

This gives a problem if using a radiant barrier rather than an insulation barrier, as the former requires an air gap (not sure what type you have used).

The above is basically just a regurgitation of what i've read in a number of other places, so I wouldn't just take my word for it..

 

[sparrks]

I should imagine that insulating a van and adding a vapour barrier and sealing it all up is not a good idea at this time of year - lots of moist air being trapped between the vapour barrier and the panelling. I did mine on a hot dry day with no moisture in the air. I appreciate these things have to be done, but maybe some precautions could be required.

 

[n brown]

condensation occurs when moist air hits a cold surface,so presumably,if all the metal had carpet,or thin foam like camping mats or even old velvet curtains stuck to it,problem solved.then more insulation can be added as needed. i have only actually done this in the locker over the cab with up holstery material and that works fine

 

[rottenjaw]

Thanks for the info. I took everything down and started again! I stuck 25mm Celotex directly to the metal roof, then I put the Tri Iso and plywood back up and sealed it. Hopefully I have cured the problem. I seem to be doing everything twice!

 

[Hymer494]

Condensation

Insulation is the first resort, VENTILATION is the second . Even my Hymer gets condensation if I do not have adequate ventilation.

 

[Chris K5]

The insulation should be fitted tight to the steel bodywork of the van, if there is a gap between insulation and roof/walls of the van this is where you will get the condensation.
Also from experience don't use TriIso quilt, it's rubbish. You would be better using celotex or Xtratherm insulation.

 

[jamesmarshall]

A good vapour barrier will allow heat loss (you will never stop heat loss though with good insulation you can slow it down) whilst keeping the moist air within the habitation area. This moist air then needs to be ventilated from the van. a decent heating system will maintain comfort levels despite the continuing air changes. If you simply "cabin up" and don't allow for the air cahnges you will eventually get dampness and possible mildew. This is not such a problem during the summer months.

 

[coolasluck]

I used low-e foil insulation,with aluminium facings on both sides,best insulation on the market(i will let you know on that one) this reflects the heat in and kepps it out in hot climes.

 

[coolasluck]

There is a lot of crap on the market like bubble wrap with shiny foil,i wouldnt even bother with that,i have also had to do things twice and that was because i found the low-e product so decided to buy and use on my coach.

 

[ellisboy]

Thanks for the info. I took everything down and started again! I stuck 25mm Celotex directly to the metal roof, then I put the Tri Iso and plywood back up and sealed it. Hopefully I have cured the problem. I seem to be doing everything twice!

You don't need a vapour barrier with celotex,so what you've done is fine.What sort of ventilation do you have? Roof lights / windows etc.We always leave the smallest rooflight ( bathroom) open a crack all the time.