Roof Insulation = Advice please

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  • Well I obviously still don't understand insulation and this is causing damp problems along the edges. Our roof is made of aluminium (no leaks) there is a gap between the roof and polystyrene sheets (but only because that's how it hangs so to speak) then plywood.


    Where the wood burner flue goes through, there is roughly a foot square of space with no plywood or insulation, so straight to metal.....some mornings, there is condensation collected on this bare metal (esp when wood burner gone out and all windows shut)


    I wonder if it is this water condensation that is collecting there, running along and causing the dampness along the edges.


    This is all a learning curve, we thought we sorted it but nope so will do it again when it warms up.


    What do you do on your ceilings? what do you do around the flue? any thoughts ideas much appreciated. 3rd time lucky eh?

  • My guess, since you are sure your roof doesn't leak, is that you've got condensation (from cooking, from your breathe etc) forming on the inside face of your aluminium ceiling. You may well have the same thing happening on the walls and running down below floor level - might be worth checking this if you can, to avoid bigger problems in the future. If you search on this forum, there are several posts about condensation and how to deal/minimise it. Most relate to the use of vapour barriers, insulation, ventilation and heating. As well as sourcing opinions from others who have converted vans, I would consider phoning up a company involved in converting campers and explaining the problem, and asking their advice. Sorry I can't be of more help, but I'm sure you'll get feedback from people with more experience of this problem.

  • The walls are fine, they are made of GRP board, it's on the aluminium roof, where it obviously collects condensation because of the temperature difference. I was just wondering about sealing around the flue, in that foot square gap or even adding another sheet of ply boards to the ceiling. so it goes....aluminium, ply, insulation, ply.

  • You could insulate that gap with rockwool as its fireproof and board over with fire board I would think. Then its all insulated but no danger from the hot flue. I'm guessing though!

  • the polystyrene sheeting could be part of the problem on the rest of the roof anywhere it is not in direct contact with the inside ally roof skin condensation will form if any warm air gets to it, I prefer to use rockwool for all my insulation and pack it well.

  • any insulation with an air gap should be sealed at the edges to prevent humidity ingress. almost all insulation like rock wool work by baffling the air to prevent convection even if you rock wool the gap without sealing the cavity humid air will still get in and condense but the rock wool will hold it instead of it pooling making a large water reservoir in the ceiling.


    polystyrene and kingspan are only good if theres no gaps the reason why sprayed foam is the best is because the foam prevents conduction and convection by sealing all gaps and not allowing warm internal air to trade with cool external

  • There must be a fair amount of moisture being put into the air in your home either by damp, humans or calor gas. I'm wondering if you have a lot of gas cooking going on or a shortage of ventilation?

    Not a shred of evidence exists in favor of the idea that life is meant to be serious.

  • There must be a fair amount of moisture being put into the air in your home either by damp, humans or calor gas. I'm wondering if you have a lot of gas cooking going on or a shortage of ventilation?


    aiming at tackling the air humidity will never work because the only way to win is never go in your van and keep it under vacuum tackle dewpoints at least they have a countable number

  • 5 of us and yes we breathe, it's a big problem I know lol, any gas hob cooking done is done with window open. wood burner running which dries the air out, our humidity is generally at 15% ....it's just the roof. Will have a look at rockwall or similar then. I thought there was meant to be an air gap, maybe this is where I have got confused then.

  • ok, what do people think of vapour barriers? plastic sheeting is it a must? any pros/cons - been searching on here, not much about it really.

  • Brand name Tyvek is one of the better barriers, I used to get mine from the roofing merchants but it is expensive and you don't need a whole roll, but that is how they sell it.
    Need to be sure it covers to the edge and it overlaps.


    :beard:


    tyvek is a moisture barrier not a humudity barrier if you seal an air gap with this vapour can still get through think gore-tex for your house

  • ok, what do people think of vapour barriers? plastic sheeting is it a must? any pros/cons - been searching on here, not much about it really.


    plasic sheeting if used to seal should be contact glued with excess around any screwholes you intend to make.

  • plasic sheeting if used to seal should be contact glued with excess around any screwholes you intend to make.


    I take it that's to stop a thermal bridge? (am researching lol)


    It's just not much is said about vapour barrier and was wondering of really needed. Just seems like another layer to cause not cure condensation IYKWIM.

  • a thermal bridge is different in your situation if you stuff the cavities of your vans walls the vertical metal structures where you cant get the depth would make them a thermal bridge if you board straight over. hard to avoid but really you need to insulate EVERY metal surface.


    a vapour barrier prevents the humid air from inside the van escaping into the pockets of insulation and condensing when it finds cool metal


    the excess glue around screwholes prevents the hole you just drilled in your vapour barrier causing too much detriment

  • I have rivets in the luton that sometimes drip too, with condensation, if I glue over these, that will stop that too?


    the vapour barrier is right next to the aluminium roof yes? (alu roof>vapour barrier>insulation>plywood)

  • Should do use sticks like shit or something insulating


    Ideally an insulation envelope should be totally sealed I would pack insulation in and seal over the top as insulation stops condensation vapour barriers keep the insulation dry and control humidity

  • Basically then you are creating a softer type of insulation board, such as celotex, with the foil stuff on either side.


    We shall crack on with this when the weather gets better, ya live and learn. Gotta insulate/draft proof the cab a bit more too aswell.


    Thanks for all the hints and tips guys :D