Condensation Issue

[forrejam]

Hi all, looking for some advice. I have noticed with the colder weather coming in Scotland that I have a huge amount of condesation forming between the plastic roof skin and the outer skin of the motorhome. So much so that it's building up and dripping down through my ceiling speakers as that's the lowest point within the roof. I've checked for leaks and the van roof is sold and all seals intact so can only put it down to condensation. The vans not in use and I do not heat it whist not in use so was surprised to see so much condensation. I'm thinking of filling the entire open space with some kind of insolation such as expanding foam or something similar used in cavity wall insolation in houses so that the space is completed filled. Would this be recommended or is there anything else I can do to reduce the build up of water in this area. I am currently running a dehumidifier which has dome away with the condensation but that cant surely be the answer longer term? Any advise would be greatly appreciated. I have shown some images where I managed to put my phone in the ceiling speaker hole to show the issue.

 

[Insider]

Have you tried some form of ventilation? Perhaps two windows cracked open a tiny amount. I am surprised you have condensation in there with it unoccupied.

 

[68c]

There must be moisture within the van for condensation to form on the cold roof structure. Assuming no leaks and no wet towels etc in the van it must come from outside air entering the van through vents, poor door fit etc.
First make sure the dashboard air control is set to recirculate to lessen damp air coming in through the heater matrix.
Then look at all the doors and temporarily tape up any vents.
Finally remove as many cloth items as you can; bedding, cushions, clothes floor mats etc.
Good luck.

 

[forrejam]

I have not tried that as I didn't think the ventilation would flow into that space given that it's above the roof line. Will certainly give it a try though. Very strange to get that amount of build up which is why I'm thinking of filling the space above with insulation.

thanks

 

[Littlewheels]

As stated vent the MH and spread newspaper around the MH generously.
The newspaper will attract and absorb moister and dry out in a continuous cycle. Do attempt to soak up and air the MH before starting the cycle….it works.

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[royandsharont]

My Bessacarr had a front roof top storage cupboard above the cab seats made up of a plastic full one piece moulding. I noticed condensation dripping down in that area once. The dealer said Swift had not filled the cavity with any insulation so they put some in and it never happened again.

 

[donkey]

I had the same issue on a Swift Bolero, they had not insulated the space. You need to prevent warm damp air getting in contact with the external roof panel. Just filling the void may not work effectively. I firstly used a self adhesive insulation stuck to the roof panel, this prevented any air coming in contact with the cold surface. This was followed by filling the void with Rockwool or similar. Never had any problems after that.

Geoff

 

[Puddleduck]

Could you use a dehumidifier in there?

We use one when parked up (on the drive). I know it pulls in cold air from outside but I think that is good for air circulation anyway.

 

[Bramidan]

Let’s get technical, condensation is the effect of moisture laden air ( remember warm air has the ability to hold more moisture than colder air) hitting a colder surface, so the moisture laden warmer air gets cold, cannot then hold as much moisture and condensation forms on the cold bridge.
So there are recognised cures, reduce the amount of moisture being held in the warm air, how? don’t introduce the moisture into the air ( doesn’t sound relevant in the circumstances of the OP’s post)
Reduce the amount of moisture in the air, dehumidifier. Won’t need a huge one for the cubic area of a Moho but of course need a power supply.
Increase the amount of ventilation in the Moho, this effectively reduces the amount of moisture in the encapsulated air, go back to your O level physics!
Try to get rid of the “cold bridge” and that is where the insulation comes into play, remember though if the air is moisture laden you will get condensation elsewhere, where warm air humid laden air meets something which causes a drop in temperature, the colder air can’t hold as much moisture.
We all know the benefits of an insulated screen in a Moho to reduce condensation on the internal surface of your windscreen.
I guess you need to try all methods, start with the cheapest first! Increase ventilation.
Second, fill ice cream containers up with salt to absorb the moisture, when rock hard put the salt back in the sun.
The newspaper tip does the same thing.
Third, In your climate, invest in the dehumidifer.

 

[pappajohn]

Can't really tell from your pictures but you mean there's no insulation at all above the roof lining?
I wouldn't advise expanding foam as it does expand with some pressure and could cause bellowing of the roof lining.
I would consider, as a winter job, taking down as much lining as possible and putting loft insulation in and then refitting the lining

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