Winter condensation!

Phantom

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It's been our first winter full-timing in our motorhome and it has highlighted a few areas where further insulation was required to prevent condensation which if left would have lead to mould growth too. As we're on electric hook up we are barely using the gas blown heating which would have maybe alleviated some of the issues to some extent but improvements were still needed.
Placing a sheet of 1" polystyrene on the plywood bed base has made up for the cold garage below causing minor condensation. The issue was much worse where the gas locker protrudes under a bench seat but again snug fitting 1" polystyrene resolved that too.
As to be expected really the Sprinter metal cab area is uninsulated apart from the roof and perhaps floor covering if that counts. But there are two remaining areas where I'd like to make improvements. The main one is to somehow insulate the footwells to prevent condensation forming there daily which runs down under the flooring to remain trapped and potentially rot the floor. I removed the factory fitted plastic/foam flooring and the entire floor was soaking wet. Even though the metal floor has bitumen like sheeting bonded to most of it there was signs of mild rust in one area. I guess that many campervans and motorhomes also have this issue in winter but it just goes unnoticed? Condensation also forms on the inner door skins which would have also gone unnoticed if it weren't for the storage compartments which revealed it.
So I guess that the solution to all is to bond some form of flexible snug fitting insulation to those internal areas? Any ideas?
 

Nesting Zombie

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Hi ya,
VENTILATION & Movement of air in general is the key in my experience !.
Slays are better under the mattress & Cushions than Board.
Leave Dash vent on Open To Outside to help with Cab windows. Crack open Rooftop Vent, make sure Floor is vented as well I know I know it’s a wonder how the Blinking hell you get the area warm isn’t it, But it’s about ‘Balance’
14AD42B4-3C62-480B-9106-7F4C4C1AFAF0.jpeg

Don’t know if you can make it out, but I’ve actually got a Floor vent in my Garage Locker Under the bed, Then Slats Under my Mattress that allows free air movement
 
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colinm

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AS NZ has posted, getting air circulating is a good idea, and as you yourselves have noted not having the blown air running makes some areas worse.
My concern with what you've done, polystyrene is not vapour tight, so whilst it may have slowed vapour transfer down into garage it won't have stopped it, this is why if speccing a van again I'd bit the bullet and have the electric element combi.
When we use electric heater in van we put it in the cab area, my hope being it keeps that area warm and stops condensation.
For the doors, you need to stick on closed cell insulation, if you google it you should get results
 

Tookey

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I have to agree with NZ, it really sounds like you are lacking ventilation so are not addressing the cause

Froli might be more suitable for your bed base

 
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Phantom

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My concern with what you've done, polystyrene is not vapour tight, so whilst it may have slowed vapour transfer down into garage it won't have stopped it, this is why if speccing a van again I'd bit the bullet and have the electric element combi.
When we use electric heater in van we put it in the cab area, my hope being it keeps that area warm and stops condensation.
For the doors, you need to stick on closed cell insulation, if you google it you should get results
Foil backed insulation board was my preference but it was out of stock so I used polystyrene.
Maybe the wamer inside, greater temp difference so worse condensation?
I guess that 10mm closed cell foam would maybe resolve the footwell and door issue in either self adhesive or foil backed?
 

Tookey

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My new works van has horrible condensation in the back, previous had no problem and as far as I can tell the only difference between new and old is that this bulk head is not vented so minimal air exchange in the back
 

Nesting Zombie

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I know it’s not a great picture but I’ve tried to do something to demonstrate my point.
I put the Gas hob on & Boiled the Kettle with ALL Doors, Windows & Vents SHUT, I Then put the Kettle steam on the window that of course results in Condensation, Now I’ve JUST opened the Dash Vents with No Engine Running, No Heater on, Keys aren’t even in ignition, but by the time I’ve Packed away & had a slurp of Coffee-
35999F3B-737C-4FE8-8502-38153E917ECF.jpeg

Can you see the bottom of the window by the vents clearing already ?
image.jpg


(Yes I’ve now re opened ALL My Vents again now)
 

colinm

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I guess that 10mm closed cell foam would maybe resolve the footwell and door issue in either self adhesive or foil backed?
The problem with using that on the floor, is that it probably won't stand up to a lot of being walked on, but I guess better than nothing.
 

Nesting Zombie

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I’ve just used 12mm Interlocking Mats ABSOLUTELY EVERYWHERE on all my Vehicles & even some boats in the past.
They seem to do the job just fine for my purposes-
0EF46E0D-2356-465B-AB5E-E3761C6FA8CF.jpeg
6F2BFBC6-CFF1-4DBB-88A8-AAF203D461B8.jpeg
 

Phantom

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The problem with using that on the floor, is that it probably won't stand up to a lot of being walked on, but I guess better than nothing.
Not really any problem as it's only under the pedals and where the jack lives on the floor area, the main mat is really tough anyway.
 

Nesting Zombie

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Just as a foot note of ‘Interest’ to my example on the windshield earlier. It’s been 3hrs or so now & -
5BDF4A29-3EC8-42FB-83D9-F2C357DC9666.jpeg

You can clearly see the moment of air & the reduced condensation.

Anyway you get the idea 👍😊
 
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