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I'm sure this has been covered many times but here we go again!

 

The front roof window on our Commodore had developed a very slight mist in a lower corner.  I had this on our last van - Swift Challenger but the problem remains the same as all the windows only come from a couple of manufacturers. Its guess its impossible to construct a completely air tight and moisture  proof unit.

Does anyone have any definitive means of removing this? There have been opinions that the plugs are actually one way valves? Is this the case?

The plugs are still intact and I assume there are two methods: remove the plugs and wait OR do nothing.

I might turn the van round to face the sun and see if it clears.

 

What do you think?

 

Cheers

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Every van we have ever had with ‘double glazed’ windows has experienced misting to differing degrees.

These windows are not sealed units like you get in a house.

Some advocate removing the bungs, but we have always just left ours and eventually they clear.

Must admit though, we never had a roof window misting.

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Is it always there, or dos it come and go? The fact that you think turning the van round to face the sun implies it's the latter.

Taking the plug out will allow ambient air (and any bugs, so beware!) to enter the gap and hopefully allow the moist air out, or not, depending on the moisture content of the ambient air.

However, replacing the plug will simply trap that ambient air inside, and if it's a warm, humid day when you put it back, the air inside will have a lot of moisture held as a gas. That moisture will then condense out again on a cold day and you'll be back to square one.

 

My advice is:-

Unless it's intolerable, I would leave it alone.

If it's intolerable, and always there, try taking the window inside the house, take the plug out and leave if for a day or so, then replace plug and window.

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Posted (edited)

Sorry - my description was a bit confusing. The Buccaneers have a high level fixed front window. No its not actually in the roof and cant be removed - apologies for that.

Van is one year old. First time its appeared - it has been very cold and wet and today has been relatively warm so it all adds up.

Edited by yorkyguy
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Its guess its impossible to construct a completely air tight and moisture  proof unit. It isn't but they are more expensive and can suffer from distortion and the joint between the inner and outer pane opening up due to excess internal air pressure on very hot days.

 

Does anyone have any definitive means of removing this?  As you mention below having them facing the sun helps on a hot day along with removing a couple of plugs, easy but awkward in that in  removing and re-fitting them they can end up inside between the panes for ever more, ( have a look at the bottom of windows on a second hand van plot. 

 

There have been opinions that the plugs are actually one way valves? Is this the case? they are not designed as such but can act as one, allowing excess pressurised air to escape when hot and allowing air inside as the internal pressure reduces when cooling.

 

The plugs are still intact and I assume there are two methods: remove the plugs and wait OR do nothing.

I might turn the van round to face the sun and see if it clears. Yes and yes, there is no detriment to leaving the plugs out other than accumulating a museum of various insects who get in but can't get back out, to prevent this a small blob of such as white BluTack can be pushed in, as long as you remember to leave a small 'head' of the tack with a larger diameter than the hole to prevent them being  pushed or sucked in.

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I've just remembered a conversation with the lads up at EECO one Saturday morning whilst I waited for a window to be made, asking the same question, one surprising fact they came up with about van windows was that in the main they are acrylic or polycarbonate and both these materials can be subject, in the right  conditions, to pass water vapour through them by permeability or diffusion, obviously at a molecular level, fascinating what you can learn when you ask questions.

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3 hours ago, Silversurf said:

I've just remembered a conversation with the lads up at EECO one Saturday morning whilst I waited for a window to be made, asking the same question, one surprising fact they came up with about van windows was that in the main they are acrylic or polycarbonate and both these materials can be subject, in the right  conditions, to pass water vapour through them by permeability or diffusion, obviously at a molecular level, fascinating what you can learn when you ask questions.

Yes, absolutely true for every plastic.

All will allow absolutely tiny amounts of water vapour to pass through, but generally it's so slow and in such tiny amounts it's not really a problem. But given time, vapour will pass through, both ways.

 

My advice  remains to do nothing, just wait and it will sort itself out, eventually.

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My last four Swift’s have had the panoramic roof window and on certain mornings they all had slight misting inside the panes. I remember others reporting the same on Swift Talk.

2018 Volvo V90 and 2018 Swift Sprite Quattro EB

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The seal on the centre window went on my van and was letting moisture in.

It was constantly misting up badly. I tried re-sealing the join, removing the plugs, applying gentle heat etc, but the problem kept coming back.

Went to the van one morning to find water about 3" deep inside the window.

I eventually drilled three holes along the bottom of the inside of the window, to drain the water.

I left these unplugged and have not had a misting problem since.

 

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My van has no bungs (or bung holes) - a bit worried about the earlier comment on distortion?

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34 minutes ago, SamD said:

My van has no bungs (or bung holes) - a bit worried about the earlier comment on distortion?

I wouldn't worry  it's extremely rare, it can, not will, happen in extreme circumstances in areas of high ambient summer heat, so not in the UK, when a window has been directly  in full sun with thermal blinds or curtains reflecting the heat back out.

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7 hours ago, DottieD said:

I eventually drilled three holes along the bottom of the inside of the window, to drain the water.

I left these unplugged and have not had a misting problem since.

:goodpost: I do like the simple solutions :)

Fourwinds Hurricane 31D Motorhome. Also MGTF135 1. 8i Roadster (fun) & Volvo V70 3.2Ltr LPG (everyday car)
Unless otherwise stated, my posts will be my personal thoughts and have the same standing as any other member of Caravan and Motorhome Talk.

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