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Steamy Windows


dtg

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Hi all

 

Just noticed on the van (3 year old Bailey Bordeaux) that one of the windows has a small patch of misting in between the double glazing at the front, any ideas or will it evaporate as soon as we get some warmer weather?

 

Dave

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Remove the little plastic plugs on a dry sunny day and wait for the internal misting to clear. Then replace plugs.

 

Brian

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Thanks Brian, sounds so simple, i'll try it out when the weather is warmer.

 

dave

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Guest mr_sheens

NEVER EVER remove the bungs in windows, this makes the problem worse. windows do sometimes have condensation in them, but as long as they clear, its not a problem. if they dont clear, new windows are required.

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NEVER EVER remove the bungs in windows, this makes the problem worse. windows do sometimes have condensation in them, but as long as they clear, its not a problem. if they dont clear, new windows are required.

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If the bungs aint meant to be removed. ..why are they there ????

 

I was always given to understand that if you get condesation, then remove the bungs until cleared ??

 

Can you please explain why you should never ever remove them ???

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Guest mr_sheens

the bungs are there to regulate the amount of air circulating in the window. on warm days the windows expand slightly and this expells some of the air inside. again on cold days the windows will contract. that is what the bungs are there for, but the holes in them are very minor.

 

its an old wives tail about taking the bungs out.

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Removing the bungs has worked for me in the past. Internal condensation is caused by too much humidity inside. Removing the bungs is the only way to release this. As I said previously, choose a dry sunny day, preferably with the sun shining on the affected window.

 

Alternatively you can buy a new window at Mr_Sheens dealership, but its lots cheaper to remove the bungs. Don't forget to replace them later, otherwise it would allow moisture back in.

 

Brian

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The Owners Handbook for my Sterling Eccles Topaz quotes the following.

 

"As your caravan is double glazed you may occasionally get condensation inside the double glazing. This is particularly so in severe weather change (usually spring and autumn) and is easily cured in dry weather.

 

1) Remove the plastic plugs from the interior top of each window.

 

2) Leave unplugged for approx 1-4 hours until condensation has cleared."

 

Hope this is of some help. ...Paul

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What are the bungs for?

 

When the windows are made the inner pane is cemented to the outer pane using a solvent adhesive. An air pipe is fed into one bung hole and an exit pipe is fed into the other and air is blown through in order to remove the solvent fumes produced during assembly. The fumes are collected centrally. If the fumes from the solvent are not removed the acrylic panes will crack all over.

 

I used to run a caravan window factory and this is how we used to make them.

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Guest mr_sheens

polyplastic who make the windows, advise not to remove the bungs. this is especially important if a window is still under the manufacturers warranty. if the bungs have been removed or damaged in any way, they may not honour the warranty on the window.

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I have an Abbey Vogue and the recommendations from them is that if there is condensation between the window panels, REMOVE the bungs for 4 hours (in dry weather, obviously) to allow the water vapour to disperse, then refit the bungs.

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Remove the little plastic plugs on a dry sunny day and wait for the internal misting to clear. Then replace plugs.

 

Brian

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Hi Brian,

 

This is the recommended method across the Swift Group,at least Swift,Abbey and Sterling. I wonder what other manufacturers advocate. :)

 

It also states this in the Caravan Manual by John Wickersham. Common sense really.

 

Frank

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Frank,

 

I looked in my Bailey handbook and there is nothing mentioned about windows. I doubt if they would change them under warranty if they steamed up.

 

Brian

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Guest john1215
the bungs are there to regulate the amount of air circulating in the window. on warm days the windows expand slightly and this expells some of the air inside. again on cold days the windows will contract. that is what the bungs are there for, but the holes in them are very minor.

 

its an old wives tail about taking the bungs out.

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Surely, if you don't remove the bungs then on a warm day the air can't be expelled with the bung in, the bung will stop the air being expelled?

If the bungs allow the expanded air to escape then they themselves can't be airtight so in that case. removing them can't be detrimental, can it???

 

john1215

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The Owners Handbook for my Sterling Eccles Topaz quotes the following.

 

"As your caravan is double glazed you may occasionally get condensation inside the double glazing. This is particularly so in severe weather change (usually spring and autumn) and is easily cured in dry weather.

 

1) Remove the plastic plugs from the interior top of each window.

 

2) Leave unplugged for approx 1-4 hours until condensation has cleared."

 

Hope this is of some help. ...Paul

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My book say's this as well

Pete.

Volvo
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polyplastic who make the windows, advise not to remove the bungs. this is especially important if a window is still under the manufacturers warranty. if the bungs have been removed or damaged in any way, they may not honour the warranty on the window.

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They would do, so that people have to go to the considerable expence of replacing windows.

 

How could the manufacturer say it invalidates the warrantee, if it says to do it in thier manual?

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I'm not a technical expert - and I'm not in the trade - but my understanding of the double-glazed windows fitted on moderm caravans was, that after the two halves of the window had been bonded together, and all noxious fumes expelled, then the air was withdrwn in a sealed vacuum chamber - thus creating a vacuum within the sealed unit. The bungs are then fitted to prevent the ingress of moist, or any other kind of, air. The presence of condensation within the unit is an indication that one of the bungs sealing the unit has failed. Thus the vacuum has gone. Yes - to remove the condensation, you can remove the bungs on a warm day. But to effect a permanent solution the window has to go back to the factory, or a replacement purchased.

 

No doubt I'm barking up the wrong tree. But that was told to me by a caravan dealer. "Yes, mate, just like the double glazed windows at home."

 

Won't take long for some body to tell me.

 

The other "cure" for windows with condensation between the two surfaces is "silica gel", which isn't a gel, but crystals that absorbe moisture.

 

ATB

You can not reason with an unreasonable person.

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Phil,

 

Don't see how there can be a vacuum in the windows. The plastic is very flexible and if you did pull a vacuum I am sure the two panes would pull together. Ever seen what happens to a coke can when you pull a vacuum on it? However I am not an expert. .......

 

 

Brian

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Hi Phil and Brian,

 

I don't claim to be an expert but have certainly had a fair amount of experience with differential pressures. You would never achieve a full vacuum in practice anyway and if you did you would have 14. 7psi acting on the surface of each side of the window. If the window was 20"x30" that is 600sq" x 14. 7 x 2. Even with a pressure diferential of 1psi that would be a loading of 1 x 600 x 2 = 1200lbf. I don't think caravan windows are that strong. :)

 

The pressure inside must equal the pressure outside.

 

Frank

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So, basically, the notion of "double glazed" caravan windows is a gimmick - not a practicality.

 

The whole purpose of "doulble glazing" in a house is that the 'vacuum' inhibits the transfer of both sound and heat/cold. As in "vacuum flask". Now they're pretty thin, aren't they?

 

Well, there you are then, never too old to learn something.

 

Not really worth getting excited about whether it's OK to remove the bungs then.

 

ATB

You can not reason with an unreasonable person.

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Double glazing is just that,two layers of glazing,sealed at the edges,there is no vacuum. The air or inert gas between the two layers has a lower emissivity than the material used to form the outer layers. Specially coated outer layers can reduce heat transfer even more. Here's one of many links:-

 

http://www. greenhouse. gov. au/yourhome/technical/fs18a_2. htm

 

The 'vacuun' flask is extremely strong because of its shape,similar in fact to a gas cylinder. The strongest shape is a sphere,the weakest is a flat sheet. You won't see any pressure vessels with flat sides.

 

Frank

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