# Silver Screen vs Louvred Blinds (or whatever they're called)



## MrWez (Sep 25, 2011)

Hi all,

We've just purchased a MH with those fancy-dancy louvred/concertina type blinds fitted to the cab - we didn't have this on our previous MH we used an external silver screen.

I reckon the louvred/concertina type blinds will probably stop condensation forming on the glass simply because they present an immediate barrier immediately before the glass but I'm guessing they do very little in the way of insulation.

The question is this. Does anybody have any experience of touring particularly in the winter? Do the louvred/concertina type blinds do the trick or do you need an additional external silver-screen?

Over to you good people.

Regards

Mr Wez


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## RichardnGill (Aug 31, 2006)

In a word no, 

They do not stop condensation you will need external blinds in the winter. They are ok in spring autumn though.

Richard...


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## andrewball1000 (Oct 16, 2009)

I agree that they do not stop condensation but I haven't bothered with getting external covers for the winter. The bed is at the back of the MH. I wild camp a lot and like the idea of being able to drive off if I have to. I keep a big sponge in the drivers door.


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## Zepp (May 14, 2009)

RichardnGill said:


> In a word no,
> 
> They do not stop condensation you will need external blinds in the winter. They are ok in spring autumn though.
> 
> Richard...


I agree you will need external silver screen to stop condensation in the winter


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## MrWez (Sep 25, 2011)

andrewball1000 said:


> I agree that they do not stop condensation but I haven't bothered with getting external covers for the winter. The bed is at the back of the MH. I wild camp a lot and like the idea of being able to drive off if I have to. I keep a big sponge in the drivers door.


Mmm!

My understanding is that you stand a good chance of corrosion setting in - it's easier to stop the condensation forming than it is to clear it up.

The sleeping areas in our MH are in the over-cab and around the dinette so they're superbly placed for condensation to form on the glass of the cab.

Methinks I'll be getting a silver screen for our new MH - it's on a Transit base whereas our previous MH was Fiat Ducato based so the old screen doesn't fit our new MH (we know, we had a go this weekend).

Thanks to all for the advice.

Mr Wez


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## Zebedee (Oct 3, 2007)

MrWez said:


> . . . it's easier to stop the condensation forming than it is to clear it up.


That is certainly true, and external screens will virtually eliminate it, but it's not only about condensation.

If you have swivelling front seats, the cab area can become almost a no-go zone when it's very cold. Fitting external screens makes a huge difference, and ensures that the whole of the van's interior can be comfortable - even in very cold weather.

The screens can be a bit soggy to put away if wet, but they won't rot and we just chuck them in the toilet until next use, or for drying out when we get home.

Another bonus . . . if it's frosty you will not have to scrape and clear your windscreen before you can drive away.

Dave


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## alshymer (Nov 4, 2007)

*Silver Screens vs Louvre Blinds*

Hi

I am afraid I have to disagree for once. I have the new model Hymer B694
and the internal slatted electric blind which sits some 8 inches from the windscreen is absolutely brilliant.
There are not the cold spots we had in our last Hymer B 655 and we don't get windscreen condensation.
For the side windows we have just cut some 'off the roll insulation' to shape and fit this internally.
We spent the end of November and two weeks in December in Devon last year and you would not get a more severe test than that!
I always found the Taylormade External screens such a nuisance, I am really pleased not to need them anymore.
My advice- don't waste your money until you have experience a cold spell in the van.

Kind regards
Alshymer


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## Rapide561 (Oct 1, 2005)

*Screen covers*

Hi

I agree re the condesation prevention, but, if the condensation does not settle on the cold glass, where are you forcing it?

I use my screen covers more in the hot sunny weather than the winter to prevent the front of the motorhome becoming a greenhouse. I would not rely on closing internal blonds for this as the heat builds up between the blind and the screen etc and then my blinds pop open!

In winter, I use the covers too, but as I have stated previously on here, I do not think they make that much difference to warmth etc inside but do solve the condensation issue. As said though, if the condensation is not on the cold glass that can be wiped away, where have you forced it to go?

Russell


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## Blizzard (Sep 21, 2009)

We also have the concertina type blinds fitted and agree that they do not prevent condensation building up on the front screen.

We've never considered the need to fit exterior insulation, but although we've used it in some cold conditions, we haven't used it in well below freezing temperatures yet.

I agree with Russell that I would prefer the condensation on the glass where I can see it and mop it up, rather than forcing it to the next coldest spot, which might just end up being a wall or ceiling panel !


Ken.


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## Razzo (May 1, 2005)

A long time ago I did heat load calculations for designing air conditioning systems for buildings. We always allowed for an half inch of still air insulating the fixed surfaces. This is on all surfaces although we dismissed the external one due to wind moving it. Therefore when calculating the heat transfer, there is the glass, plus half inch air and if a closed curtain, another two half inches, one on each side. With conduction a 1inch airgap is equivalent to 9 inches of concrete. (Hence why a double brick house has good properties not to mention double glazing.)

Thus a blind will help in summer.

Condensation occurs on a cold surface because the temperature of it is below the dew point of the surrounding air. The humidity in a van can be high due to cooking and boiling the kettle. This will only condense on cold surfaces. If you reduce the amount of cold surfaces then less air will condense not the same amount of water over the next coldest surface. 

Thus putting external screens on the windscreen will not drive the moisture elsewhere, it would be there anyway. (usually the metal doors and doors frames in my experience)

We have skied from our motorhomes so have had cold, with the lowest being -18. We used both internal and external screens at the same time. 

Our new purchase came with internal cab blinds, but we will still buy an external screen. 

My last Boss from a few years ago often accused me of TMI (too much information) You may now agree.

Cheers

Brian


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## Zebedee (Oct 3, 2007)

Razzo said:


> My last Boss from a few years ago often accused me of TMI (too much information) You may now agree.
> Brian


Not at all Brian. TLI is what causes confusion. :wink:

Let's have a bit more of the same, eh? :lol:

1). With any *internal *screen system there will be an air gap between the screens and the window. _(And in almost all cases this will *not *be a sealed gap.)_

2). An *internal *screen clearly cannot keep the window warm, because it's on the wrong side of it. If anything it will keep the window marginally cooler.

3). Unsurprisingly ( :roll: ) moisture laden air will circulate within that air gap, and if the surface of the window is cold enough, the moisture will condense out. That is an irrefutible fact of physical science I fear . . .

4). So, with the greatest respect to those who think *internal *screens *prevent *condensation, they are wrong. Internals may *reduce *condensation if they have a fairly well sealed air gap so the circulation of the air is greatly restricted . . . which may well be the situation with Alshymer's blinds. I don't know anything about them so cannot disagree with his experiences. :wink:

5). It remains a fact however, that if moisture laden air is able to circulate and come into contact with a cold window surface, it will condense.

6). Whether or not one is concerned about water running down into the dash is a matter choice, but I would definitely be concerned. Having several times tried to mop a heavily condensed window, I was never able to catch all the runs before they disappeared into the gap between the screen and the dash.

7). The basic function of *internal *and *external *screens if fundamentally different. *External *screens keep the window warm enough to prevent virtually all condensation. *Internal *screens can't possibly keep the window warm, so cannot prevent condensation if warm, moisture laden air comes into contact with it.

8]. I forget the figures, but simply breathing all night creates more than enough water vapour to fog up your windscreen until the water runs down in little rivers.

How about that for TMI then!! 8O 8O

Dave :lol: :lol:


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## MrWez (Sep 25, 2011)

Zebedee said:


> 3). Unsurprisingly ( :roll: ) moisture laden air will circulate within that air gap, and if the surface of the window is cold enough, the moisture will condense out. That is an irrefutible fact of physical science I fear . . .


Exactly, the latent heat within the relatively warm moist air is transferred to the cold surface, when this happens the moisture is released and condensation forms on the cold surface.



Zebedee said:


> 4). So, with the greatest respect to those who think *internal *screens *prevent *condensation, they are wrong. Internals may *reduce *condensation if they have a fairly well sealed air gap so the circulation of the air is greatly restricted . . . which may well be the situation with Alshymer's blinds. I don't know anything about them so cannot disagree with his experiences. :wink:


Could be...



Zebedee said:


> 5). It remains a fact however, that if moisture laden air is able to circulate and come into contact with a cold window surface, it will condense.


The problem is glass itself is not a good insulator whereas the GRP that most MH are made from is. Glass allows the free conduction of heat through it whereas the GRP sandwich construction contains many pockets of air which act as insulators, therefore the condensation (in theory) shouldn't form on the inside of it (e.g. the roof and wall panels). Of course if it is extremely cold outside and the inside air is particularly moisture laden then at some point physics takes over and condensation would form under these circumstances. If that was the case I'd seriously have to think twice about whether I should be camping under those circumstances - or whether I should turn the heating on! 



Zebedee said:


> 6). Whether or not one is concerned about water running down into the dash is a matter choice, but I would definitely be concerned. Having several times tried to mop a heavily condensed window, I was never able to catch all the runs before they disappeared into the gap between the screen and the dash.


I'd read that this was the cause of lots of corrosion problems along the bottom of the screen on Ducato based cabs, not to mention electrical problems under the dash - surely better to stop the water collecting there?



Zebedee said:


> 7). The basic function of *internal *and *external *screens if fundamentally different. *External *screens keep the window warm enough to prevent virtually all condensation. *Internal *screens can't possibly keep the window warm, so cannot prevent condensation if warm, moisture laden air comes into contact with it.


We're back to good old physics there then!



Zebedee said:


> 8]. I forget the figures, but simply breathing all night creates more than enough water vapour to fog up your windscreen until the water runs down in little rivers.


That's the answer then - stop breathing in your sleep?:wink:

Thanks to all for your comments, science lesson aside it is very helpful finding out the views of fellow MH owners. FWIW, I've decided to try camping in the cold before deciding which way to jump - as I get very hot in my sleep i think this might help me to get a better night's sleep - my wife might not agree though!

Regards

MrWez


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## MrWez (Sep 25, 2011)

Well this weekend was the clincher with some cooler nights out in the New Forest, I wanted to leave all the roof vents and Heki open, my wife and daughter were worried they'd be too cold so we compromised - vents half open, Heki closed and the forced air heating on low.

We got condensation, I was too hot and had trouble sleeping - the girls both had a lovely nights sleep bless them!

I'll be investing in a silver screen, it won't help us find the balance between me being too hot and them too cold but at least we won't get any condensation!

MrWez


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