Anti Condensation Screens

[Ridgewoodwoody]

I realise this might be quite a naive question but should you put this on even if, as we are, not using the MH over winter? Our new screen arrives today and would be grateful for advice.

[laimeduck]

Is it an internal or external screen?

If internal then you could, if external I'd say No - Water will get between the windscreen and screen and it would mostly go mouldy.

You really only get condensation when the van is in use, so really not worth it.

If you have cab curtains then shut them.

Jeremy

[Derek Uzzell]

Alistair

 

I notice that you began motorcaravanning in August 2020, but I don’t think you’ve provided any details of the motorhome you own.

 

If you are referring to external ‘thermal’ blinds for a motorhome’s cab windows (examples on following link) the primary value of these is when the motorhome is being used.

 

https://www.leisureshopdirect.com/caravan-accessories/caravan-blinds/motorhome-thermal-screens-motorhome-thermal-blinds

 

Such blinds significantly reduce heat-loss through the glass of the cab windows and pretty much eliminate condensation forming on the inside surface of the window-glass. However - unless you plan to heat your motorhome’s interior when it is not being used - I’m not sure what anti-condensation benefits fitting external thermal blinds would otherwise have, though they might help to reduce fading of upholstery in the cab area. Also, if your motorhome will be parked outside during the winter, external blinds will inevitably get grubby.

 

Cab internal thermal blinds are much less effective at limiting heat-loss or preventing condensation, but at least they will be protected from the weather and won’t get grubby.

 

I’ve had both types of thermal blind, but I’ve never fitted either type while my motorhome was out of use. (My motorhomes have all been kept outside.)

[Ridgewoodwoody]

Thank you - most helpful.

[Brian Kirby]

Alistair, condensation forms when warm, relatively moist (humid), air meets a cold surface. So, to prevent condensation one needs either to dry the air, or to eliminate, as far as possible, the cold surfaces.

 

In an unused van in winter most surfaces will be cold unless some form of heating is introduced. The only source of humid air will then be from the general changes in air humidity outside, some of which will permeate the van via its inbuilt (accidental and deliberate! :-)) permanent ventilation provision.

 

This may be added to on sunny days when (assuming the van is exposed to the sun) the temperature in the van will rise, also raising its internal air temperature. When this happens the warmer air in the van will tend to draw out any moisture trapped in its soft furnishings (curtains, seat cushions and backrests, mattresses etc) so adding to the humidity of the air.

 

Then, when the sun disappears and temperatures fall, there will be a bubble of warm, relatively humid, air in the van that will, as the van fabric cools, tend to condense out its surplus moisture onto these now cool surfaces. The less absorbent the cool surface, the higher the likelihood that the condensation will be noticeable as "misting", usually towards the bottom edges of items such as windscreens and cab windows.

 

This cycle will continue day and night, from sunny days to cool days, and as atmospheric humidity levels vary.

 

So, the remedy for condensation, and the risks of mould that it brings, is, as above, to maintain a source of heat in the van, or to introduce a means of dehumidifying air in the van.

 

Probably the simplest method of drying the air is to place silica gel packets (preferably on saucers or similar) around the van. These will absorb atmospheric moisture, so that the gel becomes damp, but can be recycled by placing in a dry over at about 120C for an hour or so. The more expensive alternative is to place a small dehumidifier in the van - but this requires maintenance of an electricity supply to the van.

 

If using a heater, this must produce dry heat, so anything like a portable oil, or gas, fuelled heater is out, because water forms a large part of their combustion by-products. A low wattage electric oil filled radiator or, as I use, a low wattage electric greenhouse frost protection heater (if still available!) would be the obvious choices. But, as with the dehumidifier, either needs the maintenance of an electricity supply to the van. Only in this case, IMO, would it be worth using an insulated cab blind (preferably external, to keep the windscreen and cab windows warm so minimising their condensation risk) to minimise heat losses and so reduce the running time, and so cost, of the heater.

 

Which will best suit you will depend on whether or not you are able to maintain an electricity supply to your van and on the extent to which your van may be prone to solar heating/cooling cycles while parked up, and to the part of the country in which you live, which largely dictates the daily, and seasonal, temperature and atmospheric humidity ranges to which you are exposed.

 

One further measure that would help considerably, but requires storage space in your home, is to remove all carpet, mattresses, seat cushions and seat backs into your house, as these are the main sources of stored moisture in the van. If you can do that, unless you live in a area that is subject to extreme temperature and atmospheric humidity fluctuations, you should be able to more or less forget condensation risk, and just occasionally open up your van to air it out on fine, dry, days.

[Ridgewoodwoody]

Brian,

Many thanks for your very comprehensive reply. Most useful.

[witzend]

Ridgewoodwoody - 2021-11-27 12:05 PM

 

Brian,

Many thanks for your very comprehensive reply. Most useful.

Well are you using them or saving them ?

[witzend]

witzend - 2021-11-30 7:15 PM

 

Well are you using them or saving them ?

 

Thought He might have let us know which way he decided to use them

[Derek Uzzell]

Alistair's most recent forum logon was on 27 November 2021.

 

Alistair thanked forum members who responded on this thread and also thanked forum members who replied to the enquiry he made in September 2020.

 

https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/European-guides/56106/

 

That's a lot more than many people who seek advice on this forum do and I'm sure the forum members who took part on those two threads appreciate Alistair's thanks.

 

Even when it's plain that a final follow-up to an enquiry would be genuinely valuable (which is not the case here), there could be many good reasons (particularly nowadays) why that doesn't happen. As far as I'm concerned, this thread concluded satisfactorily with Alistair's posting of 7 November 2021 12:05 PM and I'm grateful for his thanks.

 

If you really want him to satisfy your curiosity and answer your 30 November question, you could try PMing him or enquire via the email address on Alistair's Profile.