Preventing condensation

Jul 18, 2017
1,944
378
5,935
Wheel arches in caravans tend to suffer from a lot of condensation due to their location. As we have a twin axle the area is a lot larger for even more condensation. To get around the issue we bought some 10mm self adhesive closed cell foam deadening van insulation of eBay. A bit of a hassle getting it onto the wheel arches as it sticks to everything, but it seems to work. Now considering placing some in the front gas locker under the windows to prevent condensation on the top of the shelf by the front windows. We have not had an issue there, but prevention is better than cure! See HERE.
 
  • Like
Reactions: Jcloughie
Nov 11, 2009
9,419
1,302
30,935
Seems good idea. My daughter has lined her rabbit shed with the stuff to deaden the noise they make when thumping with their back feet. Seems to annoy one of her neighbours. Cannot think why.
 
Jun 16, 2020
710
224
635
Very very sensible. I did mine a couple of years ago in a similar way. But in my van most was not fully accessible. But your material seems a great way of doing it.


John
 
Jul 18, 2017
1,944
378
5,935
Very very sensible. I did mine a couple of years ago in a similar way. But in my van most was not fully accessible. But your material seems a great way of doing it.
John
Unfortunately it was Margaret that had to wriggle into the areas to fit most of them like under the oven and back of cupboard and supervised very carefully from a distance. LOL! :D
Next is try out my idea regarding placing them in the gas locker under the shelf and above the gas bottle for warmth and prevent condensation.
 
  • Like
Reactions: Jcloughie
Jan 3, 2012
3,126
474
20,935
I have a breathable cover on and so far i have had no condensation on the wheelarches even the front box has got my thumbs up .
But if starts then i consider buying some .
 
Jun 16, 2020
710
224
635
I have a breathable cover on and so far i have had no condensation on the wheelarches even the front box has got my thumbs up .
But if starts then i consider buying some .
Condensation will only occur when it is cold outside and the caravan interior is warm and has a higher humidity that outside. ie. Occupied.

John
 
Jan 3, 2012
3,126
474
20,935
Looks like i don"t need them because i don"t use my caravan in the cold only in the warmer climate . (Thanks John for explaining about it)
 
  • Like
Reactions: Jcloughie
Jul 18, 2017
1,944
378
5,935
Condensation will only occur when it is cold outside and the caravan interior is warm and has a higher humidity that outside. ie. Occupied.

John
Perhaps if the caravan is in storage during the day it may heat up and keep that bit of warmth after the outside temperature has dropped. Maybe this could also result in condensation?
 
Jun 16, 2020
710
224
635
Perhaps if the caravan is in storage during the day it may heat up and keep that bit of warmth after the outside temperature has dropped. Maybe this could also result in condensation?
Possible but unlikely as the humidity would be equalised.

John
 
Jan 3, 2012
3,126
474
20,935
Sometimes i wish it was indoor storage but no it in outdoors caravan storage and putting the breathable cover on is beginning to be a nightmare .
 
Mar 14, 2005
13,556
674
40,935
Possible but unlikely as the humidity would be equalised.

John
Not quite,

Humidity is the concentration of water vapor present in the air. but how much water is dependant on the temperature of the air and water and its water vapour.

As you say the creation of condensation is the result of warm humid air coming into contact with a cooler surface. But the reason it happens is because warm air has a greater moisture carrying capacity than cooler air. and as humid cools it will drop any excess moisture it has.

Wood and other absorbent materials will also demonstrate similar characteristics.

In a stored caravan if sun shines through a window in the morning and its light falls on an internal non absorbent surface, the surface will warm a little. The air against it will also warm and thus it humidity will reduce. As warmer air rises it will begin to convect around the inside of the caravan. As it passes any absorbent surface, it will pick up some additional moisture and dry the surface a little.

As the warmed air losses its temperature it will descend, and as its now cooler it will start to get rid of the moisture it picked up a few moments ago. The excess moisture forms condensation, which will show on non absorbent surfaces, or be absorbed by the absorbent surfaces.

As the sun moves around different surfaces will sequentially warm up and then cool down as the direction of the sun changes. Just the sun on different external surfaces can cause this effect inside the caravan.

Now the changes are small, but if you have any condensation then it does mean the air humidity is just in that critical range of temperatures.

This is bigger problem when a caravan has just been put into storage after its been used, becasue during use, the caravan is usually kept warmer, thus both the air and the absorbent materials will be warmer and consequently have a greater moisture holding capacity. When the caravan is put into storage the temperatures drop, and all the moisture laden materials find they have to get rid of the excess moisture which appears as condensation.

Provided the caravan is set up to air and its fixed ventilation is not obstructed, the excess moisture will be carried away by the exchange of air with the outside.

Provided there are no water leaks that will soak parts of the caravan, after just a two or three days the average humidity of the caravan will normalise with the outside level of humidity. This is why a dehumidifier may have a benefit for a few days in a stored caravan, but longterm that benefit disappears, and it's a waste of money keeping a dehumidifier running long term.

But as described at the top there may well be some local internal transfers of humidity as the sun or other sources of heat affect parts of the caravan.
 
Jun 16, 2020
710
224
635
Not quite,

Humidity is the concentration of water vapor present in the air. but how much water is dependant on the temperature of the air and water and its water vapour.

As you say the creation of condensation is the result of warm humid air coming into contact with a cooler surface. But the reason it happens is because warm air has a greater moisture carrying capacity than cooler air. and as humid cools it will drop any excess moisture it has.

Wood and other absorbent materials will also demonstrate similar characteristics.

In a stored caravan if sun shines through a window in the morning and its light falls on an internal non absorbent surface, the surface will warm a little. The air against it will also warm and thus it humidity will reduce. As warmer air rises it will begin to convect around the inside of the caravan. As it passes any absorbent surface, it will pick up some additional moisture and dry the surface a little.

As the warmed air losses its temperature it will descend, and as its now cooler it will start to get rid of the moisture it picked up a few moments ago. The excess moisture forms condensation, which will show on non absorbent surfaces, or be absorbed by the absorbent surfaces.

As the sun moves around different surfaces will sequentially warm up and then cool down as the direction of the sun changes. Just the sun on different external surfaces can cause this effect inside the caravan.

Now the changes are small, but if you have any condensation then it does mean the air humidity is just in that critical range of temperatures.

This is bigger problem when a caravan has just been put into storage after its been used, becasue during use, the caravan is usually kept warmer, thus both the air and the absorbent materials will be warmer and consequently have a greater moisture holding capacity. When the caravan is put into storage the temperatures drop, and all the moisture laden materials find they have to get rid of the excess moisture which appears as condensation.

Provided the caravan is set up to air and its fixed ventilation is not obstructed, the excess moisture will be carried away by the exchange of air with the outside.

Provided there are no water leaks that will soak parts of the caravan, after just a two or three days the average humidity of the caravan will normalise with the outside level of humidity. This is why a dehumidifier may have a benefit for a few days in a stored caravan, but longterm that benefit disappears, and it's a waste of money keeping a dehumidifier running long term.

But as described at the top there may well be some local internal transfers of humidity as the sun or other sources of heat affect parts of the caravan.
Fully agree, (but you missed out interstitial condensation)! 😁. But I think my summary covered that with ‘possible’.

During storage I leave the roof blinds closed, just have the fly screen pulled across. This has the effect of raising the internal temperature during nice days. This theoretically could cause a little condensation for the reasons you mention. However, I feel the increased air movement bringing in air through the fixed ventilation, more the compensates.

As an added benefit, when using the van after storage, it does not feel like the cold has penetrated the structure to the same extent.


John
 
Last edited:
  • Like
Reactions: ProfJohnL
Aug 17, 2019
36
5
535
I have my van on the drive at home its always conected to the main electric and throughout the winter months when not in use as we uselly caravan all year around i have a electric heater pluged in always keeping everything warm inside the van so what folk are saying i should not be doing this in fear of condansation in the van wr also use deuminfiers to catch any moisuture in the air inside the van
 
Jun 16, 2020
710
224
635
I have my van on the drive at home its always conected to the main electric and throughout the winter months when not in use as we uselly caravan all year around i have a electric heater pluged in always keeping everything warm inside the van so what folk are saying i should not be doing this in fear of condansation in the van wr also use deuminfiers to catch any moisuture in the air inside the van
As I said, some thermal rise will encourage airflow through the fixed ventilation which, in my opinion, (not scientific). Should counteract any build up of condensation. But that also means that, to an extent, you will be heating the outside air which is rather wasteful. But no doubt it feels nice. Also, if you do have reasonable fixed ventilation, the dehumidifiers will be pulling moisture out of the atmosphere!

John
 
  • Like
Reactions: ProfJohnL
Mar 14, 2005
13,556
674
40,935
I have my van on the drive at home its always conected to the main electric and throughout the winter months when not in use as we uselly caravan all year around i have a electric heater pluged in always keeping everything warm inside the van so what folk are saying i should not be doing this in fear of condansation in the van wr also use deuminfiers to catch any moisuture in the air inside the van
Basically all you need is good ventilation and make sure you open doors and lockers to give the air a chance to circulate everywhere. Its even advisable to remove soft furnishings.

Adding heat during storage will not reduce the quantity of water vapour in the air or fittings below the ambient density.

Using dehumidifiers can be an advantage for a few days but long term all it does is to extract humidity from the air which passes through the caravan, which is of course replaced as fresh moist air enters as the dried air escapes.
 
  • Like
Reactions: Jcloughie
Nov 11, 2009
9,419
1,302
30,935
I’ve never used heat in a stored caravan and never had mould. As Prif John advises I open every cupboard, locker, draw and wardrobe. All seat and bed furnishings are lifted to allow free air circulation. The net effect resembles an explosion in a furniture factory. But there’s never any mould. But do remove the aerosol of Pledge from anyone who plans to use it as the waxes will encourage surface mildew.
 
Mar 27, 2011
808
224
19,135
I’ve got another use for the insulation panels if I can get hold of some, I’ve got a toilet cistern that is inside a vanity unit, at home not in a caravan lol, and I get condensation on the outside of the cistern, not to a massive amount as I had some fairly thin polystyrene that i used to cover the tank, didn’t stop it totally but it was less, those panels would be better though so I’ll look for them online.

BP
 
Jun 16, 2020
710
224
635
I’ve got another use for the insulation panels if I can get hold of some, I’ve got a toilet cistern that is inside a vanity unit, at home not in a caravan lol, and I get condensation on the outside of the cistern, not to a massive amount as I had some fairly thin polystyrene that i used to cover the tank, didn’t stop it totally but it was less, those panels would be better though so I’ll look for them online.

BP
You may also want to introduce some of these into the unit. If it can be done discreetly.

1606502082949.png

Lots of colours and sizes available. The free air movement may keep the condensation down a bit.

John
 
Jan 3, 2012
3,126
474
20,935
We never used heat in a stored van and never had mould we open every cupboard ,locker draw, fridge door & wardrobe door we even take the cushions out empty the van . to allow the air circulation .
 
Nov 16, 2015
6,046
419
17,935
I’ve never used heat in a stored caravan and never had mould. As Prif John advises I open every cupboard, locker, draw and wardrobe. All seat and bed furnishings are lifted to allow free air circulation. The net effect resembles an explosion in a furniture factory. But there’s never any mould. But do remove the aerosol of Pledge from anyone who plans to use it as the waxes will encourage surface mildew.
I must admit since I managed to stop, Mrs H, using the "Pledge" stuff prior to going back to storage site, we have had no problems with mildew type stuff.
 
  • Like
Reactions: otherclive
Mar 27, 2011
808
224
19,135
Good idea John, I could easily cut a couple of holes in the unit to let air circulate, I’m expert but I’ve got the cistern in the vanity unit, the tank is full of cold water so warm air getting into the vanity unit surely will condense on the cold tank, if I were to put air holes in the vanity unit I would have thought more warm air would enter and condense, if there was enough warmth to raise the cistern water temp then that would work but that’s not going to happen, there’s not lots of condensation currently but more than I’d like.

BP
 
Mar 27, 2011
808
224
19,135
Re the caravan I’ve never heated it in winter and I’ve never had mildew either I just do the soft furnishing explosion method and touch would it’s worked so far..

BP
 
Jun 16, 2020
710
224
635
Good idea John, I could easily cut a couple of holes in the unit to let air circulate, I’m expert but I’ve got the cistern in the vanity unit, the tank is full of cold water so warm air getting into the vanity unit surely will condense on the cold tank, if I were to put air holes in the vanity unit I would have thought more warm air would enter and condense, if there was enough warmth to raise the cistern water temp then that would work but that’s not going to happen, there’s not lots of condensation currently but more than I’d like.

BP
If your cistern was exposed to the room, as most are, then, although they get some condensation on them, it is not usually a major problem.

But yours is enclosed!!!,

Easy way to test, if you leave the enclosure open for some hours, does the problem get worse or better?

John
 
Mar 27, 2011
808
224
19,135
I worked on some vans for a big mobile plumbing company and had a natter with several of the plumbers and they said it’s quite common, apparently one solution is a double skinned cistern so the outer skin is not in contact with the water due to a gap between the two skins, not easy to get one and they reckoned they are an expensive item, I’m currently revamping the bathroom and intend to fit a new vanity unit so I’ll try and get some of the insulation panels that started this thread.

BP
 
Nov 11, 2009
9,419
1,302
30,935
Good idea John, I could easily cut a couple of holes in the unit to let air circulate, I’m expert but I’ve got the cistern in the vanity unit, the tank is full of cold water so warm air getting into the vanity unit surely will condense on the cold tank, if I were to put air holes in the vanity unit I would have thought more warm air would enter and condense, if there was enough warmth to raise the cistern water temp then that would work but that’s not going to happen, there’s not lots of condensation currently but more than I’d like.

BP
We had an open cistern in a downstairs cloakroom and it would get condensation even when heating was on. It would drop onto the floor and leave small puddles. Very much dependent on atmospheric conditions or if cooking where the kitchen wasn’t far from the cloakroom.
 

ASK THE COMMUNITY

TRENDING THREADS

Latest posts