condensation

[Mike S]

Does anyone suffer from condensation in a monocoque body motorhome? We have just returned from 2 weeks in the Lakes without any rain but very cold, down to minus 6.8deg.C some nights. Between the outer and the inner skin, the side panel behind the caravan door near the kitchen end, was wet from top to bottom. The carpet was taken out and newspaper pushed under the cupboard side wall and changed twice a day due to being wet. The roof light was checked and was dry, there are no windows in that area, water pipes were checked and also the waste. On returning home, we also found it was very wet under the off side bunk.

[Brian Kirby]

You don't mention the make or model of your van, Mike, but I'm guessing Autosleeper.  In my view (and I'll get into trouble for saying this), Autosleepers are not truly winterised.  I suppose more fairly, they are UK winterised (just), but you have been out in rather extreme conditions.

You will need to manage the condensation under such conditions.  This will mean thorough ventilation of the van every morning, and after you have done any cooking inside.  Thorough ventilation means all doors and windows, and if possible rooflights, wide open for, depending on wind, up to ten minutes. 

We all exhale moisture vapour, we perspire, and when we cook we release water vapour from the LPG as well as from the food.  That vapour will be held by the air in the van for so long as it remains warm.  However, the external surfaces are all cold (for example, I'd guess the windscreen was running with water) and the perfect vapour barrier hasn't yet been invented. 

This means the moisture in the air will quite easily penetrate the inner wall lining, and pass through the insulation, until it meets the inside of the van's outer skin.  This will be at about the same temperature as the air outside, so at or below freezing.  As the air passes through the insulation it will be cooled, and will no longer be able to carry the load of moisture it accumulated when warm.  Once it gets to the cold outer skin, it simply dumps the excess as condensation.

That is why you need to open up, and ventilate the van interior, periodically.  You need to dump out all the stale, moist air from inside and take in cold, (relatively) dry, air from outside.  This will begin absorbing moisture as soon as it arrives but, providing you keep cycling old air out and new air in, the total vapour load in the air will be kept down, and the risk of condensation much reduced.  You can't prevent it in cold weather, but you can control the extent to which it causes trouble.

[Mike S]

As we have only had your comments, Brian, we have assumed no one else suffers as we do. It isn’t only the cold weather that causes the condensation but wet weather as well. We have proved we do not have a leak anywhere – every thing that can be sealed has been resealed and a torrential downpour in the Lake District last October proved all was OK.

The back window (kitchen end) is opened as soon as we get up in the morning, albeit is only on the first catch, as are the two side windows. The back one remains open at least until the breakfast washing up has been done and the side ones until we go out – or until we can bear the cold no longer! When cooking the evening meal, the back window is open and as soon as the microwave is used, the extractor fan is put on, (we changed the existing skylight, for one with an extractor fan in it, before going away for Christmas) and all are left open or on until the washing up is completed. This can be anything up to a couple of hours! There is enough draft from the front vents to aid the extractor fan. Since fitting the fan we tend to leave the skylight open slightly most of the time.

As for the cab windows, in the winter we use outside and inside screens, as well as drawing the cab curtains at night. All screens are left in place during the day but the outside screens are folded part way down. We don’t get any condensation in this area.

The next time we go out we are going to try a de-humidifier, but to be honest we don’t think this will make any difference because the humidity in the motor home over the Christmas/New Year trip was about 40 most of the time.

We are really getting to the end of our tether and just cannot believe that we are the only ones suffering in this way. Perhaps no one else has realised they have the problem or is there something wrong with m/h?

 

[Keithl]

Mike,

 

As Brian asked previously, what Make and Model is your M/H?

If you let us know we may be able to help.

 

Keith.

[spospe]

Mike S

 

You do not mention what heating arrangements you are using, or what temperature you maintain the interior of the van at. The warmer the air, the more moisture it can support before condensation can form, so this may be something to have a look at (as well as possibly making the inside of the van more comfortable to live in).

 

From what you describe, something is wrong. I have been to the North Cape of Norway several times and had water pipes freeze under our Autosleeper Duetto, but never had condensation such as you mention in a heated van.

 

Michael

[Brian Kirby]

Mike

Two things.  First, you say the wall aft of the door is wet between the skins.  Forgive the question, but how do you know?  Between the skins is not, normally, visible!

Second, from the volume of water you are experiencing, and from your description of your use of the van, it is improbable, in my opinion, that this can be condensation.  I am convinced you have a leak.  If your van is an Autosleeper (but please clarify), have you checked around the fridge vents?  From another post on this forum it seems these can be the source of leakage, particularly on monococque Autosleepers.  Any external hatch, door, or window might be the source: this just seems to be far too much water for condensation alone.  Unless, that is, the shell of your van is completely devoid of insulation!

[Guest JudgeMental]

You need to fit the covers on both fridge vents, the vents are only to assist cooling in hot weather. Condensation to me normally means, bad design/ poor structural ventilation. Also someone else said are you heating the van sufficiently as well? It would help to know what van you have.

 

also just because the inside of a roof light/window appears dry, water ican be penetrating through a faulty exterior seal and working its way down and into the van some where else....

[Mel B]

From the descriptions, I suspect this is an Autosleeper, traditinal layout with 2 settee's up front, either side under the windows, on the offside is the wardrobe with washroom in the rear corner, and on the nearside at the rer of the sofa is a unit, then the caravan door, then the nearside/end has the kitchen until across the rear of the van. The unit you are talking about I believe is the one in the rear nearside corner? If so, then I would suspect a lead from the kitchen unit is possible - have you checked the water pipes and waste pipe for signs of a leak? If it's not that then you may have a leak of some sort in the bodywork (a crack?) which is allowing water in.

 

Another alternative is that the water is channeling into that area from somewhere else, either down the wall (possibly gaining entry from the rear window, or around the caravan door, or maybe up on the roof - have you checked this for damage/repair? ARe there any accessories fastened to the rear/side that again could be allowing water to enter - think of bike rack/ladder/roof rack/external door securing device etc, etc.

 

With the amount of water you are experiencing I find it very hard to believe that it is condensation.

[Brian Kirby]

Or, if you have an awning, the fixings for that, which usually go right through the side walls.

[Guest peter]

Get a damp tester from someone like B&Q and have a prod around to find the dampest part of the structure. But if it's very wet you need a Desiccant De-Humidifier (£99 from Maplins) to get rid of the moisture. We have ours on all night on our boat in winter and have totally clear windows in the morning. Just a couple of hours on Turbo setting will clear 2 Ltrs. They are fitted with a timer and I put it in my M/H for 4 Hrs every fortnight and always clear some water out of it.

[Derek Uzzell]

Mike

 

There is no technical reason for a motorhome with a properly insulated monocoque bodyshell to be any more prone to condensation within the living-area than a vehicle differently constructed.

 

As far as I'm aware Auto-Sleepers (assuming your motorhome was made by that company) have, from at least 1996, used Styrofoam insulation for monocoque bodies, but I don't know how this material is employed.

 

As a specific patch of interior walling seems to be involved and the wetness is from the top to the bottom of the wall, I suppose there's the possibility that the between-walls insulation has failed (or that there is no insulation behind the inner surface!) If your motorhome were quite elderly and used a non-rigid form of insulation (eg. glass-fibre wadding) between the walls, then there's a real chance this has degraded and fallen to the base of the walling, leaving a section of the wall uninsulated.

 

With no details of make, model or year of motorcaravan, it's very difficult to offer better than educated guesswork. It would also be useful to know how long you have owned the vehicle and whether or not the problem has always been evident.

 

(Sadly - and, Heaven knows I've said this enough times - there's no prompt at the forum registration stage to encourage new members to provide information about their motorhomes and, although there's a OAL Moderator thread about this ("What are the vehicle details?") towards the top of the Motorhome Matters main webpage, this is easily and regularly overlooked.)

[Mike S]

We have an Auto Sleeper Gatcombe 2002 model.

We have electric blown air heating which is on 500 watts and set at around 70 degrees. Unfortunately the wife has Raynaud’s Disease so we have to keep the m/h as warm as possible. We also have a small 700 watt oil filled radiator that we place in the cab area – this helps to keep (what we think is) the coldest part of the m/h warm. The heating is turned down at night although we do leave the radiator on.

We first realised the problem when we returned home from holiday Christmas/New Year 2007 – it as good as rained the whole three weeks we were away – so we thought we had a leak. How long it had been going on we have no idea. The m/h is coming up to 7 years old and we had it from new. There followed, over 2008, various checks and resealing.

The cupboard was dry, apart from the carpet on the floor, with no leaking pipes, no leaking sink and all was sealed OK round the worktop area. The top light clusters were resealed as were the bottom ones, the bike rack fixings were resealed, the ladder fixings were resealed and also the window, although no wet could be found actually inside at the back of the m/h. The skylight appeared to be OK but in December we changed it for an extractor fan one and that was properly sealed. The only things left were the roof bars and when we realised his we thought, great we’ve cracked it, they must be the problem. They were duly resealed and off we went on holiday. We were in the Lake District the weekend of the torrential downpour and flooding in Borrowdale that made the national news. We were so cocker hoop because we stayed dry – for about a week, then it all started again. The rain was so bad that weekend that if we had a leak it would have manifested itself within twenty-four hours. Hence the reason we are back to thinking we have a condensation problem. After all the resealing we did, we got the jet hose on it – and it withstood the blast of water, no leaking whatsoever.

To find out more about where the damp was coming from we managed to release the inside wall above the door and above the sink unit in the back corner, enough to be able to feel it was wet from the sink unit upwards. We have fibre glass wadding installed by AS which was still intact, although thin. We have since increased this upwards of the sink unit. We cannot gain access to the wall below the sink unit on that side, so do not know what or how much insulation is there. As the water is down the bottom we assume it must be wet the whole way down. As far as we know all round the fridge area is OK because it is the other side of the door. As far as I can tell, there is no Styrofoam insulation in the m/h, it is all fibre glass.

We do have a damp meter and it was well worth the expense.