AlanS Posted December 31, 2014 Share Posted December 31, 2014 I have seen a thread running on another Forum about this topic but thought I would let you know of my experience today. I went out to our motorhome today (parked up at home) to put some bits in it that I had found indoors when we cleared it out last. It is about 3 weeks since I checked it last and found that the roof and high level cupboards were quite wet to the touch - in fact at some points I found ice forming on the cupboard ledges. Our motorhome has its winter silverscreen on and the windows have cardboard sheet on the insides (rather than leaving the blinds down). The roof vents are closed and only the fly screens pulled across them - we have a long panoramic roof vent and 3 smaller Heki's. It was cold in there with the on-board gauge showing about 3 degrees with an outside temperature of about 0 degrees C. I have not had this level of condensation before in either the motorhome or a caravan, except for one year with the caravan. I dried the roof lining and doors off and put the warm air heating on for an hour. When I went back into it - it was 'toasty' compared to outside and about 12 degrees C and everything was perfectly dry, even in the cupboards and bunks. I have never put the heating on before in any unit we have owned. Ventilation is by the permanent high and low level vents but I cannot open the smaller Heki's as the lowest opening is still quite wide for winter use when unoccupied. Tonight I have left a low wattage oil filled radiator on in there on a low thermostat setting. I suppose the problem could be that the outside air moisture content during the day with the sun out is still reasonably high for the time of year and as unit warms up in the daytime via the roof lights, the moisture content of the air increases but when the air makes contact with the very cold surfaces both day and night (the surfaces temperature being below the dew point of the air) the moisture condenses out on those surfaces. Has anyone else checked their motorhomes, especially those in storage to see what is happening to theirs, and do those that keep their motorhomes at home, put some form of heating on in them at times like this ? Alan Link to comment Share on other sites More sharing options...
Guest Joe90 Posted December 31, 2014 Share Posted December 31, 2014 Can only say you are mirroring the experience by one of my pals in mentioning he was experiencing the same sort of problems and was using exterior silver screens when his van was parked up and not in use, he was the only one of five of us using external screens. None of us where we park has access to a mains hookup, and using external silver screens is something I've never done, nor are any windows left with blinds shut, my logic being that some winter sun warms the interior,and with the the three permanent ventilation roof vents and I seem to remember from school that warm air rises seems to keep everything bone dry, and five vans later that still holds true, He subsequently took my advice and his condensation problem ( pardon the pun ) evaporated as well. Link to comment Share on other sites More sharing options...
Muswell Posted January 1, 2015 Share Posted January 1, 2015 I get no condensation and have no heating. If you have enough ventilation the relative humidity inside the van will be the same as outside and so there should be no condensation as long as the internal temperature is slightly above external, which you seem to have. Maybe you need more ventilation. The exception to the above is that some of the external vehicle panels can be at a lower temperature than the air temperaure because of radiation to a clear night sky ( which is why you can get frost on only some windows of a car) and so you could get internal condensation....like on the underside of old aluminium bus shelter roofs. Maybe that is the problem because of the recent clear skies and low temperatures. Link to comment Share on other sites More sharing options...
AlanS Posted January 1, 2015 Author Share Posted January 1, 2015 Muswell - 2015-01-01 9:17 AM I get no condensation and have no heating. If you have enough ventilation the relative humidity inside the van will be the same as outside and so there should be no condensation as long as the internal temperature is slightly above external, which you seem to have. Maybe you need more ventilation. The exception to the above is that some of the external vehicle panels can be at a lower temperature than the air temperaure because of radiation to a clear night sky ( which is why you can get frost on only some windows of a car) and so you could get internal condensation....like on the underside of old aluminium bus shelter roofs. Maybe that is the problem because of the recent clear skies and low temperatures. We have had the external air temperature down to at least -3 degrees C and the heavy frost on the roof of the motorhome hasn't cleared all day - usually we get a bit of sun in the morning on it but at this time of the year the sun is quite low and at a slightly different angle in the morning to have any effect. Checked our motorhome just now and everything is dry and not a sign of condensation. The heater that I put in had been on at some time as it had a warmer 'touch' about it. Must admit though that the external temperatures have certainly risen overnight. Certainly the surface temperature of the roof is somewhat reflecting the external ambient temperature with no addition of heat inside the motorhome so the air inside the Motorhome would tend to condense out on those surfaces if there is any moisture content in the air. As for ventilation there is definitely air passing through the MH as you can feel the cold draught around the base of the driver and passenger seats (typical of Fiat cabs if you haven't blanked the vents off) and of course all the roof Heki's have a permanent feature even when they are closed. Alan Link to comment Share on other sites More sharing options...
Budgie823 Posted January 1, 2015 Share Posted January 1, 2015 Hi Alan, I'm still very much a novice so this is my first winter with my first Motorhome. Since the end of November it has been parked on the driveway with a silver external screen cover fitted and all internal blinds closed. During the recent cold spell which resulted in a layer of snow and ice on the roof I decided to put a fan heater on for about one hour a day even though I had experienced no signs of condensation. Perhaps more interestingly, a few weeks ago I placed a Unibond Aero 360 dehumidifier inside. It cost around £11 online and works on the principle of a large salt tablet drawing moisture from the air. I emptied it this morning and it had collected 100 ml of water so it might be with considering for such little cost. Anyway, the bottom line is everything is bone dry so I'll continue as I have up to now. Best of luck. Link to comment Share on other sites More sharing options...
AlanS Posted January 1, 2015 Author Share Posted January 1, 2015 Budgie823 - 2015-01-01 11:25 AM Hi Alan, I'm still very much a novice so this is my first winter with my first Motorhome. Since the end of November it has been parked on the driveway with a silver external screen cover fitted and all internal blinds closed. During the recent cold spell which resulted in a layer of snow and ice on the roof I decided to put a fan heater on for about one hour a day even though I had experienced no signs of condensation. Perhaps more interestingly, a few weeks ago I placed a Unibond Aero 360 dehumidifier inside. It cost around £11 online and works on the principle of a large salt tablet drawing moisture from the air. I emptied it this morning and it had collected 100 ml of water so it might be with considering for such little cost. Anyway, the bottom line is everything is bone dry so I'll continue as I have up to now. Best of luck. Hi Budgie Good to hear that your MH is keeping condensation at bay and thanks for letting us know how yours is getting on. I would think that putting the fan heart on once a day may have helped. As for dehumidifiers I am a sceptic as they work for anything that is a sealed 'box' i.e. where no air can enter or escape. Where air can enter through vents, etc. the moisture content in the external air will not be too dissimilar to the air within the motorhome and what happens is that a dehumidifier will continue to remove moisture until that device becomes saturated (as in the case of an absorption dehumidifier) or will continue operate as in refrigeration type dehumidifiers, thereby trying to dehumidify the whole of the environment where you have parked said MH. I have checked everywhere today in our MH and that too is bone dry as you say - I won't leave it so long before checking again ! Alan Link to comment Share on other sites More sharing options...
tugga Posted January 1, 2015 Share Posted January 1, 2015 Hi Alan We have not had any problem with condensation in our motorhome this winter or any of them since we have had it. We never put our silver screens on. OH does draw the internal blinds on the road side of her as she is currently parked across the front of the house. We have a convector heater that is set to the frost temperature and I keep all my locker doors open. Never pull the heki covers over. Hope you get it sorted out soon. Link to comment Share on other sites More sharing options...
Colin Leake Posted January 1, 2015 Share Posted January 1, 2015 We run a mains powered dehumidifier four hours a day from 11am to 3pm when the temperatures should be at their highest enabling it to work best. All I can say is it does remove a lot of water and does seem to keep the van dry which I have confirmed with a proper moisture meter. We remove a lot of the cushions etc into the house. If we don't run the dehumidifier the remaining none removable fabric items always feel damp. If we do run it they don't. Link to comment Share on other sites More sharing options...
chello Posted January 1, 2015 Share Posted January 1, 2015 I tend to agree with joe90, I think silver screens stop winter sun,i leave small oil filled rad on when cold,never had ant damp or condensation problems Link to comment Share on other sites More sharing options...
Brian Kirby Posted January 1, 2015 Share Posted January 1, 2015 Go back to basics. Condensation can only happen when moisture laden air meets surfaces that are below its dew point. So, for condensation to take place in your van there has to be moisture in the air, and cold surfaces. You have described where the cold surfaces were, and have said that there was condensation, so the only unanswered question is the source of the moisture in the air. It may have entered via the ventilation you describe, or it may have been released as the van warmed during the day to condense during the night. Is it possible thare are slightly damp furnishings (seat cushions, mattresses, carpets etc in the van that could be releasing moisture in this way? If so, I'd suggest removing them to your house to dry thoroughly. Otherwise, it seems you may be the victim of the fluctuating temperature and humidities we have been having as the weather goes from cold and relatively dry, to mild and relatively moist. If the latter, you may need to increase the ventilation rate somewhat to allow the moisture to escape before it can condense. Maybe open the van up for a while during the day? Otherwise, a low temperature heater with its thermostat set to about 5C should help by keeping the night-time temperatures just high enough to eliminate the condensation. No point trying to keep the van warm, just to avoid letting it get that cold, so a bit of experimentation would be required. It is what I do, and I do not have the problem. But then, nor do others who neither heat nor dehumidify their vans - so no firm conclusions can be drawn about that! :-) Link to comment Share on other sites More sharing options...
AlanS Posted January 1, 2015 Author Share Posted January 1, 2015 Brian Kirby - 2015-01-01 1:16 PM Go back to basics. Condensation can only happen when moisture laden air meets surfaces that are below its dew point. So, for condensation to take place in your van there has to be moisture in the air, and cold surfaces. You have described where the cold surfaces were, and have said that there was condensation, so the only unanswered question is the source of the moisture in the air. It may have entered via the ventilation you describe, or it may have been released as the van warmed during the day to condense during the night. Is it possible thare are slightly damp furnishings (seat cushions, mattresses, carpets etc in the van that could be releasing moisture in this way? If so, I'd suggest removing them to your house to dry thoroughly. Otherwise, it seems you may be the victim of the fluctuating temperature and humidities we have been having as the weather goes from cold and relatively dry, to mild and relatively moist. If the latter, you may need to increase the ventilation rate somewhat to allow the moisture to escape before it can condense. Maybe open the van up for a while during the day? Otherwise, a low temperature heater with its thermostat set to about 5C should help by keeping the night-time temperatures just high enough to eliminate the condensation. No point trying to keep the van warm, just to avoid letting it get that cold, so a bit of experimentation would be required. It is what I do, and I do not have the problem. But then, nor do others who neither heat nor dehumidify their vans - so no firm conclusions can be drawn about that! :-) Hi Brian Our motorhome had its habitation checks carried out by our dealer at the end of October and all readings were very low and indicated no damp whatsoever. The interior furnishings, curtains, seats and carpets are all dry to the touch and certainly not damp in any way. In the 40+ years of 'camping' we have never kept a heater operating in either a caravan or motorhome whilst it was parked up at home (unless we were using it), As I said today everything is normal but the weather has changed and I did leave a low wattage oil filled rad on a frost setting last night. I have never regularly opened the door during the day but admit it does help to give it an airing. At the moment there are too many variables with the weather etc. and leaving a heater on last night I will have to carry out some 'experiments' and measure the air moisture content both of the ambient air and that inside the motorhome and check against a psychrometric chart to see what the actual conditions are when the condensation forms. I am not really worried about this problem but originally brought this up to let others know that it is worth checking inside their MH's whilst they are laid up for or during the winter. We are lucky inasmuch as our MH is parked up on our drive behind the hedge and no problem to keep an aye on it. One thing I will do is take the silverscreen off for a while to see if that has any effect. Alan Link to comment Share on other sites More sharing options...
Brian Kirby Posted January 1, 2015 Share Posted January 1, 2015 AlanS - 2015-01-01 2:35 PM....................One thing I will do is take the silverscreen off for a while to see if that has any effect. Alan Why not Alan? My expectations would be that any condensation will then form on the consequently colder windscreen, and that the the temperature inside the van would drop further due to the loss of the insulating effect of the silver screen. I would add that "dry to the touch" is not necassarily a reliable guide. I seem to remember reading that the fire retardant grades of foam used in seat cushions etc are more hygroscopic than their non-retardant counterparts. The moisture lies within the foam, meaning that the surface may well feel dry while the core remains humid. That humidity would then be released to warmer air, and would probably condense onto rapidly cooling surfaces more readily than the foam would re-absorb it. I believe this idea underlies the often repeated advice to remove all such items from vans during winter storage. Be interesting to hear how you get on. Link to comment Share on other sites More sharing options...
lennyhb Posted January 1, 2015 Share Posted January 1, 2015 We had a strange build up of condensation last week, hope it was a one off to fluctuating weather conditions. The temperature change last week was a bit extreme, in one day daytime temps went from 13 deg to 4 deg and nighttime from 10 deg to zero. I think it was boxing, I day set the Truma Combi to turn on at 10:30pm, went back to the van at midnight dropped the cab bed down hopped up into bed to discover the roof lining soaked in condensation, not just wet but big droplets forming, luckily there was no quilt up there and the bed itself was dry. The bed had been fully raised which leaves about an inch air gap to the roof. Next night left the bed about 6-9" down no further problems. A bit worrying as we rarely use the drop-down bed & is normally left fully up, I would hate to drop it down one day & find a nice moldy mattress. Link to comment Share on other sites More sharing options...
Mel B Posted January 3, 2015 Share Posted January 3, 2015 The secret IMV is NOT to block out too much ... whilst we put external screens on ours over winter we do air it regularly and there is sufficient ventilation built in so we don't have any problems however I would NOT put cardboard on the side windows firstly because this this will 'cocoon' the interior even more so that the temperature doesn't balance with the exterior temperature and also because cardboard itself will hold moisture. I also wouldn't put a heater on in there as that won't actually get rid of the excess moisture permanently and a dehumidifier, whilst maybe useful to remove a large excess, won't stop some reoccurring as the van isn't a totally sealed unit so it will just come in from outside anyway. I would suggest leaving the external screens on but removing the cardboard and see if that helps. Regular airing, however, on a nice day would be the best bet though. Link to comment Share on other sites More sharing options...
StuartO Posted January 4, 2015 Share Posted January 4, 2015 Empirical adjustments will help, but I'm sure thekey to understanding and preventing condensation episodes such as the OP described is understanding the schoolboy physics which Brian has refered to. Motorhomes in storage are exposed to the very considerable climatic vairiations in temperature and also in moisture content of the air. Temperature and moisture content of the air vary independently, so we get damp and dry days which can be either warm or cold. An episode of condensation such as the OP reported could result from an unusual and fairly extreme climatic variation, when a warm/wet day turns into a cold but still moist night - the sort of night that produces a very heavy dew on your car. A motorhome full of exceptionally moist air cools overnight without drying out, so an unusual amount of condensation forms. Condensation always forms on the coolest available surface and in the absence of windscreen insulation, this will be on the inside of the windscreen. If silverscreens are in use it could be elsewhere, such as the roof above the drop-down front bed. Condensation is no respector of the privacy of nooks and crannies, and it seeks out the coolest surfaces regardless unless they are hermetically sealed spaces. So the condensation episode which the OP describes is nothing more than an exceptionally heavy internal dew. Just as an exceptionally heavy dew will evaporate outside, the condensate on the windscreen or the roof above the bed will evaporate too. As long as the surface material is not affected by getting wet the condensation should evaporate as the climatic change outside sorts itself out - and this evaporation of the condensation will happen more easily if air in the MH is free to circulate around the relevant area and as long as stuff like bedding or upholstery isn't in contact and hasn't soaked it up. Apart from ensuring that stuff like bedding and upholstery isn't in contact with the surfaces on which condensation might form and that air is free to circulate internally, exceptionaly heavy episodes of condensation of this sort are best left to sort themselves out, although you could obviously help things along by wiping the surfaces down to dry them off if you are inspecting the MH and come across heavy condensation. Although leaving some heating on might help to reduce the risk of this sort of exceptional condensation, it will increase the risk of vermin infestation to heat the stored MH. It would also be logical to leave silverscreens off when the MH is being stored unheated, since that would allow any exceptional condensation to form somewhere where it won't do much harm before it re-evaoprates. Have I got the physics right and does this all make sense Brian? Link to comment Share on other sites More sharing options...
Guest Joe90 Posted January 4, 2015 Share Posted January 4, 2015 Maybe better to ask a bloke at a bus stop, or a Climatologist. (!) Link to comment Share on other sites More sharing options...
Brian Kirby Posted January 4, 2015 Share Posted January 4, 2015 The warmer the air, the more moisture vapour it can carry. As our climate cools in autumn it is fed warmish, moist, atlantic air from which, as temperatures fall at night, the moisture tends to condense out. On clear nights horizontal surfaces will cool more rapidly than the air, and the condensation will form as dew. If the air temperature goes on to fall below its dew point, the moisture will condense from vapour to mist, or fog. The same is true of the air in the van, which is continually being changed via its permanent ventilation. Condensation on cold interior surfaces is inevitable when those surfaces fall below the dew point temperature of the air, which varies with the relative humidity of the air. So, it is a continually changing situation. If the day has been warm and the air relatively moisture laden, the air in the van will tend to be of a similar nature and, as the van cools during a cold night, the airborne moisture will condense onto whatever elements are below its dew point. There are basically two ways to counter this (there is a third, which would be to hermetically seal the van on a dry day, but hardly practical!). One is to dehumidify the air, the other is to keep the van interior just warm enough to a) maintain the humidity in the air and b) to keep the surfaces above its dew point. Dehumidifying seems to me problemmatic on two counts. First, most dehumidifiers become less efficient at low temperatures (because they rely on cold coils to condense the moisture, and at low temperatures the cold coils ice up), and second one has to dispose of the resulting condense. This could possibly be achieved by standing the dehumidifier in the shower tray and leaving the waste tank drain tap open, but still leaves the icing problem unresolved. I would not favour using the kitchen sink for this, as the condensate is fairly aggressive and may attack a stainless steel sink (plastics should be unaffected). Otherwise, one has regularly to empty the condense tray. An alternative would be to use chemical dehumidifiers, and many seem to find these effective, though they do need periodic draining and re-cycling. The alternative is to add some heat. It is a bit trial and error, because one is looking for just enough heat to prevent the temperature falling below dew point, but no more. This keeps the air that bit warmer, so maintaining its moisture bearing capability that bit higher, but also keeps the internal surface temperatures that bit warmer, so reducing the potential for condensation to form. Something like an electric greenhouse heater is ideal, as they are designed to prevent frost forming in greenhouses, and so have low temperature thermostats. Ours is 400W and the stat is adjustable, but not calibrated, so setting it is a matter of experimentation. As the weather gets colder into winter, and the air generally drier, I tend to creep the stat down to try to keep the van just a few degrees above ambient. I have not seen any sign of condensation over the 7 or so years we have had vans. I know others do nothing and don't get condensation either, but I'm more comfortable with the heater solution! I'm a bit uneasy about the idea of leaving insulting screens off to induce condensation to form on the windscreen, because I have no idea where all that condensate actually ends up when it rolls down the screen. It is inside the van, and somewhere near the dashboard electrics/electronics, which just makes me nervous! :-) Link to comment Share on other sites More sharing options...
kevina Posted January 4, 2015 Share Posted January 4, 2015 This is a question I also have; where does dripping windscreen condensation go? Is there a trap with an outlet into the engine bay or does it just settle somwhere until it evaporates? Link to comment Share on other sites More sharing options...
StuartO Posted January 4, 2015 Share Posted January 4, 2015 Brian, I can see that keeping a bit of heat going will reduce the risk of condensation inside a stored MH, indeed I said as much, but I'm not yet convinced that it is necessary to use heat for that purpose, and as I have suggested, heating the MH will increase the risk of vermin infestation during storage. (I've not suffered condensation problems personally but I have found evidence of mice getting, so I set traps and would be reluctant to make the MH more inviting to them.) I don't think you have addressed my theory that an episode of exceptional condensation, bad enough to get concerned about, arises primarily because of an episode of exceptional climate variation - although of course other factors such as poor MH design or build quality, leading to low wall or roof insulation values, could contribute to the risk or severity of the condensation. Heating, especially bliown air heating, can of course be useful as a temporary measure, eg to dry a MH out after an episode of condensation, but I don't think that makes the argument for using continuous, preventative heating as an anti-condensation measure. Accepted wisdom in the management of housing schemes used to be that adequate ventilation was a key requirement in the prevention of dampness and mould, even if it does put up your heating bill, although of course adequate wall insulation was prerequisite. I take your point about water running down the inside of the windscreen to goodness knows where and I thought of that, but I doubt that's a serious source of risk, or rather that it's a source of more serious risk than dripping condensation over the bed, such as the OP encountered. It would be nice to work out whether continuous heating is necessary for preventing condensation damage when storing a MH outdoors in a UK winter, I suppose that's the core of what I'm getting at. I bet companies like Hymer have researched this as part of their design efforts; pity they don't publish the results. Link to comment Share on other sites More sharing options...
AlanS Posted January 4, 2015 Author Share Posted January 4, 2015 Despite quite moisture laden air over the last few days and a return to the colder nights (-2 degrees C last night) I checked our motorhome this morning and it is perfectly dry and no sign of condensation. I haven't yet taken the silverscreen off yet as not had time but all is well again so far. I have always left cardboard across the windows of both our past caravan and motorhome windows as it saves having problems with the blinds - we don't like to leave them open either long term as it causes fading of the upholstery and soft furnishings. The cardboard is perfectly dry - if it had any moisture within it then it would tend to go floppy, which it hasn't. I will keep an eye on it and when we get back to the prolonged low temperatures below zero that we had had recently, I will take a few thermal measurements to determine the moisture content of the air and see at what point the surface condensation, if it returns, forms. Alan Link to comment Share on other sites More sharing options...
Brian Kirby Posted January 5, 2015 Share Posted January 5, 2015 StuartO - 2015-01-04 2:17 PM.....................It would be nice to work out whether continuous heating is necessary for preventing condensation damage when storing a MH outdoors in a UK winter, I suppose that's the core of what I'm getting at................. Despite waffling on about it, I'm not evangelical on the subject. Condensation is merely a risk. It's likelihood depends on the weather, which as we know is always changing. Given the wrong sequence of events condensation becomes likely. I prefer heating to nothing, and nothing to dehumidification, but those are my choices, based on my experience. Others have different preferences, based on their experiences. Whether anything is necessary will depend on how the weather deals the cards. Most of the time I suspect nothing is, so my little heater contributes nothing more than a bit of peace of mind - just in case. But, conditions are not consistent throughout the UK, so what works, or is desirable, in one place, is likely to be superflous, or wrong, in another. I don't think one should become didactic on the issue. If anyone experiences condensation in a van, they probably should do something between heat, dehumidification, or increased ventilation. If they don't experience condensation, they needn't really bother. If they merely want to avert the possibility for peace of mind, then I think gentle heat is probably the simplest, cheapest, way to secure that. But equally, it is probably unnecessary for most, if not all, of most winters. How about that for certainty? :-D Link to comment Share on other sites More sharing options...
PJay Posted January 5, 2015 Share Posted January 5, 2015 Fortuneatly for you Brian and ourselves, we live in a reasonably dry and warm area. I suspect that if you live further north or west it can be more of a problem. We do not have access to EHU where we keep our van, so all I can do is put the crystal dehumidifer in our van, but they don't get a lot of liquid in them , when I check , As some of you will know, we did have damp floor. which was replaced by Swift, since then the van is very dry inside, no mould ar damp now!! Or condensation. PJay Link to comment Share on other sites More sharing options...
StuartO Posted January 5, 2015 Share Posted January 5, 2015 Brian Kirby - 2015-01-05 11:39 AM StuartO - 2015-01-04 2:17 PM.....................It would be nice to work out whether continuous heating is necessary for preventing condensation damage when storing a MH outdoors in a UK winter, I suppose that's the core of what I'm getting at................. Despite waffling on about it, I'm not evangelical on the subject. Condensation is merely a risk. It's likelihood depends on the weather, which as we know is always changing. Given the wrong sequence of events condensation becomes likely. I prefer heating to nothing, and nothing to dehumidification, but those are my choices, based on my experience. Others have different preferences, based on their experiences. Whether anything is necessary will depend on how the weather deals the cards. Most of the time I suspect nothing is, so my little heater contributes nothing more than a bit of peace of mind - just in case. But, conditions are not consistent throughout the UK, so what works, or is desirable, in one place, is likely to be superflous, or wrong, in another. I don't think one should become didactic on the issue. If anyone experiences condensation in a van, they probably should do something between heat, dehumidification, or increased ventilation. If they don't experience condensation, they needn't really bother. If they merely want to avert the possibility for peace of mind, then I think gentle heat is probably the simplest, cheapest, way to secure that. But equally, it is probably unnecessary for most, if not all, of most winters. How about that for certainty? :-D Does this boil down to admiting that you don't realy know I wonder? :-D I came across this explanation of the formation of heavy dew, which i suspect is relevant. The water vapour content of a mass or air, and thereby the risk of condensation as the temperature falls, is clearly subject to fairly localised effects (they emphasise the importance of soil moisture in forecasting heavy dew) and so the particular circumstances in which heavy condensation will form inside a stored motorhome will include localised high moisture levels as well as low wind - and also whether the ventilation available to the motorhome will allow the internal air mass to equilibrate in the relevant timescale. Likewise, and perhaps more importantly for purposes of avouding damage from any severe condensation which does form in the exceptional climatic ircumstances I am postulating, how long it takes to dry out afterwards. I'm sure heating will alter the price of cheese quite a bit too (at the price of encouraging mice) but I think ventilation is also likely to have an important impact - especially on the drying out phase after some heavy condensation has formed inside a motorhome. Motorhomes are supposed to have plenty of ventilation (to prevent an accumulation of lpg from a leaky system getting dangerous) but I somehow suspect that would necessary be enough to clear heavy condensation such as the Op encountered quickly. I also think the exceptional climatic circumstances necessary for the formation of heavy internal condensation will mean that it doesn't happen regularly. Maybe the answer is to resist the temptation to use heat (to avoid encouraging vermin) and to ensure there ensure there is always adequate ventilation anyway - but to make a special effort to check the MH for condensation anyway after any episode of very heavy dew falling on the cars on the drive. Link to comment Share on other sites More sharing options...
StuartO Posted January 5, 2015 Share Posted January 5, 2015 The link missing from my previous post is: http://www.theweatherprediction.com/habyhints/4/ Link to comment Share on other sites More sharing options...
Brian Kirby Posted January 5, 2015 Share Posted January 5, 2015 StuartO - 2015-01-05 2:08 PM.........................Does this boil down to admiting that you don't realy know I wonder? :-D ........................ More or less, yes. :-D I think I understand the general principle, but on a day to day basis? So, I just leave the heater on over the colder months, and check inside from time to time. Been doing that since 2005, and not seen any signs of condensation yet, so either it works, or I missed it - or it isn't necessary! Not seen (or smelt!) any vermin either, but the van is left completely empty over the winter, so not much to attract them. I guess one could get a compact weather station and take avoiding actions when it indicates potential problems, but I can't see much benefit from going that far! So, I'm working on the KISS principle. :-D Link to comment Share on other sites More sharing options...
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