Condensation on underside of mattress

[Charles Chodkowski]

Just returned from a few days away when i used an oil-fired radiator and a small fan heater and not the van's blown air heating system, so the garage was not heated (well we were on hook-up) on our return i found that there was considerable condensation on the underside of the mattress which is over the garage, what do members recommend that i use to keep the garage warm to stop this problem.

Thank you for your replies.

,

[colin]

well you could fit a 'green house' tube heater, this could be screwed to wall, you could vent the underside of matress/bed, or you could use the blown air.

[lennyhb]

Does the mattress sit on a solid base or slatted base, shouldn't get any condensation on a slotted base.

if a solid base there are two options one is something like Airmatt there are several similar products from various manufacturers our Hymer has this type as standard it appears to work OK, or a better option would be Froli Star .

[StuartO]

Lenny has hit the nail on the head; it is lack of air circulation under the materess which leads to condesation. Our 1990 Hymer had the matress on solid plywood, so it happened, the slatted bed frames on our 2006 Hymer prevent it completely.

 

Use your blown air heating, on gas if necessary, that will help too.

[Charles Chodkowski]

The mattress already sits on a slatted base.

[lennyhb]

Shouldn't happen on a slatted base unless air circulation is very poor. Froli Star can be fitted to slatted bases that would give a bigger air gap.

 

Or

 

Take off the plastic incontinence mattress cover. (lol)

[Minicamper]

We used to have this problem, but after recommendation on a camping website, we have no more problems. The solution was very cheap, a sheets of corrugated cardboard, placed under the mattress, to cover the damp areas. Lasted us a few seasons before we replaced them. We used opened out packaging such as tv or large appliance boxes.

[woody.]

This is a problem in static caravans as well when left over winter , the solution is to stand all the mattresses etc on end away from the bed bases so that air circulates around them and around the bed and seat bases . i prop them up against the cupboards etc , I do this every year and no problems yet , if you need to use the van then just put them back whilst you do . simples ;-)

[Charles Chodkowski]

It might help if people read the question before replying - I'm not asking about condensation whilst storing but whilst using.

[StuartO]

Thank you for telling us that you have slatted beds.

 

Presumably your slatted beds have an air space underneath, so on which surfaces is the condensation forming? Is it on the garage contents underneath the bed, because you have not been heating the garage?

 

If you have been reading the replies properly you will have seen the suggestion that you use the MH heating system as designed (i.e. circulating heated bloiwn air) to help resolve the problem. If your blown air heater only works on gas, consider investing in having your heater converted or replaced so it will run on electricity as well as gas if it doesn't already do so. Otherwise run it on gas, as designed.

 

You need the blown heated air circulating in a MH to avoid condensation on cold surfaces in unheated areas, in the same way you need either insulation on the windscreen or heated air flowing across the inside of the windscreen to prevent condensation forming there,

[Minicamper]

My reply related to a solution to the problem of condensation whilst using the bed. Should be worth a try, as it costs virtually nothing and it does work!

[lennyhb]

Surely cardboard will only absorb the moister and I would have thought make matters worse.

 

We have never used heating at night and never had any problems, current van the single beds at the rear we use most have solid bases with an airmatt type mat under the mattess.

 

Are you running you electric heating overnight? Hot air holds more moisture and if it is not getting distributed under the bed you will have a cold area for condensation to form, although condensation on the underside of the mattered is usually caused by body heat in the mattress and the underside not having enough air flow.

 

If you do need heating at night as Stuart says run the gas heating, it's cheaper to run than pay for an EHU.

I assume your van has a Truma Combi, might be worth fitting a CP-Plus controller it will give you very accurate control of the heating temperature & fan you can run overnight set at a low temp and fan is almost silent.

[Guest Joe90]

Charles Chodkowski - 2014-12-05 10:58 PM

 

It might help if people read the question before replying - I'm not asking about condensation whilst storing but whilst using.

 

So many variables, how much showering you did, how much cooking,kettles boiled etc, wet dogs and towels drying out, how much you ventilated the van, has it an extractor above the hob, or in the ablutions area , did you use outside silver screens as well, yes they largely eliminate condensation in the cab area, but that moisture has to go somewhere, do your roof lights have permanent ventilation, some do, some don't, our Rapido has a warm air outlet under the mattress, I guess it's there for a reason, and in cold weather we leave it open and the blow air system on low, and never get condensation on any of the soft furnishings............... :-)

[Corky 8]

Prior to buying our present Model of Motorhome, I did the usual reading up on the Pros and cons and one of the cons that came up regular was mould on the underside of the Mattress on the Garage type models, on checking the specifications on the model we were looking at it had a blown air heating outlet in the garage which the earlier models did not have and I thought this would cure the said problem, when we brought the Vehicle home and stripped everything out to do the Normal clean down of everywhere, I found a sheet of thin reflective insulation board the type you would put behind a radiator under the bed slats also I noticed a small mould mark on the underside of the Mattress, it was then I decided I would insulate the garage roof which was part of the bed base, I bought a sheet of 50mm 8x4 polystyrene which they use for insulating concrete floors, and cut it to the shape of the garage roof, I then gave it two coats of Fire retardant water base solution, once dry I stuck it in one sheet to the whole garage roof  thus far no more Mould. I do know there is an increased risk that should there be a fire in the garage it would flare up quite quickly once the flames took hold, but I do not consider us more at risk than any other motorhome, Not everyone's cup of tea I know.

[Brian Kirby]

This is quite simple. You have turned off the blown air heating in cold weather. Your garage presumably has a blown air duct feeding it - most seem to. With the heating off the garage is now cold.

 

OTOH, when you are in bed you, and to some extent the air in the rest of the van, are warm, and so your mattress will be warm.

 

While asleep, as at other times, you perspire. The perspiration will be, in part, absorbed by the mattress. So, you now have a warm, moisture laden, mattress sitting above a cold garage.

 

Commonly, the only separation between bed and garage is a sheet of uninsulated ply. So, whether or not the mattress sits directly on the ply, the top of the ply will be cold, and the moitsture trapped in the mattress will condense on that, and to some extent also within the lower, cooler, layers of the mattress.

 

This is the inevitable consequence of leaving the garage unheated in cold weather while the van is in use.

 

The only remedy is to heat the garage. So, as stated above, either use the blown air heating (making sure the blown air feed to the garage is open), or install supplementary heating in the garage.

 

Essentially, you need to reduce the temperature differential between garage and habitation cell to the practical minimum, so that the temperature of the (presumed) ply separation between the two does not fall below the dew point of the air in the habitation cell. Generally, leaving the blown air heating running will achieve this under any other than extreme circumstances.

 

Trying to achieve this by alternative means will be a matter of trial and error. Probably the best and safest solution would be a low wattage tubular heater mounted near, but not directly below, the ply, so that its warmth gets more directly to the ply, rather than merely heating the air in the garage and relying on that to warm the ply indirectly. If the heater is too close it will tend to generate a hot spot, which is not what you really want so, again, a bit of experimentation will be required. Ideally, the heater should not be too close to an end or side of the bed: a position near the centre, but biased towards the area beneath the trunk of your body would be best - though probably impractical to achieve. So, aim for the best achievable compromise with the ideal in mind.

 

Whatever heater you use must be installed so that it is protected from becoming covered by the contents of the garage, or you risk starting a fire!

[Will86]

I favour fixing insulation on the inside of the garage. There are a variety of materials, one is a roll of thin polystyrene with a mirrored backing plus there are many lightweight materials that builders use. All light weight easily fixed and out of sight.

 

Another moveable remedy is a sheet of 1 inch thick polystyrene on top of the garage. Obtainable from builders merchants.

[woody.]

Charles Chodkowski - 2014-12-05 10:58 PM

 

It might help if people read the question before replying - I'm not asking about condensation whilst storing but whilst using.[/quote

 

Just thought i would give you some usefull info , you obviously havent a clue .

 

It might also be a good idea to use your grey matter , brian kirbys answer is not rocket science .

[Charles Chodkowski]

Thank you Brian. I know why there is condensation and all I asked for was a few tips on what others had done when not using the vans own heating when on hook up.I will be fitting a protected greenhouse tube heater in the near future.

[StuartO]

Charles Chodkowski - 2014-12-06 11:02 PM

 

Thank you Brian. I know why there is condensation and all I asked for was a few tips on what others had done when not using the vans own heating when on hook up.I will be fitting a protected greenhouse tube heater in the near future.

 

So you had already worked out for yourself that using an oil filled radiator and a fan heater instead of the blown air system, thereby leaving your garage unheated, was what led to condensation, so all you wanted was suggestions for dealing with this problem, rather than using the blown air heating after all? So now you plan to carry a third electric heater with you, for use the garage, in the hope that will heat the garage sufficiently to prevent condensation?

 

The power you will need to heat the garage to balance thigs up will vary and a single low wattage tubular heater might not be enough. Perhaps several of them,with a thermostat controlling the power supply, will be needed, or a second oil-filled radiator or another fan heater.

 

And cluttering up your MH up with all this stuff and carrying the extra weight of it is all about maximising the use of electrical power from the EHU rather than consuming a bit of bottled gas to run the blown air heating system with which your MH is already fitted?

[Will86]

Insulating the garage from the body interior is better than putting a heater in there.

 

OK so it should prevent moisture forming on the top of the garage under the mattress where you sleep but although you believe you have a remedy you are avoiding the cause !

 

So when you're in the garage insulating its 'ceiling' you might as well insulate the wall that faces the van body as well for when any moisture forms on that its going to run down into the floor joints and cause a potential 'damp area'.

 

All the 'costly' energy you will be paying for in the garage will be transferring out the thin uninsulated body and door(s) in that section of the vehicle. What doesn't escape will produce buckets of moisture that will run down into the floor joints. Your choice to heat the garage is costly and not the best remedy.

 

Ps If you do insulate the garage then you can save energy by capping the hot air duct into it.

[Guest Joe90]

StuartO - 2014-12-07 10:37 AM

 

Charles Chodkowski - 2014-12-06 11:02 PM

 

Thank you Brian. I know why there is condensation and all I asked for was a few tips on what others had done when not using the vans own heating when on hook up.I will be fitting a protected greenhouse tube heater in the near future.

 

So you had already worked out for yourself that using an oil filled radiator and a fan heater instead of the blown air system, thereby leaving your garage unheated, was what led to condensation, so all you wanted was suggestions for dealing with this problem, rather than using the blown air heating after all? So now you plan to carry a third electric heater with you, for use the garage, in the hope that will heat the garage sufficiently to prevent condensation?

 

The power you will need to heat the garage to balance thigs up will vary and a single low wattage tubular heater might not be enough. Perhaps several of them,with a thermostat controlling the power supply, will be needed, or a second oil-filled radiator or another fan heater.

 

And cluttering up your MH up with all this stuff and carrying the extra weight of it is all about maximising the use of electrical power from the EHU rather than consuming a bit of bottled gas to run the blown air heating system with which your MH is already fitted?

 

To be fair, you'll be saving a couple of quid a day not using your gas. :-) :D

[colin]

If I was in OP's position I would proboly do the same, which is why I suggested it. If the van is insulated and one relatively small part is a cold pocket, then it makes sense to me to heat that part.

[Will86]

But why heat the garage at all, I see no reason, its a waste of energy.

 

Its like living in a house with 4 outside walls, one of which has a garage attached to it. Do you insulate 3 walls and windows only and heat the garage. Of course not !

 

 

[Guest JudgeMental]

I go along with Will on this + bed base needs redesigning allowing air to circulate freely underneath mattress. heating just a sticking plaster that does not address the real problem.

[StuartO]

The OP's MH is an A Class and isn't it likely that the garage will have the same sort of insulated walls as the rest of the MH? And isn't the blown air system likely to be necessary to keep the water tanks from freezing in winter too? It certainly is in my Hymer.

 

By all means use an electric heater to supplement the MH's own heating system but I can't see the sense in leaving the blown air switched off at all.