Anyone run their heater when caravan not in use?

[Dustydog]

Whoops just crossed with the Profs
I’ll correct later DD

OK clearly I am using faulty logic here; so here are my “workings out”. Which step is sending me in the wrong direction.
1. Using a dehumidifier immediately after using the van will remove the moisture generated by use ( breathing, showering etc). Thus the van now contains less moisture than before I used the dehumidifier.

Just opening the door and then closing it will in most cases equalise the caravan humidity to the outside

2. When the van is not used, over time the moisture inside increases due to airborne ambient moisture.

Not quite. I doubt the internal moisture will exceed that in the ventilated ambient air.

3. Even with some ventilation the moisture will increase over time as it is trapped in the van so that it rises above external ambient.

Unless you have water ingress, adequate ventilation will halt moisture build up.

4. Deployment of a dehumidifier for a fixed period will reduce the moisture content to below external ambient especially in a small 2 berth such as we have as the dehumidifier will remove moisture faster than it is getting in.
Steps2, 3 and 4 repeat over storage time.
Outcome: the moisture content of the van is managed to be at or below ambient for considerable portions of storage time.

Couple of caveats; our van is not on the driveway so cannot try this- it is a thought experiment ( Shrodinger’s dehumidifier 😀)
Also not read any peer reviewed papers that experimentally demonstrate results.

Thoughts?
Mel

There seems to be some misconception regarding exactly what a dehumidifier does, and how moisture is related to humidity.

Humidity is the amount of water vapour, an invisible gas, in the air. Warm air can ‘hold’ more water vapour than cold air; in fact, air at 35°C can hold six times more water vapour than air at 5°C. Probably the opposite to what most believe.

Mould is an airborne spore that thrives in a specific set of circumstances.Lack of ventilation is the primary cause rather than the ambient temperature. The dehumidifier doesn’t change the temperature.
More importantly I have found the best deterrent for Mould is wiping down all hard surfaces with a cloth that has been rinsed in a 10% bleach/ water solution. The spores don’t like the treated surface and won’t germinate.

Hope I haven’t spoilt your day Mel but I am not a fan of the dehumidifier as I don’t believe it achieves the results you seek

 

[JTQ]

I when we winter caravanned, used the dehumidifier on our return from trips to strip the damper, habitation state air of some of its water and lower the moisture in those items like soft furnishing that absorb moisture.

With our refrigeration system based Mitsubishi domestic unit, it is certainly not true they don't warm the air, it using that technology is actually quite an effective low level heater.

I would also use it through the night before we made cold winter trips, so that all was both a bit drier and warmer, better "aired" than it might otherwise be.

It is very good at drying laundry, so quite clearly it does reduce the moisture held in fabrics, along with I accept attempting to dry out Hampshire.

 

[Mel]

Thank you all for going through my workings out.
As I said it is a thought experiment in my case as the van sits happily in storage and we have had no problems with mould or condensation with little or no intervention from us above the usual sensible stuff of leaving lockers open and what have you.
Also, no worries DD, being incorrect has never spoiled my day. There is nothing better than new learning ( also after nigh on 40 years in the NHS and 15 years of fostering I am almost impossible to offend 😀)
Mel

 

[otherclive]

I when we winter caravanned, used the dehumidifier on our return from trips to strip the damper, habitation state air of some of its water and lower the moisture in those items like soft furnishing that absorb moisture.

With our refrigeration system based Mitsubishi domestic unit, it is certainly not true they don't warm the air, it using that technology is actually quite an effective low level heater.

I would also use it through the night before we made cold winter trips, so that all was both a bit drier and warmer, better "aired" than it might otherwise be.

It is very good at drying laundry, so quite clearly it does reduce the moisture held in fabrics, along with I accept attempting to dry out Hampshire.

We use a dehumidifier in the bathroom to dry laundry. It’s slower than tumble drying but cheaper and gives out a surprising level of warmth into the bathroom.

 

[Buckman]

Whoops just crossed with the Profs
I’ll correct later DD


Just opening the door and then closing it will in most cases equalise the caravan humidity to the outside

So using a dehumidifier which collects the 1 litre of water and then opening the door to remove that 1 litre adds the 1 litre of water back into the caravan. Seems to be going around in circles? LOL!

 

[izzy]

Seems to work for me, and I don't use it enough to break the bank so what's the harm?

 

[otherclive]

Seems to work for me, and I don't use it enough to break the bank so what's the harm?

There’s absolutely no harm if that’s your preference. Although the “greens” may think otherwise.

 

[Dustydog]

There’s absolutely no harm if that’s your preference. Although the “greens” may think otherwise.

Not if it’s heat pump driven😉

 

[otherclive]

Not if it’s heat pump driven😉

I think it’s still a waste of time and electricity. But as one said “ each to their own”

 

[Mr Plodd]

Do manufacturers and dealers use heaters and/or dehumidifiers in their caravans that are left outside for many months?
The answer to that question is no, which should tell you all you need to know about the necessity/desirability of using either or both.

 

[ProfJohnL]

If you have a caravan that does become damper when in storage, then perhaps the caravan has some leaks. You should investigate where the damp is coming from. That should be a priority. Cure the problem not the symptom

 

[Dustydog]

So using a dehumidifier which collects the 1 litre of water and then opening the door to remove that 1 litre adds the 1 litre of water back into the caravan. Seems to be going around in circles? LOL!

You may know it as litres in the wind😉

 

[JTQ]

Do manufacturers and dealers use heaters and/or dehumidifiers in their caravans that are left outside for many months?
The answer to that question is no, which should tell you all you need to know about the necessity/desirability of using either or both.

IMO that take has way more confidence in caravan manufacturers and dealers opting to do the "right thing" for the end user than I have!

 

[Sam Vimes]

Do manufacturers and dealers use heaters and/or dehumidifiers in their caravans that are left outside for many months?
The answer to that question is no, which should tell you all you need to know about the necessity/desirability of using either or both.

Sorry but that's the wrong question. It should be how many dealers sell their vans with existing damp problems. Mine had a damp problem that must have existed when it was on the forecourt. Searching suggests I'm not the only one.

Equally they sell vans with all manner of problems that shouldn't exist in a new van.

 

[Sam Vimes]

I'm not surprised that my original question provoked the perennial questions and answers but here's my reasoning.

The climate around the UK varies and the problem of condensation and mould may well vary. In my area and regardless of precipitation and temperature, the humdity can be very high. In the last few weeks when we've had a mild November with temperatures around 12/13degC the humdity has still be up in the 90s. Then a couple of days back the temperature dropped quickly to 4 and below. The humidity went as high as 99% but my weather station only has two digits so it could have been 100%.

With the insulation properties of a caravan being equivalent to a piece of lettuce the inside temperature also dropped fairly quickly. So with the high humidity and low temperatures these are ideal conditions for condensation to form. So, I thought why not run the heater and see if I can hold off the formation of condensation - and it did. (This is what you do in your car to demist the windows). Well in most areas it worked because the air flow around a caravan isn't that uniform

However this solution isn't really feasible. It would be costly to run and as mentioned there would be areas in the caravan and surfaces that would still be cool enough for condensation to form.

The usual suggestion of good ventilation works to some degree. Ventilation is supposed to reduce condensation and hence mould formation by trying to get the high water content air flowing around and being replaced by air with less water content. This might work when you're trying this at home, say in the bathroom, where the extracter throws out the high humidity air and replaces it with better air from the rest of the house. In a caravan like mine and I suspect yours, sitting in a high humid environment all the time, the ventilation is just replacing high water content air with the same. Plus the natural ventilation air flow isn't going to reach all parts.

The only thing I can do is make the natural ventilation reach as many regions as possible, so the inside looks like its furniture showroom that's been vandalised. I've still noticed a view regions - the entry door for example - that are showing a few black spots. They clean off easily.

 

[izzy]

I am not saying that dehumidifiers are a cure all, not even sure of the benefits really!
but the van is 12 years old and dry and I will do anything to try and keep it that way.
OH says that it is a shame that I can't knit it a pullover

 

[Mr Plodd]

A heater or dehumidifier will not stop/cure any leaks!

 

[ProfJohnL]

As Sam points out the propensity of conditions that can produce condensation does vary all over the country, but the mechanism for it to arise is the same wherever you go. and the methods of dealing with it when ot does occur should be the same.

Just be aware that there are two ways of of quoting the humidity which if its not defined can lead to misinterpretation.

I suggest if you want to know the difference methods see here

 

[Sam Vimes]

Most weather reports use Relative Humidity as a measure of water vapour held in the air. When discussing condensation Dew Point may be more appropriate but I don't ever recall seeing values for it in weather forecasts.

We've also discussed the fact that for the same volume of air, warmer air can hold more water vapour than colder air.

Condensation forms when the air temperature drops which means the volume of air has to lose some of the water vapour. The temperature at which this occurs is the Dew Point

 

[Stevejj]

I thought that as we're not using the van in the winter months and it's parked up at home I'd run the heater for a few hours every month or so during the damp winter season. Might just keep damp and mould at bay.

Hiya, I know you can have the heating on through winter but I never have. What i tend to do once we have finished touring for the season is first jack up the van so the wheels are off the ground, after washing put on the breathable cover then fully clean the interior ready for next season. Around November/December I get two small washing up bowls and fill each bowl with dish washer salt that I purchase from Tesco put one on the floor in the lounge area and the other in front of the bath/shower room with the door open, I find this one normally collects more moisture due to the mushroom vent in the shower ceiling, once a month I go in the van and stir the salt to see how much moisture is at the bottom of the bowl, sometimes swoping them around, I may have to replace the salt once between December and February according to how bad winter has been. I've had the van from new (2017) and have never had any damp issues, damp readings have always been brilliant when van has been serviced by my mobile engineer. The salt is not wasted as I put it into a rubble bag and leave it open to dry out and then use it in my dish washer.

 

[ProfJohnL]

Hello Steve,
What you are doing is simply removing a small proportion of the moisture from the air which is constantly passing through the caravan becasue of the fixed ventilation. You're not actually making any significant difference to the moisture content of the caravan.

At least the cost of your attempts is minimal, and you're doing no harm, but if it makes you feel better OK, but i'm sorry, it simply doesn't work.