aluminium vs fibreglass

We have a Tvan and it is fibreglass. We did have problems with condensation on the inside of the Tvan and in the mornings sometimes you would get drips of cold water on you. If you touched the moisture, you would get runs down the roof. I ended up lining it with thickish material and that fixed the problem. I would imagine that you would get condensation on both aluminium and fibreglass - will have have a look at my window frames on a cold morning!
Andrew

We have an aluminium caravan on our property - and in winter time the condensation is incredible - it literally rains in the morning.

Condensation occurrs when there is a marked differential in temperature between the surfaces around you and the air in contact with them - and your breath (which is always warm - or should be ;) Moisture in your breath condenses as it cools from water vapour and co2 to water as it hits the cold surface - usually the roof as your warm breath rises.

Given all of this, I assume that reasonably thick fibreglass would provide slightly more insulation on a cold night from the outside air - so the inside surface temperature and air contained in the van would be warmer. If it's warmer then less of your breath's water vapour would condense into liquid.

Lining the inside of the van would only (I guess) "soak up" the condensation so that it didn't drip on to you as you snooze. It'd still be there though.

sepp5762

from what I remember, cold air holds less moisture then warm air. Thats why when warm air enters air conditioners and is cooled you get water as well. Or in reverse when you heat cold air it'll feel warm and DRY.

When the warm air in your van comes close to the cold walls or roof, it is chilled, like in an a/c, and the water droplets form.

The trick in preventing this is to insulate these surfaces so that the inside surface is not so cold and the air in the van does not chill. I imagine that fibreglass would be a better insulator then aluminium and therefore have less comdensation.

The best thing you can do is fit your own insulation which will also, as Chrispy said, absorb any water that may form.

I'm sure somebody on here in the A/C business will be able to explain this better then me.

Cheers,
R

I feel sure than a moisture absorbent layer is the go ("wicking" its called I think) - not one of insulation. Even a thick insulation layer will get damned cold on the freezing nights - a layer of material that the moisture can soak into, and evaporate from later, is the go. I'm under canvas, and we get some of this issue too, but with smooth impermeable surfaces it must be hell (as described). Its either the above or warm up the space with a heater !

One disadvantage of GRP (fibreglass) is that if it is finished in gelcoat, the gelcoat can have a quite short life in the Australian sun. it can deteriorate in a very short time if in the sun often or for long periods of time. This is why fibreglass aircraft such as sailplanes are finished in white (it reflects some of the damaging rays). If finished in two-pack like PolyU, then it will last longer.