Misting Up Side Windows

[kelly58]

When we were in Brittany the other week we were parked in bright sunshine which became very hot I noticed that as a shadow was cast across the habitation side window it started to mist up although the window is sort of double glazed with what looks like a couple of valves near the top of the window is this normal .

I have noticed mist spots before on the windows during rain spots but not like a large cloud across the inside if the cavity which took quite a while to clear .

[Basil]

Hi Kelly,

 

Yes we have had this on one of our caravan windows and it means there is some moisture between the two panes of perspex/ acrylic, whatever, that given the right conditions will condense onto the colder panel.

To cure you can wait until there is a very hot dry day and remove one of the bungs at the top then replace with a little sealant after it has had time to disperse, though this has limited effect and may well take in cold damp air at some later stage and it will appear again.

Alternatively I made up a system using an aquarium air pump and the clear tube associated with it passing the air through a baby's feeding bottle containing 'Indicating Silica Gel' crystals (available from any chemists) from one of the bunged up holes and returning to the other. this had the desired effect of removing the moisture completely (shown by the Silica Crystals no longer changing colour) and then replacing the bungs, exit one first to keep the dry air pumping in so not to introduce more moisture, and then the inlet one. The result was that we never had a further problem.

For us the 'tool' was made from bits and pieces laying about the garage so cost nothing but in any case it is not that expensive to buy all the componants, including the crystals which are reusable after heating up to remove the moisture from them at which time they return to their origional colour.

Hope that helps.

 

Bas

[Brian Kirby]

What you describe is quite normal, and the "valves" you describe are intended to allow the airspace between the panes to breathe.  After prolonged damp weather the air between the panes will have absorbed some atmospheric moisture and, when heated/cooled, this will cause slight misting on the cooler pane.  However, left to its own devices, and provided the edge seals between the panes are intact and neither pane is damaged, the heating cooling cycles will gradually "pump" away the moisture by the same route it entered, and all the misting will clear.