Condensation between 'skins'or layers of superstructure

[Cymraeg]

This year seems to be extreme in the formation of condensation on the underside of the flybridge cover, between the flybridge floor and the ceiling of the saloon, and the forecabin ceiling and the foredeck above. We do not suffer with any dampness within the body of the boat as we have ventilation and dehumidifiers, but these other areas are effectively sealed by the panels of the cabins and no air can get in. Haven't really noticed it much in the past, but this year there seems to be enough moisture that it runs down any sloping surface and drips into one or more living areas, usually a corner at the lowest point. There hasn't been any rain for a few weeks, although I have been on a wild goose chase looking for leaks. Sticking an endoscope camera through downlighter recesses showed that the top surfaces (i.e. flybridge floor which is a couple of inches above saloon ceiling, ditto foredeck above forward cabin ceiling) was dripping with condensation.

As these areas are effectively sealed, what can be done? I was surprised at the amount on the underside of the fly' cover as would've thought there were enough gaps for air to get through. Having said that it hasn't been that windy of late I suppose.

Anyone else had a problem, and maybe found a solution?

Thanks.

 

[Keith-i]

Heat and ventilation are the only real solution if you can’t improve insulation of the structure. You may think the void is sealed but in reality it will not be to water vapour.

 

[rafiki_]

Ventilation is your solution.

 

[Cymraeg]

Ventilation is your solution.

Yeah, thanks, but I suppose the crux of my question is how? We know about ventilating the main body of the boat as all soft furnishings remain in situ without any dampness, mould or any other nasties. I don't recall any threads where people add vents into their headlinings ..... or perhaps I've just missed them. I suppose the other solution may be to carve holes in the exterior body and add vents, but similarly, do other manufacturers do this?

1999 Sealine T46 btw.

 

[rafiki_]

On my Azi there was a vent in the foredeck above the fwd cabin. Quite normal on this type of craft? I wouldn’t go carving holes. Have you tried a good blast with a dehumidifier?

 

[A_8]

"Condensation management" should be part of the design as should ventilation. On the boats I have had experience with there have been two parts to the air inlets, one for the engine and the other for the rest of the boat. There has also been a inner shell under the superstructure with a few centimeters of space for air circulation and insulation, keeping condensation from forming on the cabin surfaces with a water collection design at the lowest parts draining into the bilge.

I suggest you try to figure out how this is supposed to work (or not) on your boat and then decide if you go for making sure there is really good ventilation or you try to "seal" the boat and use dehumidifiers to keep the air dry enough not to condensate.

 

[oldgit]

Observations over this UK winter about more than usual quantities of condensation inside boats, not just in the cabins but in bilges.
A highly technical and advanced analysis of the water proved it to be fresh not salt, a task not to be undertaken lightly when sampling the liquid underneath the black water holding tank ?

 

[Seastoke]

You could pop out the spots , and let the dehumidifier get at it.

 

[Greg2]

Observations over this UK winter about more than usual quantities of condensation inside boats, not just in the cabins but in bilges.

Thats interesting - we were out with boaty friends on Friday night and I commented on how dry our boat felt this winter - haven’t had the de-humidifier running for two or three weeks and having put it on it cut out after a couple of hours and rarely ran the rest of the time we were aboard. They reported the same. I did notice some condensation in the engine bay though.

 

[oldgit]

I did notice some condensation in the engine bay though.

 

[Cymraeg]

Observations over this UK winter about more than usual quantities of condensation inside boats, not just in the cabins but in bilges.
A highly technical and advanced analysis of the water proved it to be fresh not salt, a task not to be undertaken lightly when sampling the liquid underneath the black water holding tank ?

This was my observation also, never seen it so bad. Perhaps because the weather has alternated between cold then wet & mild? I have removed some of the ceiling panels and the backing board does have a few old water marks so it has occurred before, but never on this scale. Location a factor too no doubt, as little snow in the South West.

Thats interesting - we were out with boaty friends on Friday night and I commented on how dry our boat felt this winter - haven’t had the de-humidifier running for two or three weeks and having put it on it cut out after a couple of hours and rarely ran the rest of the time we were aboard. They reported the same. I did notice some condensation in the engine bay though.

Yes, conversely from my comment above and I think said originally, the interior of the boat i.e. mattresses, cushions etc. have been perfectly dry. I stay aboard regularly throughout the winter and whilst it's been f-f-freezing cold, never damp. Except obviously where condensation has accumulated and formed drips in a few localised areas.

You could pop out the spots , and let the dehumidifier get at it.

This is ace and exactly the kind of stuff sought on forums like this, just kicking myself now that I didn't think of it. Quick, simple, cheap and probably the most effective although as the weather has changed (again) might be a little while before I can prove it. I think we'll have to get into the routine of popping out the spots late autumn every year and leave them out 'til spring - if we want to use the boat easy enough to pop them back in. Cheers!