Condensation again, sorry.

[Guest]

Don't know about anybody else, but this winter seems worse than usual for condensation!
Our boat, like many, has a stainless water tank under the cratch deck (which I will call the tank room), with a plywood bulkhead between the cabin and the tank room. The tank sits about two inches inches off the bottom plate.  I have never seen so much water build up in there before and honestly thought the tank had sprung a leak, or we were slowly sinking, but a mirror and torch under the tank reveals no obvious leaks anywhere. The tank runs with condensation when I have the step removed though. The hull sides and "roof" above tank are spray foamed, though there is a gap between tank and hull.
I will stop waffling now and get to the point;

I have today added extra insulation between the cabin and the tank room.

Is it worth fitting ventilation on the cratch deck above the tank, say a mushroom vent with a pc fan in it, to vent to outside (works in our bathroom)?
Is it worth lagging the tank where it is accesible and if so what should I use?
Any other suggestions most welcome.
Many thanks and season's greetings to one and all.

Edited December 21, 2018 by Guest
Fat fingers

[cereal tiller]

18 minutes ago, catweasel said:

Don't know about anybody else, but this winter seems worse than usual for condensation!
Our boat, like many, has a stainless water tank under the cratch deck (which I will call the tank room), with a plywood bulkhead between the cabin and the tank room. The tank sits about two inches inches off the bottom plate.  I have never seen so much water build up in there before and honestly thought the tank had sprung a leak, or we were slowly sinking, but a mirror and torch under the tank reveals no obvious leaks anywhere. The tank runs with condensation when I have the step removed though. The hull sides and "roof" above tank are spray foamed, though there is a gap between tank and hull.
I will stop waffling now and get to the point;

I have today added extra insulation between the cabin and the tank room.

Is it worth fitting ventilation on the cratch deck above the tank, say a mushroom vent with a pc fan in it, to vent to outside (works in our bathroom)?
Is it worth lagging the tank where it is accesible and if so what should I use?
Any other suggestions most welcome.
Many thanks and season's greetings to one and all.

Hi Stan

Putting a Fan in always sounds good but the best way to limit Water production is to stop Cold Damp Air getting Conductive with the Metalwork. Insulation alway good but not always worth the effort.

[cuthound]

My stainless steel tank under the well deck is insulated with sheets of 3M Thinsulate a d gives zero condenation.

[mrsmelly]

My tank is spray foamed. So was the one on my previous boat.

[TheBiscuits]

1 minute ago, mrsmelly said:

My tank is spray foamed. So was the one on my previous boat.

Inside or outside?

[mrsmelly]

Just now, TheBiscuits said:

Inside or outside?

I hate you to peices like meeces....................?

[Guest]

1 hour ago, mrsmelly said:

My tank is spray foamed. So was the one on my previous boat.

Yes wish I had done ours! Seems odd it has been OK up until this winter, but there we have it. I will get some insulation on it somehow! Thanks for replies and I can investigate further.

[blackrose]

6 hours ago, catweasel said:

 

I have today added extra insulation between the cabin and the tank room.

Is it worth fitting ventilation on the cratch deck above the tank, say a mushroom vent with a pc fan in it, to vent to outside (works in our bathroom)?
 

I'd think carefully before cutting holes in the bow deck because you might be compromising the water tight integrity of the deck and also fitting trip hazards with a mushroom vent..

[Matt&Jo]

Ours has done the same.......its not the end of the world we just keep the floor hatch open and a cheapy non powerd dehum bag thing in there seems to keep it sorted to a fair level

[blackrose]

6 hours ago, catweasel said:

 

I have today added extra insulation between the cabin and the tank room.

Is it worth fitting ventilation on the cratch deck above the tank, say a mushroom vent with a pc fan in it, to vent to outside (works in our bathroom)?
 

I'd think carefully before cutting holes in the bow deck because you might be compromising the water tight integrity of the deck and also fitting trip hazards with a mushroom vent..

[blackrose]

At least that's one benefit of an integral tank, as long as the bulkhead is sprayfoamed you don't need to worry about condensation. 

 

Why can't you just stuff rockwool in the spaces between the hull and the tank? Don't compress it too much. Then maybe a vapour barrier between the cabin and your rockwool insulated tank room. A sheet of foil lined celotex or kingspan would be perfect.

Edited December 22, 2018 by blackrose

[Guest]

10 hours ago, blackrose said:

At least that's one benefit of an integral tank, as long as the bulkhead is sprayfoamed you don't need to worry about condensation. 

 

Why can't you just stuff rockwool in the spaces between the hull and the tank? Don't compress it too much. Then maybe a vapour barrier between the cabin and your rockwool insulated tank room. A sheet of foil lined celotex or kingspan would be perfect.

Sounds like a plan. Rockwool would work well at the sides where there is very limited access. A vapour barrier seems an especially good idea. Thanks mike.

10 hours ago, blackrose said:

I'd think carefully before cutting holes in the bow deck because you might be compromising the water tight integrity of the deck and also fitting trip hazards with a mushroom vent..

Fair points.

10 hours ago, Matt&Jo said:

Ours has done the same.......its not the end of the world we just keep the floor hatch open and a cheapy non powerd dehum bag thing in there seems to keep it sorted to a fair level

Cheers at least I know I am not alone
The bag sounds like a good idea until I get around to sorting in properly. Costing me a fortune in nappies!

Edited December 22, 2018 by Guest