Condensation?

[DeanS]

I have a friend with a 40ft boat, and each week there's a few litres of water collecting in one back corner of the boat. The water pump isnt kicking in, so it doesnt seem to be caused by any water leaks. The water isnt soapy, so it doesnt seem to be from the shower. The waters quite clean.

 

Could it be condensation/water from roof/windows moving down the inside of walls..etc. Would you say a few litres a week is plausible in winter? We havent had that much rain, but the temps outside are almost freezing, and I think they're using heaters and the stove each day.

[Chris Pink]

No. Not plausible.

[Odana]

Given that my dehumidifier pulls over a litre a day out of the air even though it's only on a few hours, and that our walls and windows require a few teatowels wrung out to wipe em off each day, I guess his problem could be condensation, esp if boat has insulation gaps allowing it to condense and run down inside linings. Can he remove any panels to check condition of steel under?

 

This is all assuming he hasn't got a very) slow leak! If it is worse now than in summer, it's more likely condensation.

[BlueStringPudding]

The heavy rain of a few weeks ago, and melting snow can find their way in through leaking window frames and hatches. Add that to condensation and you can get a fair amount of clean water building up in the bilges. If it gets in near the front it can take a while to percolate through the ballast and and make its way towards the back of the boat, causing a delay to it appearing in that corner you mentioned. The other thing that could be causing clean water to appear is a small slow leak in the main water tank or the calorifier. If the quantity of water appearing remains quite high that is a possility.

[dmr]

This is scary but I am going to disagree with Chris Pink here.

A few litres per week of condensation is high but is certainly quite possible.

We have a trad style boat and sleep in the back cabin and a significant amount of condensation forms at the back, especially near the stern tube and fuel tank and also on the floor under the engine. Any exposed metal will generate condensation. My observation over the last few years is that it all kicks in very suddenly, I assume once the canal drops below some certain temperature.

 

.............Dave

[Joshua]

Ventilation is the key to preventing condensation, the average adult sweats a couple of litres a day (a lot more if you exercise) and it has to go somewhere.

 

 

[JDR]

I'm convinced that insulation is far more important than ventilation in preventing condensation. The cabin bilge on my boat stays bone dry throughout the year but in the engine room where the hatch is uninsulated and there are bare metal surfaces in contact with colder air the condensation this winter has been quite impressive.Maybe mop up a pint or two a fortnight.

[nb Innisfree]

I'm convinced that insulation is far more important than ventilation in preventing condensation. The cabin bilge on my boat stays bone dry throughout the year but in the engine room where the hatch is uninsulated and there are bare metal surfaces in contact with colder air the condensation this winter has been quite impressive.Maybe mop up a pint or two a fortnight.

 

Yes, insulation will prevent cold surfaces that condensation forms on, the moisture produced by sweating and kettles etc will stay in suspension.

 

ETA: All that ventilation does is to reduce the inside temp so that it is closer to the outside temp, effective but not very cosy.

Edited January 20, 2013 by nb Innisfree

[Biggles]

I think I cold very easily squigee 2L a week of the windows. I think I probably should save it. Free battery topup and steam iron water.

Edited January 20, 2013 by Biggles

[matty40s]

I have a friend with a 40ft boat, and each week there's a few litres of water collecting in one back corner of the boat. The water pump isnt kicking in, so it doesnt seem to be caused by any water leaks. The water isnt soapy, so it doesnt seem to be from the shower. The waters quite clean.

Could it be condensation/water from roof/windows moving down the inside of walls..etc. Would you say a few litres a week is plausible in winter? We havent had that much rain, but the temps outside are almost freezing, and I think they're using heaters and the stove each day.

Yes quite possibly Dean,(sorry Chris, I am going with dmr on this one) especially if they have windows with a channel at the bottom which has never been cleaned out. I moved a sailaway boat last week with an extrathick coating of sprayfoam, this had been cut back at some points to allow battens to be fitted, and the areas where the cut was too deep(ie, through to the metal) were weeping water. This was then sliding down to the bilge.

Edited January 21, 2013 by matty40s

[brian1042]

I have a friend with a 40ft boat, and each week there's a few litres of water collecting in one back corner of the boat. The water pump isnt kicking in, so it doesnt seem to be caused by any water leaks. The water isnt soapy, so it doesnt seem to be from the shower. The waters quite clean.

 

Could it be condensation/water from roof/windows moving down the inside of walls..etc. Would you say a few litres a week is plausible in winter? We havent had that much rain, but the temps outside are almost freezing, and I think they're using heaters and the stove each day.

 

I bought a dehumidifier and it is astonishing how much water I have to empty from it. In my view these are great value. Judging from this Forum, condensation seems to be a common boat problem.

 

Like your friend, I also had water that had collected. I got rid of the water and then used the humidifier. I think I can now tell which water is coming in via leaks.

 

BTW the humidifier is one recommended by people in this Forum and I am happy to share the name of the make and model. I am not being coy - I just do not have the info to hand.

Edited January 21, 2013 by brian1042

[Joshua]

 

 

ETA: All that ventilation does is to reduce the inside temp so that it is closer to the outside temp, effective but not very cosy.

 

Nonsense.

 

Cooling humid air inside the boat is exactly what causes the condensation, what has ‘equalising’ the air temperatures got to do with it?

 

When you open the door to a boat full of condensation (ventilate it) it dries up because all the humid air is replaced with drier air from outside, warm humid air leaving the boat is ‘replaced’ by incoming air not cooled by it. A given volume of air can hold a given amount of water, if you cool the air it can hold less, when it reaches 100% saturation (dew point) it condenses into water.

 

 

[Ex- Member]

I'm convinced that insulation is far more important than ventilation in preventing condensation. The cabin bilge on my boat stays bone dry throughout the year but in the engine room where the hatch is uninsulated and there are bare metal surfaces in contact with colder air the condensation this winter has been quite impressive.Maybe mop up a pint or two a fortnight.

 

 

 

Absolutely

 

We have reduced ventillation throughout the boat and especially through this cold period, the boat is lovely and warm and minimal condensation witth the bubble stove running on minimum and outtside temp at tthe moment -1. When we remove the port hole bungs (2 inch foam covered in faux leather) the glass is fully condensated, we simply wipe dry each porthole with a microfibre cloth as the bung is removed, this has become a riual every morning. The portholes stay condensation free for the rest of the day or until bungs are replaced.

 

Porthole bungs will save a lot of heat, on really cold mornings on removal there's been frost on the interior glass yet the boat interior is 19c+

 

Most the ventillation comes through tthe cabin doors & side hatch and the ventilation through the bilge supplied from vents in the cratch all, this ventilaion is lower down so much less heat is lost. Mushroom vents are far too big, ours are bunged but still leaving a small hole around 12 inch in each one. It's ridiculous to have ventilation that size at the highest part of the room/cabin as heat will simply rise directly and flow out, and not heat any of the boat. If you keep the boat interior at 19 to 20c + and he boat is properly insulated it should not condensate.

Edited January 21, 2013 by Julynian

[Joshua]

Absolutely

 

We have reduced ventillation throughout the boat and especially through this cold period, the boat is lovely and warm and minimal condensation witth the bubble stove running on minimum and outtside temp at tthe moment -1. When we remove the port hole bungs (2 inch foam covered in faux leather) the glass is fully condensated, we simply wipe dry each porthole with a microfibre cloth as the bung is removed, this has become a riual every morning. The portholes stay condensation free for the rest of the day or until bungs are replaced.

 

Porthole bungs will save a lot of heat, on really cold mornings on removal there's been frost on the interior glass yet the boat interior is 19c+

 

Most the ventillation comes through tthe cabin doors & side hatch and the ventilation through the bilge supplied from vents in the cratch all, this ventilaion is lower down so much less heat is lost. Mushroom vents are far too big, ours are bunged but still leaving a small hole around 12 inch in each one. It's ridiculous to have ventilation that size at the highest part of the room/cabin as heat will simply rise directly and flow out, and not heat any of the boat. If you keep the boat interior at 19 to 20c + and he boat is properly insulated it should not condensate.

 

Where do you think all the humidity goes then?

 

If you don’t vent it, your soft furnishings will have to soak it up instead, it has to go somewhere.

 

 

[Ex- Member]

Where do you think all the humidity goes then?

 

If you don't vent it, your soft furnishings will have to soak it up instead, it has to go somewhere.

 

 

 

 

 

Who said it wasn' vented.

[nb Innisfree]

Nonsense.

 

Cooling humid air inside the boat is exactly what causes the condensation, what has ‘equalising’ the air temperatures got to do with it?

 

When you open the door to a boat full of condensation (ventilate it) it dries up because all the humid air is replaced with drier air from outside, warm humid air leaving the boat is ‘replaced’ by incoming air not cooled by it. A given volume of air can hold a given amount of water, if you cool the air it can hold less, when it reaches 100% saturation (dew point) it condenses into water.

 

If the inside temp is equal to the outside temp then it won't be able to cool down any more which in effect is what you are saying. Condensation is caused by warm air meeting cold air, or, a cold surface, remove that differential temp and there will be nowhere for humidity to condense on and the best way to remove any cold surfaces and keep warm is with insulation.

[Justme]

If you are using LPG to cook, heat water or for space heating (using internally vented equipment) it is worth remembering that for each litre you burn you will release roughly about 700ml of water in to the air. Again roughly 1 litre weighs just under 500g. So for each 13kg bottle you are putting nearly 19L of water into the boat.

[bottle]

To stop condensation....

 

Hermetically seal all gaps, weld metal plate over all windows/portholes/mushrooms etc., insulate all surfaces with sprayfoam to a depth of 36" (100cms) and if that does not work fit a de-humidifyer.

 

 

I am sat here, boat at 23° C, all 'fixed' ventilation open and no condensation, we do get condensation but that is only on the pothole surrounds (brass), in the morning.

[Biggles]

This Linky is a nice litte PDF on how to overcome or prevent condensation.

[Joshua]

If the inside temp is equal to the outside temp then it won't be able to cool down any more which in effect is what you are saying. Condensation is caused by warm air meeting cold air, or, a cold surface, remove that differential temp and there will be nowhere for humidity to condense on and the best way to remove any cold surfaces and keep warm is with insulation.

 

I admire your imagination.

 

 

[nb Innisfree]

I admire your imagination.

 

Dream on.

[Joshua]

Dream on.

 

Even if you hermetically seal the boat as Bottle suggests and have every single surface spray foam insulated, the water vapour that you introduce through sweat and your cooking/heating appliances will not be reduced one bit.

 

All you are doing with insulation, is making sure that the relatively warm moist air, does not condense out onto a cold surface BEFORE you have time to VENTILATE it out of your boat.

 

As Julynian admits, his windows still get covered in condensation, that is because the warm moist air in his boat is getting to the cold surface of the window, if it didn't condense there, it would do it somewhere else, most probably on all your soft furnishings, mattress etc.

 

The only way to prevent or reduce condensation (other than avoiding introducing moisture in the first place) is to vent the warm moist air before it becomes saturated.

 

 

 

Edited for spelling

Edited January 21, 2013 by Joshua

[blackrose]

It depends on the level of insulation. If you heated the inside of a completely uninsulated boat it might produce a few litres of condensation, but the sweating steel would be completely obvious to anyone onboard, and since I very much doubt your friend's boat is uninsulated then I suspect he has a leaky window or other fitting. The thing to do is carefully check all lining for water stain marks.

 

Even if you hermetically seal the boat as Bottle suggests and have every single surface spray foam insulated, the water vapour that you introduce through sweat and your cooking/heating appliances will not be reduced one bit.

 

All you are doing with insulation, is making sure that the relatively warm moist air, does not condense out onto a cold surface BEFORE you have time to VENTILATE it out of your boat.

 

As Jenlyn admits, his windows still get covered in condensation, that is because the warm moist air in his boat is getting to the cold surface of the window, if it didn't condense there, it would do it somewhere else, most probably on all your soft furnishings, mattress etc.

 

The only way to prevent or reduce condensation (other than avoiding introducing moisture in the first place) is to vent the warm moist air before it becomes saturated.

 

That's not quite true.

 

While you are correct that insulation does not reduce the quantity of water vapour in the air, you are incorrect when you say that if it doesn't condense on a cold surface it will just condense somewhere else. Water vapour doesn't have to condense on surfaces at all - it can remain in the air, and the warmer the air the more water vapour it can contain.

[nb Innisfree]

Even if you hermetically seal the boat as Bottle suggests and have every single surface spray foam insulated, the water vapour that you introduce through sweat and your cooking/heating appliances will not be reduced one bit.

 

All you are doing with insulation, is making sure that the relatively warm moist air, does not condense out onto a cold surface BEFORE you have time to VENTILATE it out of your boat.

 

As Jenlyn admits, his windows still get covered in condensation, that is because the warm moist air in his boat is getting to the cold surface of the window, if it didn't condense there, it would do it somewhere else, most probably on all your soft furnishings, mattress etc.

 

The only way to prevent or reduce condensation (other than avoiding introducing moisture in the first place) is to vent the warm moist air before it becomes saturated.

 

I never said ventilation wasn't necessary, it's needed to prevent a build up of moisture but it can only reduce the humidity to the same level as that outside, but if a warm comfortable interior is wanted then all outside surfaces must be adequately insulated, the amount depending on how warm you want to be and the outside temp. We have brass ports that never suffer from condensation either on the glass or the brass and that's because they are insulated with double glazing. Mind you the space between both sheets of glass is ventilated otherwise it would have to be filled with an inert gas, (or an insulation material but I think that would defeat the object of ports)

 

Neither do we have condensation on any furnishings etc.

[Joshua]

It depends on the level of insulation. If you heated the inside of a completely uninsulated boat it might produce a few litres of condensation, but the sweating steel would be completely obvious to anyone onboard, and since I very much doubt your friend's boat is uninsulated then I suspect he has a leaky window or other fitting. The thing to do is carefully check all lining for water stain marks.

 

 

 

That's not quite true.

 

While you are correct that insulation does not reduce the quantity of water vapour in the air, you are incorrect when you say that if it doesn't condense on a cold surface it will just condense somewhere else. Water vapour doesn't have to condense on surfaces at all - it can remain in the air, and the warmer the air the more water vapour it can contain.

 

Within the norms of our real world and the temperatures we actually live in, the process of heat/expansion and rising dew point has a practical limit.

 

Given the amount of water a single adult sweats just sitting still, the air on a boat that is not ventilated, even if you have it as hot as a sauna, will either condense into water on a cool surface or leave some of its moisture on all your ‘spongey’ soft furnishings.

 

Of course, if you were cruising in an orbit close to the sun, in the vacuum of space then ……