Insulation Ideas

[Rich_F]

Having spent the last few weeks trying to track mysterious leaks, I've decided that I've got a condensation problem, resulting in puddles of water at the bottom of lockers after a night on board.

I guess the best solution is to attach some kind of non-aborbent insulation material to the inside of the hull. Has anyone tried this? What did you use, and did it work?

Thanks all,

Rich

PS I am also considering the alternative solution of a dehumidifier, plus shed-loads of extra battery capacity. But insulation would be preferable, I think.

 

[Guest]

Not Insulation, Ventilation!

Hi Rich,

Whilst I recognise that insulation can offer an excellent solution to condensation a better one is ventilation.
My boat had a big condensation problem when I bought her (The previouse owner kept a de humidifier on board 24x7x365). I have fitted three auto self closing Dorade style vents tothe coach roof. These allow a good flow of air thrpough the cabins and saloon and also help to extract the smells of cooking and the the heads.

We now only suffer from condensation when there are five or six adults and no heating on board (I use the boat as a sail trainer and often have five students plus me on board) Running the fan heater eliminates the condensation compleatly.

The Vents are excelent, they were desoigned for "Kingfisher" are self closing and can also be locked closed from inside the boat. Got them from Plastimo I think.

Hope that this helps.

Simes

 

[Anchorite]

Re:24x7x365: that was a very good year NM

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[charles_reed]

Richard,
Having had exactly the same problem when it was -8C outside and +22C inside the boat, I cured it by sticking aluminium/polystyrene sheet to the exposed deckhead.

Contrary to the poster who exhorted greater ventilation, I found leaving the locker doors open just added to the rate of condensation.

You can buy the stuff in rolls in any of the DIY sheds, sold to line the inside of external walls behind household radiators.

 

[richardandtracy]

Personally I favour both insulation and ventilation. If there is no ventilation you will always get condensation. Equally, if there is no insulation it'll be virtually impossible to cure the condensation however much ventilation you have.

How difficult is it to get to the dripping hull?
If it's not easy then I would suggest that you drill a few hiles in the back of units and fill the void with builders expanding PU foam (don't put in too much or it'll blow the back of your units in). This has the advantage of giving extra buoyancy for those rare occasions when the boat fills with water (oops, who took out the plug?). However don't use it on a wooden hull, as it'll rot. Also wear clothing while putting it in - if the stuff gets on your hands/arms it'll hurt like hell (been there, done that!).
Other areas, bonding on flexible radiator insulation etc. is a good idea.

Ventilation - go for 3-6 air changes an hour, any more and you'll be wasting heat, less and you'll start to get condensation even in an adequately insulated hull. What vent area for 3-6 air changes per hour? No idea! Try it & see, as it all depends on geometry, wind speed & direction relative to vessel.

Regards

Richard.

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[Guest]

Re:24x7x365: that was a very good year NM

Don't think I was on the right planet. Should have read 24x365x12x7. Oh Bugger just say it works all the time!

Simes

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[aztec]

mate of mine who lives aboard, recomends breathable felt. it's the new stuff they use on house roofs. stops water vapour from getting into the boat without limiting ventilation. he's lined the inside of his boat with it and panelled over the top, seems to work.

also he won't have anything shiney or with gloss surfaces in the boat, he says it attracts condensation. so all woodwork in the boat is waxed, or satin varnished. again it seems to work.

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[timevans2000]

All of this suggests that condensation/insulation is some sort of black art. It isnt. It is pure science.

in winter the outside air is cold. The relative humidity of this cold outside air is high compared to the air in the boat. If you raise the temperature of the outside air its moisture content doesnt change but its relative humidity (RH) reduces considerably. This is why you need good ventilation and heating in your boat. If you dont insulate your boat then this air you have just heated up comes in to contact with the cold hull ( at a similar temperature to the outside air) and its relative humidity rise again, to the point where it cant hold the moisture, so it condenses.

In summary, you need dry heat to warm the boat, insulation to ensure the boats hull is above dew point and ventilation to make sure that the air in the boat has a relatively low moisture content so it has the capacity to absorb more moisture from cooking, breathig etc

closed cell foam is very good as it stops the inside air touching the hull.

Here are some figures to make you think

if it is 20 deg C and 50% RH inside boat, your inside of the hull must be above 14 deg C to avoid condensation.

If it is 20 deg C and 70% RH inside your hull must be above 16.5 deg C to aviod condensation.

If it is 15 deg C inside and 50% RH your hull must be above 10 deg C to avoid condensation

These figures are not imaginary, this is fact and can be read off a chart. They do not vary.

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