INSULATION vs CONDENSATION

[Tam_Hazan]

Over this winter we have used our boat as a floating cottage - the sailing bit comes in the summer!
However there have been significant condensation problems - and not just from the windows and hatches. The fibreglass hull seems to be wringing wet, both above and below the waterline.
What methods are there to combat this watery nuisance?
Thanks,
Tam Hazan

 

[Ecartar]

My next door neighbour had a similar problem. He has a ferro-cement boat of some 12M and lives aboard year round. With very limited insulation the problem has been solved by running a modest dehumidifier on 240v shorepower around the clock. When away from the boat the unit's outlet hose is placed in the sink. I understand the unit costs around £4/week to run paying 10p unit.

In contrast, the entire deck head of my 11M Dutch Steel Cruiser is insulated with 38mm sheet and the cabin sides above deck level forward with 19mm sheet. The sides of the hull in the engine room are also insulated with 'eggbox' foam rubber sound deadening. The remainder of the hull sides and wheelhouse cabin sides are not insulated. Despite large areas of glass above decks there is virtually no condensation when staying on board or when the boat is left unattended. The boat appears very warm at all times and requires minimal heating.

Regards,

 

[oldsaltoz]

G’day Tam.
Improvements to the ventilation will improve the situation, but if that fails you could glue a light felt fabric to the walls in problem areas.

Avagoodweekend Old Salt Oz……

 

[Trevor_swfyc]

Hi Tam

"Stop Breathing" sorry you are a new user so I'll have to take that back.
Condensation when the air becomes saturated with water, probably from your breathing hits a cold surface whereby it can no longer hold the water at the reduced temperature (its dew point) and result condensation.
What to do (1) Heat the boat to increase the airs ability to hold the water.
(2) Insulate the boat so that the air cannot contact a cold surface.
(3) Have a sacrificial cold surface, colder than the surface you do not want to have condensation on, the water will drop out preferentially on the colder surface. Basically this is a dehumidifier.
(4) Ventilation, ventilate the boat sufficient to avoid an increase in the humidity.
(5) Poke your head out of the hatch when you breath out.
Think this should solve it!
Breath easy summers coming.
All the best
Trevor

 

[PaulJ]

For what it's worth, I noticed in B&Q the other day that International make some stuff called "Anti Condensation Paint" for Bathrooms. God knows how it works - if indeed it does. I bought some to try out but I haven't tried it yet..... I'll try it this afternoon and let you know....... 'trouble is that I will have to take a bath to try it out and I had one of those last month.....

 

[Ohdrat]

Baths are V dangerous you can drown in them.. don't forget to wear your lifejacket and safety harness

 

[Piers]

Trevor is quite right.

The problem only really occurs during the cold months. For simplicity's sake, I would use small greenhouse heaters whilst I'm away, with a small de-humidifier on a 12 hour on, 12 hour off time switch. Heaters to keep the chill off, and the de-humidifier to dry the air.

Result? Good, clean air, no mildew, no damp, and smiles all round.

Small note - if you have lots of great teak, don't set the de-humidifier on too high a setting (too dry) since the wood may well start to dry out as well!

Piers du Pré
MBM Cruising Club enthusiast
www.dupre.co.uk/fsPlaydeau.htm

 

[PaulJ]

ANTI CONDENSATION PAINT - UPDATE

In previous Post I mentioned some International "Anti-Condensation" paint...

I applied two coats of the stuff to one half of a piece of angle iron which had previously been epoxy coated. Once it was dry I put it into the fridge to get nice and cold and then took it into the steamy Bathroom. Sure enough the half without the A-C paint quickly got condensation on it but the half with the wonder coating appeared to stay dry. It was possible to get condensation on it by holding it over a boiling kettle but that was a pretty severe test and I don't think you would do that too often with your boat!

It is a fairly thick paint, has a matt white finish and on the face of it would seem to be a miracle cure. However I think it is an acrylic based paint (low odour and you clean the brush in water) and couldn't vouch for it's durability under "marine" conditions. Why don't you try some on a small hidden area inside your boat and see how it copes after a few months of hot, cold, wet & dry salty atmosphere...... I suspect it might start to flake off.....

It is simply called "Anti-Condensation Paint" for bathrooms and kitchens and is made by International. I bought it in one of the big DIY stores, I think it was B&Q but it might have been Homebase...... Good luck!