yacht insulation and condensation

S

strawbs3

New Member
Joined
10 Nov 2009
Messages
13
Location
North Devon
Visit site
I've got a 1970's 32 foot double diagonal mahogany ply, grp on the outside yacht. It has no insulation at all. We're living on it all year round and now winter's comming we're having a nightmare with condensation. I've been looking into insulation but got myself all confused; if using something like celotex should you leave a gap behind it or not? Should it be stuck with glue to the wood, or is it ok to just put the celotex in snuggly then cover it over with ply? I'm using celotex as it seems to be the cheapest, easiest and less messy option. Any one help please?
 
rot

I don't know much about insulating a wood boat. However, it seems to me your scheme would trap moisture against the hull, creating a kind of rot farm. Plus, you'd loose sight of your planking and it's condition.
 
strawbs3 said:
I've got a 1970's 32 foot double diagonal mahogany ply, grp on the outside yacht. It has no insulation at all. We're living on it all year round and now winter's comming we're having a nightmare with condensation. I've been looking into insulation but got myself all confused; if using something like celotex should you leave a gap behind it or not? Should it be stuck with glue to the wood, or is it ok to just put the celotex in snuggly then cover it over with ply? I'm using celotex as it seems to be the cheapest, easiest and less messy option. Any one help please?
Click to expand...

Ventilate during the day, heat with a solid fuel stove in the eve, and fan blowers first thing in the morning.

Its a small space and you have to let the moisture out from breathing and cooking so ventilate ventilate etc.

Any insulation on a boat of that type will turn it into a valueless rot box.

A ridge pole and cover to keep frost (?) off the deck helps enormously too.

I lived on a similar boat for 9 yrs and this worked for me,
 
celotex

we live on a plastic boat all year i have insulated with celotex it condensates betwween hull and insulation not a problem for us as it runs into bilge have found bubble rap good
 
I remember my electronics lecturer's advice - "Earth everything, and insulate everything else".

it's similar on a boat: Ventilate everything, and insulate everything else.

It's true. I moved into a flat in Chalfont St Peter with a wonderful in-wall larder. "Oh, don't use that", said the landlord, "it's full of mould".
So it was.
Later, inspection revealed a rear window light, tightly closed. Experimentally, I opened the light and cleaned off the mould. It never came back. The larder was absolute magic.
Ventilation is the key. Anti-condensation paint will help in non-ventilated, cool corners.
A great enemy is combustion - cooking and heating both provide vast amounts of moisture.
Another enemy is the human being - a useless creature which exhales copious amounts of moisture. It also sweats, perspires, and a la Sam Goldwyn, glows, moisture.
 
... and I will repeat what the others have said. Ventilation is the key.. Always having air blowing through the boat at some point in the day... If there's a hatch you can leave ajar without getting rain in then even better... Even go so far as to lift the mattress slightly each morning (if it's resting on solid locker tops) .. and put something under it for the day to give that air underneath... Some suggest slats under the mattresses.. but another thing is the under mattress insulation that's about £75/ sheet.. about an inch thick and nearly all air.

Warm air blown heaters (e.g. Webasto / Eberspacher) are also good in that they will bring new air into the boat therefore pushing colder damper air out.

If you do go for an insulation then perhaps moving air behind that is again useful.. to keep it fresh behind.
 
You could always line the visible parts of the hull with a ceiling - narrow wood slats with a small gap in between them. This will allow air flow behind them against the hull and any thing that touches the ceiling slats won`t get wet. I am doing this to my boat but because it is fibreglass I will put closed cell insulation behind the slats. You want your hull to get fresh air so insulation is a bad idea.
 
Last edited:
Thanks very much to everyone for all the info. Looks like the first step is ventillation so i've asked santa very nicely for some dorade boxes and vents. We're also going to bite the bullet and put a log burner in. Luckily my boyfriend makes them so he can do a lovely one- we just didn't really want to go chopping holes in the deck or coach house for flue; but it's got to be done as in the forepeak it's getting nasty. As for the insulation i'll leave that for now and see how the other two solutions work. I'd rather be able to keep an eye on the hull's condition than cover it up.
thanks again for all your help.
Hope everyone has a splendid Christmas
steph :D
 
Just a thought, but we recently bought a dessicant type dehumidifier and reckon it was the best £150 we have spent. Dry air all the time, no condensation, everything feels fresh and dry. Also, if you are thinking of helping the bedding breathe, try Ikea bed slats cut to size and placed under the mattresses.
All the best,
Chris
 
You must log in or register to reply here.

Share this page

Top