condensation and air gaps!

[Dave Payne]

Next to my bed is the wall, behind this is foam insulation then steel, I get terrible condensation in the colder months usually resulting in wet quilt on one side.

 

If I was to put some thin battons on top of the existing panel then put another panel of thin ply over creating an air gap, would it reduce/stop the condensation?

 

I plan to store the extra mattress that will extend my bed in this space, on its side tucked under the gunwhale so really need to ensure it stays dry.

[The Bagdad Boatman (waits)]

do you get condensation on the foam insulation?

[Murflynn]

If you are getting condensation on the wooden (?) surface of the wall which contains insulation, then there is something seriously wrong. Is there a window involved? Is there a gap in the insulation allowing a cold spot to arise in the colder months?

[Dave Payne]

I would need to remove the panel to see whats happening behind, i do know on other parts of the boat the gap between panel and foam insulation is about 5-8mm.

 

When i say foam, its the white sheet stuff, not spray foam.

[WotEver]

When i say foam, its the white sheet stuff, not spray foam.

Polystyrene panels? Just loosely fitted?

[Dave Payne]

Polystyrene panels? Just loosely fitted?

 

 

yup.

[lampini]

Obviously you need to get in there and fill in all the gaps which you will find IMHO will be behind the paneling.. Sadly my arthritis makes me like the princess and the pea - my knees and hips will detect the smallest amount of damp (and an incoming rain front too!)!

 

We put a layer of this

 

http://www.practicalsurfaceware.com/anti-moisture-mattress-underlay-airmat.html

 

under the bed and also up the side too.. not cheap at £60 for a double size but worth it i'd say..

 

Now the moisture collector under the bed has about two drops in it at last inspection rather than the half a container we had before, my hips and knees are happier than they were in the house last winter!

[WotEver]

yup.

As above really. I suggest you pull off the lining (I appreciate this probably won't be a light undertaking) and use some spray foam to fill all the gaps.

[Dave Payne]

sounds like a plan, should be able to get the panel off quite easily really, just a few screws, if they are not rusted!

 

If the sheets of foam have slipped, i guess it would be a good idea to ensure they are back against the steel with a decent air gap between them and the wood panel?

[WotEver]

sounds like a plan, should be able to get the panel off quite easily really, just a few screws, if they are not rusted!

 

If the sheets of foam have slipped, i guess it would be a good idea to ensure they are back against the steel with a decent air gap between them and the wood panel?

Yup. Assuming that spray foam doesn't melt them (anyone know?) then you could use little blobs of it to stick the panels to the hull.

[BruceinSanity]

Yup. Assuming that spray foam doesn't melt them (anyone know?) then you could use little blobs of it to stick the panels to the hull.

And when you've done all that and put the panel back, covering it with carpet tiles will make it even warmer to snuggle up to.

[Neil2]

Condensation is a swine isn't it. We have a spot on the cabin ceiling which in the winter creates a drip about once a minute and it can only be a small gap in the insulation. One of these days I will have to tear away the T&G to get at it, I think it's about #163 on my to do list.

[Dave Payne]

i have one of those spots also, on the front bulk head, right above where i hang my robe, getting the panel off is not as easy there though...

[Taslim]

i have one of those spots also, on the front bulk head, right above where i hang my robe, getting the panel off is not as easy there though...

I had similar on a panel and one part of the roof lining on the truck.

 

As a 'just for now' in summer I drilled 1/2" holes where the prob was and injected Mokey Sp....Feb Foam into them. Still good afrer six years.

 

Don't bang in to much. The foam realy expands!

[Bee]

And when you've done all that and put the panel back, covering it with carpet tiles will make it even warmer to snuggle up to.

I,ve even had condensation on carpet tiles, condensation is a real sod. I would remove as much panelling as possible, put in another inch or two of polystyrene, fill every little gap with spray foam and then see if you get condensation on the polystyrene, if you do then stick another inch of poly on, when you get a dry surface then put everything back together and think about ventilation and heating. I have had condensation probs. in the past that I never did solve. I have always used basic radiators and back boiler heating with gravity circulation because it needs no pump but if you want rads all around the boat on both sides then that could perhaps solve the problem but you will need a pump. A narrowboat is a difficult shape to heat and ventilate.

[Murflynn]

I,ve even had condensation on carpet tiles, condensation is a real sod. I would remove as much panelling as possible, put in another inch or two of polystyrene, fill every little gap with spray foam and then see if you get condensation on the polystyrene, if you do then stick another inch of poly on, when you get a dry surface then put everything back together and think about ventilation and heating. I have had condensation probs. in the past that I never did solve. I have always used basic radiators and back boiler heating with gravity circulation because it needs no pump but if you want rads all around the boat on both sides then that could perhaps solve the problem but you will need a pump. A narrowboat is a difficult shape to heat and ventilate.

I don't think it helps much to increase the thickness like that.

 

The laws of physics tell us that increasing insulation thickness is a matter of diminishing returns.

If one inch of polystyrene suffers from condensation then there is something very wrong in the environment inside your boat, and adding another inch shouldn't make any noticeable difference.

 

Also hard to believe you can get condensation on carpet tiles, unless they have very short pile, because they hold an air layer that is kept relatively warm by the boat heating.

[Taslim]

I don't think it helps much to increase the thickness like that.

 

The laws of physics tell us that increasing insulation thickness is a matter of diminishing returns.

If one inch of polystyrene suffers from condensation then there is something very wrong in the environment inside your boat, and adding another inch shouldn't make any noticeable difference.

 

Also hard to believe you can get condensation on carpet tiles, unless they have very short pile, because they hold an air layer that is kept relatively warm by the boat heating.

A very good point.

 

I assumed (I know assumption is the mother of all cock ups) that there was a local breach in the insulation so a local fix would do so m'be we need more info about the boat.

[Bee]

I got condensation on carpet tiles that were glued to the thin ply lining on the hull sides right down just above the floor and below water level. The insulation was 2" polystyrene, most of the boat was fine but it was right at the back of the boat in a badly ventilated bedroom, I never really managed to solve it, couldn't get much heat back there and couldn't ventilate it very well, I've never had much problem with sprayfoam but if you have solid ice on the other side of a steel hull and then a couple of inches of foam and ply its asking a lot of any insulation. I would hazard a guess that at least 4 inches would be a minimum, probably more but you would end up with a very narrow narrow boat.

[Murflynn]

as I said, much more likely to be the result of unsuitable environmental conditions INSIDE the boat, rather than the presence of ice on the outside.

 

If 2" of polystyrene does not achieve the necessary level of thermal insulation to prevent condensation, then it is highly unlikely that 4" will show much improvement.

 

If a rarely used room is closed off and not ventilated and/or heated, then the surface temperature of the inner lining will always tend towards the temperature on the outside - insulation only reduces the rate of heat transfer, it doesn't guarantee a higher temperature inside the boat under all conditions.

 

Condensation will then occur whenever there is a slight increase followed by a decrease in temperature inside the boat (as may occur of a sunny day in winter, for example).

 

However improving the ventilation will make a huge difference because it will also ensure the circulated heat reaches all parts of the boat.

[Jrtm]

I know it may not help but before i put heating in the boat to keep it dry i get quite bad condensation in the engine room (metal) but none in the back cabin (all wood)

 

The only way to stop the condensation is to stop the metal getting so cold when its cold outside.