weird condensation lines on ceiling

[chubby]

Hello

 

when i got up this morning there are strange lines of condensation at parallel intervals on the ceiling all the way down the cabin . Ive not seen this before but last night was colder than it has been lately.

 

Is this from the original construction ? It looks like gaps in the insulation . I m not too concerned as i expect this may be normal (ish) at this time of year and perhaps thru till Spring . It took 2 minutes to wipe it off so not a chore to sort it out but am i right to think this is only to be expected ?

[Mike Tee]

steel roof beams not insulated?

[chubby]

Thats what i suspect it to be . The lines of condensation are at such regular intervals that i suspect its exactly this . The boat was built in 2001 and if this has happened each winter then it seems to have done no damage to the wood so im not overly concerned but it was weird when i first saw it .

cheers

[Ex- Member]

The surface might well be fine but I would reckon that behind might be quite a mess and possibly rotting if it's condensating on any of the steel ribbing. The outside will fair ok as it will quickly get dried. Having said that if the backs of the lining were varnished then they could well hold up for years.

 

What is the boat insulated in BTW

 

Personally I would be far from happy with this occuring anywhere as it usually comes to pass there's a lot more to the problem than initially meets the eye.

[chubby]

Its sprayfoam insulated - but there seems to be not much of it to my inexperienced eye .... an inch or so?

 

Its only cropped up this morning and its the first time ive seen it . When i bought the boat i repainted the interior . The ceiling was painted white and i did a thorough job not just slapping paint on . It took me two weeks for the 50 ft or so of cabin space ( including the walls ) . At no point did i see any evidence of a problem with the surface . None of the panels look in anyway affected . The bathroom ceiling is unpainted ( i ran out of motivation !) and two lines are more prominent but again they just wipe clean . If it is a gap in insulatiion that would be strange as i thought speay foam just went all over the steel shell . Maybe theres just less foam ?

As i say im not concerned ... yet but i guess its better to be aware of potential probs down the line as im planning on holding onto this boat ling term If it did turn out that at some point in the future the panels needed replacing i guess id be able to make some changes then .

 

cheers

[Mike Tee]

First time it snows or is frosty you will see a mirror image outside on the roof where the beams transmit heat to the frost. Not a lot that can be done I would have thought, without taking the ceiling down. If, as has been mentioned, it was varnished on the non visible side, or maybe treated with preserver, you may get away without serious problems for a few years.

[blackrose]

steel roof beams not insulated?

 

Very few steel canal boats have properly insulated roof supports because they are just battened with wood which are either taped over so the sprayfoam does not stick to them, or the foam is cut back at these points. So it doesnt actually matter how thickly the foam was applied because most steel boats will have thermal bridges all the way across each roof support, as well as down the battens along the hull and cabin sides. Even if the hollow square section steel beams that some boats have are filled with foam to prevent condensation building up inside them, there will still be a thermal bridge around their perimeter. Its just poor insulation design Im afraid and the same thing is done by just about everyone who fits out a canal boat - amateur or professional.

 

Someone will probably say that the wooden battens are the insulation, but anyone who knows anything about the relative insulation properties of different building materials will know that wood is a pretty poor insulator.

Edited October 25, 2013 by blackrose

[Ex- Member]

 

Very few steel canal boats have properly insulated roof supports because they are just battened with wood which are either taped over so the sprayfoam does not stick to them, or the foam is cut back at these points. So it doesnt actually matter how thickly the foam was applied because most steel boats will have thermal bridges all the way across each roof support as well as the battens along the hull and cabin sides. Even if the hollow square section steel beams that some boats have are filled with foam to prevent condensation building up inside them, there will still be a thermal bridge around their perimeter. Its just poor insulation design Im afraid and the same thing is done by just about everyone who fits out a canal boat - amateur or professional.

 

Someone will probably say that the wooden battens are the insulation, but anyone who knows anything about the relative insulation properties of different building materials will know that wood is a pretty poor insulator.

 

An insulator never the less though

 

ETA

 

I just had a thought about this remembering how we battened out.

 

Just took a look at R values of building materials. It seems 3/4 plywood has an R value of 0.94

 

We battened the cabin sides in a double thickness 2 inch strips of ply glued together with Gorilla glue. So in total 1.5 inches of ply giving an R value of 1.86 and then of course lining thickness and Oak trim thickness on most of the battens.

 

Standard 1 inch solid wood though is 1.56 so wood batten is much better than ply inch for inch. So worth bearing in mind if anyone's about to batten out.

 

We've never had any sign of any kind of reaction through linings weather it from where battens are or anywhere else.

 

I would certainly consider condensation forming as the op describes as quite a problem which might prove to be even worse in colder weather.

Edited October 25, 2013 by Julynian

[blackrose]

 

An insulator never the less though

 

 

And also a conductor!

 

Many materials can be considered insulators, it just depends what youre comparing them to. Likewise many materials can be considered a conductors of heat.

 

The point is that ALL types of wood are much poorer insulators and much better conductors of heat than the sprayfoam, foam board or mineral wool used to insulate our boats. Wooden battens that connect warm internal linings to cold external steel therefore constitute thermal bridges - lots of them all over our boats. Theres really little point in a boat having 3 inch thick sprayfoam for example, when it also has so many conduction pathways for heat to escape. Like I said, from an insulation perspective its just bad design.

Edited October 26, 2013 by blackrose

[colin stone]

It is the battens. One way to minimise is to have battens for panelling run at right angles to the frame battens. Then there will only be thermal shorts at the intersections.

But loss of internal room.

I have the same issue but only in the very cold weather in spaces where there is more humidity - cabin and bathroom.

[Bee]

condensation only forms on the surface, I doubt there is anything much happening under the lining, if the lining is fixed to the steel with self tappers and the heads are exposed you will get drips, if there is a reasonable amount of covering you will not really have a problem, I would not worry unless it gets a lot worse. The bad places are dark unventilated corners, under beds, behind furniture etc.

[nb Innisfree]

Problem with thick insulation on the ceiling is reduced headroom, I took a chance and used self tapping screws to fix 9mm ply strips to our 1" square roof bars and covered those with 6mm ply, fortunately we have had no probs with condensation.

[Ex- Member]

 

And also a conductor!

 

Many materials can be considered insulators, it just depends what youre comparing them to. Likewise many materials can be considered a conductors of heat.

 

The point is that ALL types of wood are much poorer insulators and much better conductors of heat than the sprayfoam, foam board or mineral wool used to insulate our boats. Wooden battens that connect warm internal linings to cold external steel therefore constitute thermal bridges - lots of them all over our boats. Theres really little point in a boat having 3 inch thick sprayfoam for example, when it also has so many conduction pathways for heat to escape. Like I said, from an insulation perspective its just bad design.

 

That's why I quoted an R value to quantify. The amount of thermal bridges/pathways as a total percentage of all insulated areas is very small but of course significant. Spray foam at 3 inches adds very little insulation value anyway, but surely you're not suggesting that insulation is a waste of time if thermal bridging exists. I think out boat would be rather chilly without it.

 

Thermal bridging will cause heat loss at those points it exists, but will not drag down the performance where insulation is at a full even thickness. It should perform as it's designed to. There's also similar heat loss through portholes doorways & hatches, these though don't directly affect the way the insulation performs either.

 

As I've always said badly uneven and thinly applied spray foam insulation is a much bigger problem, I think yet again the OP mentioned discovering very thinly applied spray foam and of course it will be uneven as well I suspect. Large uneven air gaps behind panelling allow warm air plenty of opportunity to travel to the colder spots of "thin insulation" will undoubtedly cause much more heat loss than Thermal bridging.

 

"The problem was that the installer was doing his first spray foam job ever, and the thickness of the insulation varied from zero (visible roof deck) to about 9". Unfortunately, good average thickness doesn't cut it. The coverage needs to be uniform because a lot of heat will go through the under-insulated areas. (See my article on"

 

Interesting article on sprayfoam.

http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/25546/4-Pitfalls-of-Spray-Foam-Insulation

[Paul's Nulife4-2]

Hi gang,

I have exactly the same problem re the condensation lines on ceiling throughout my boat. What do you think about,drilling strategic 5mm holes or so, through ceiling,into box section ribs, then using cans of foam injected into the space ?. Would this help,or hinder ?.

[Ex- Member]

Hi gang,

I have exactly the same problem re the condensation lines on ceiling throughout my boat. What do you think about,drilling strategic 5mm holes or so, through ceiling,into box section ribs, then using cans of foam injected into the space ?. Would this help,or hinder ?.

 

I know a few people who have done this but in general where cavities were spray foam was thinly applied, filling the cavity worked pretty well, finding the actual steel ribbing would be tricky though and thermal bridging will still occur through the steel even if full of spray foam. It's not a proper solution but the alternative is very expensive if having to strip and insulate properly again from scratch.

 

Spray foam is definitely the best insulation, but unfortunately in my experience applied poorly and inadequately 90% of the time.

[Paul's Nulife4-2]

Yer,that makes sense I suppose,,I certainly ain't going to rip my ceilings down. I would like to try & solve the problem though. I can see exactly where my roof box sections are,

Would air flow help,more than the sprayfoam idea,maybe little vents,each side & or in the middle, or something like that. Or is it a case of live with it,do you think.

[Ex- Member]

Yer,that makes sense I suppose,,I certainly ain't going to rip my ceilings down. I would like to try & solve the problem though. I can see exactly where my roof box sections are,

Would air flow help,more than the sprayfoam idea,maybe little vents,each side & or in the middle, or something like that. Or is it a case of live with it,do you think.

 

Might be a case of living with it. You could try putting foam in a section of roof somewhere though as an experiment, maybe one of the smaller cabins and see what effect if any foaming has. It certainly shouldn't make anything worse so for me it would definitely be worth a try.

 

Do you know what your boat is battened out with BTW, and are there large cavities behind panelling in roof sections do you know.

[Paul's Nulife4-2]

Yes,its an Aluminum boat, with Aluminum box section tac welded to the roof & walls,

None of the boat is sprayfoamed,its just loose Celotex or similar,in a 40mm cavity.(I know,ridiculous for such a boat, its a Sea Otter make by the way)

Thanks for your input Julynain,very knowledgeable.

Edited October 26, 2013 by Paul's Nulife4-2