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TheSaintlyOne

Rockwood or 25mm Kingspan

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Hi I'm just about to take ownership of a Narrowboat Project. The boat has a marine ply coated fibreglass cabin top over a steel frame. The first job I plan to tackle will be applying some form of insulation to the interior which is in essence similar to a bare bones Sailaway. Just wondering what is the best insulation between Rockwool and 25mm Kingspan sheets. Both are fairly straightforward to fit and reasonably cost effective but which performs better. 

I plan to put the green MDF water resistant t&G effect panels over the top which will be painted above the Gunnels

And probably something like 12mm external grade ply below the Gunnels..

 

TIA

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15 minutes ago, TheSaintlyOne said:

Hi I'm just about to take ownership of a Narrowboat Project. The boat has a marine ply coated fibreglass cabin top over a steel frame. The first job I plan to tackle will be applying some form of insulation to the interior which is in essence similar to a bare bones Sailaway. Just wondering what is the best insulation between Rockwool and 25mm Kingspan sheets. Both are fairly straightforward to fit and reasonably cost effective but which performs better. 

I plan to put the green MDF water resistant t&G effect panels over the top which will be painted above the Gunnels

And probably something like 12mm external grade ply below the Gunnels..

 

TIA

 

Before doing anything to the 'cabin' strip it off completely and weld a 6" up-stand to the gunwale, THEN start to rebuild the cabin, overlapping the up-stand. It will never be watertight but that gives you the best chance of minimising the leakage.

 

The differing thermal expansion between the steel and the GRP / Wood mean that whatever you use to seal the joint will always break up.

 

If it is not too late - turn and walk quickly away from the project keeping your money (and hands) in your pockets

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Oh god it's not one of those sites its it!!!! I don't need advice on whether I should buy thanks done enough boat projects in my life to know the good from the bad so please stick to the question. I have no intention of removing the cabin top it was done professionally so I am not worried about it. Maybe I didn't explain the build properly but I know it's good 

13 minutes ago, ditchcrawler said:

The only thing I can say against the MDF idea is that its not good for fixing to 

Thanks for the advice would you reccomend anything else 😎

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7 minutes ago, TheSaintlyOne said:

Oh god it's not one of those sites its it!!!! I don't need advice on whether I should buy thanks done enough boat projects in my life to know the good from the bad so please stick to the question. I have no intention of removing the cabin top it was done professionally so I am not worried about it. Maybe I didn't explain the build properly but I know it's good 

Thanks for the advice would you reccomend anything else 😎

Ok - just trying to save you grief (and money), I assumed that as you didn't know the types of material to use (Kingspan, Rockwool, MDF) that you had little experience in boat fitting-out.

 

It doesn't matter how 'professionally' the GRP is joined to the steel - IT WILL LEAK.

Edited by Alan de Enfield

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1 minute ago, TheSaintlyOne said:

Oh god it's not one of those sites its it!!!! I don't need advice on whether I should buy thanks done enough boat projects in my life to know the good from the bad so please stick to the question. I have no intention of removing the cabin top it was done professionally so I am not worried about it. Maybe I didn't explain the build properly but I know it's good 

Folks on here want to be concerned and helpful - because the care.

Better it is to say - there are some challenges which you 'might have overlooked' - You're at liberty to ignore the comments, after all they are well meant

But

Don't shoot the messenger!

 

Alan-from-Enfield was only trying to point out that fibreglass cabins have been a problem from 'day one'. His suggestion might well save you some further grief later on...

 

I see he has replied. The numbers who have come on here and other fora send the same message.

OTOH if you manage to find a complete and permanent solution, do feel free to come back and enlighten the then assembled masses.

Some of the early fibreglass cabined boats looked wonderful and it would be greal to see at least one preserved.

 

 

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Look I'm sorry but the minute someone mentions project on any boat forums you get people come along and start telling you to walk away.

Fibreglass can only leak where there are holes thats why they make millions of boats out of it. So if a cabin top is done properly the possibillity of leakage is absolute zero!!!! The bigger issues im asking abot are condensation and warmth. Ive used kingspan and rockwool before but wanted to know other peoles ideas

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1 minute ago, OldGoat said:

Folks on here want to be concerned and helpful - because the care.

Better it is to say - there are some challenges which you 'might have overlooked' - You're at liberty to ignore the comments, after all they are well meant

But

Don't shoot the messenger!

 

Alan-from-Enfield was only trying to point out that fibreglass cabins have been a problem from 'day one'. His suggestion might well save you some further grief later on...

 

I see he has replied. The numbers who have come on here and other fora send the same message.

OTOH if you manage to find a complete and permanent solution, do feel free to come back and enlighten the then assembled masses.

Some of the early fibreglass cabined boats looked wonderful and it would be greal to see at least one preserved.

 

 

How can a fibreglass cabin top if constructed properly leak!!! Fibreglass doesnt leak...........!!!!

I would suggest the issue would either be poor construction or a mistaken case of condensation?????

 

But my issue as said is that on any boat forum the minute someone mentions buying a project boat people tell you to run which. And it was that sentence I reacted to not the talk of leakage 

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2 minutes ago, TheSaintlyOne said:

How can a fibreglass cabin top if constructed properly leak!!! Fibreglass doesnt leak...........!!!!

Nobody is saying that fibreglass cabin tops leak. What they are saying is that the joint between a fibreglass cabin top and a steel hull will leak (due to the different thermal expansion breaking any sealant used in the joint).

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Oki right I understand. So does this mean everyone who owns a fibreglass top boat should immediately sell up and walk away. I came here looking for helpful advice not to be told to walk away from a purchase!!! So sorry I've got frustrated but the final bit of "advice" was not nedded its an oppinion. And best left to threads where someone asks should I buy this boat or that boat

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30 minutes ago, TheSaintlyOne said:

Oki right I understand. So does this mean everyone who owns a fibreglass top boat should immediately sell up and walk away. I came here looking for helpful advice not to be told to walk away from a purchase!!! So sorry I've got frustrated but the final bit of "advice" was not nedded its an oppinion. And best left to threads where someone asks should I buy this boat or that boat

Kingspan is vastly better than rock wool in a number of ways: much better insulation for a given thickness, doesn’t absorb water. Downside is that in order to avoid condensation you need to have it in intimate contact with the cabin sides/roof. If there is air between the kingspan and the skin, you will get condensation. Kingspan is difficult to attach properly over curved surfaces. Which is why modern boats are spray foamed. Same stuff, but intrinsically in good contact with the skin, no air gaps. You could get a man in to spray foam it, it would be massively less work. If you must use kingspan, make sure it is in contact with the skin and seal the joints with expanding foam and tape.

 

Normal Kingspan and spray foam are polyurethane. There is a better type of foam - phenolic, which has better insulation for a given thickness. Kingspan kooltherm is phenolic, I think.

 

As to the comments on the structure of your boat, bear in mind that people are just trying to be helpful. Steel boats with wooden or grp sides/roof were built for a while in the 70s. They were always problematic at the point where steel meets wood or grp, due to the different thermal expansion coefficients. The point being to avoid spending a lot of time and effort making a lovely interior, only to have it spoilt by water leaks in year 2. As has been mentioned, if there is a steel upstand around the boat so that the grp overlaps, this goes a long way to curing the leakage problem. If there is no up stand, it will leak once there have been a few hot/cold cycles, and so best to fix this problem before you spend time doing the interior.

Edited by nicknorman

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Have you had a look at thermal foil insulation? Could be comparable to 25mm Celotex-type sheets. If you've got irregular surfaces/spaces, might be easier to fit. Note: air gap needed.

Edited by Sir Percy

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1 minute ago, Sir Percy said:

Have you had a look at thermal foil insulation? Could be comparable to 25mm Celotex-type sheets. If you've got irregular surfaces/spaces, might be easier to fit. Note: air gap needed.

I’m sure I read somewhere recently that thermal foil insulation was a con.

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1 minute ago, nicknorman said:

I’m sure I read somewhere recently that thermal foil insulation was a con.

Really? Was going to be installing soon. Haven't bought any yet. Can you remember where you saw that?

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This summer we did a quickie refit to prolong the life of one of my own boats until I have the time/resources to cut most of the cabin off (windows in the wrong places, tubular handrails etc) and do it properly. It's a boat with a complicated history, but the cabin is mid-80s and only insulated with 25mm polystyrene all over.

 

I decided we'd leave 25mm polystyrene, but add 3mm foil faced bubble wrap either side of it just as an experiment. In the end we'd only got room for one layer of the bubblewrap.

 

The 3mm foil faced bubblewrap claims to be equivalent to 55mm of polystyrene, and based on the negligible amount of heat we are putting into the boat so far this autumn I'm quite prepared to believe it.

 

Both my boats have Squirrel 1410s fitted, and this one is using about half as much coal - as in there's only just enough on the grate (with coal savers) to keep it lit - and the kids keep opening the windows because they're too warm.

 

It seems too good to be true (the cost for a roll big enough to do the whole cabin was about £70 from Screwfix), but I haven't found a downside yet.

Edited by Rose Narrowboats
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Just now, Sir Percy said:

Really? Was going to be installing soon. Haven't bought any yet. Can you remember where you saw that?

Had a quick look, but no.
If you think about it, the foil helps to reduce radiated losses. Only works (as you say) if there is an air gap between the foil and the next thing. But most of the losses are conductive, and for that you need thickness of something. Air is a good insulator but only if each air “compartment” can’t support convection. Ie you need very small compartments of air. Ie foam, not jumped up bubble wrap.

 

I put some thermal foil insulation around our calorifier, didn’t make much difference. I certainly would use it to insulate a boat. Sorry!

2 minutes ago, Rose Narrowboats said:

This summer we did a quickie refit to prolong the life of one of my own boats until I have the time/resources to cut most of the cabin off (windows in the wrong places, tubular handrails etc) and do it properly. It's a boat with a complicated history, but the cabin is mid-80s and only insulated with 25mm polystyrene all over.

 

I decided we'd leave 25mm polystyrene, but add 3mm foil faced bubble wrap either side of it just as an experiment. In the end we'd only got room for one layer of the bubblewrap.

 

The 3mm foil faced bubblewrap claims to be equivalent to 55mm of polystyrene, and based on the negligible amount of heat we are putting into the boat so far this autumn I'm quite prepared to believe it.

 

Both my boats have Squirrel 1410s fitted, and this one is using about half as much coal - as in there's only just enough on the grate (with coal savers) to keep it lit - and the kids keep opening the windows because they're too warm.

 

It seems too good to be true (the cost for a roll big enough to do the whole cabin was about £70 from Screwfix), but I haven't found a downside yet.

Yes it is too good to be true.

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4 minutes ago, nicknorman said:

...Air is a good insulator but only if each air “compartment” can’t support convection....

I would have been using it under the floor. Wouldn't be expecting convection to be a factor there. It would be good for that, do you think?

Edited by Sir Percy

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6 minutes ago, Sir Percy said:

I would have been using it under the floor. Wouldn't be expecting convection to be a factor there. It would be good for that, do you think?

As the link I posted earlier explains, if you put the foil bubble wrap in close contact with surfaces, it doesn’t work as in fact it’s a pretty good conductor. This is why you shouldn’t use it on cabin sides between outer and inner skin - which is what I presumed you were planning. For under floor, I guess it would work better because there is an air gap below it.

10 minutes ago, Rose Narrowboats said:

Yet based on the evidence in front of me, it works.

Unless there is an air gap between the foil and the next layer, you’re kidding yourself! But maybe there is?

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All permeable insulation needs a vapour barrier on the warm side. This is to stop warm moist air reaching the cold side of the insulation, where the moisture from the air will condense and cause dampness.

This applies to rockwool/glass fibre wool, & also to the joints in foam boards like Celotex & Kingspan.

The advantage of the boards is that the air can only get through at joints, so sealing those is sufficient. Fibre based insulation needs a vapour barrier on the inside over it's whole surface, and again the joints in that must be sealed totally. This is because Rockwool etc are not airtight, so the warm damp air from the boat interior gets inside the fibres and condensation forms in there.

Joints in insulation board can be sealed with waterproof tape or by spraying builder's foam into the gaps.

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4 minutes ago, nicknorman said:

 

Unless there is an air gap between the foil and the next layer, you’re kidding yourself! But maybe there is?

Steel shell, 25mm polystyrene, then the 3mm foil/bubblewrap/foil then the timber lining.

 

 

Edited by Rose Narrowboats

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Just now, Rose Narrowboats said:

Steel shell, 25mm polystyrene, then the 3mm foil/bubblewrap/foil then the lining.

 

 

In that case (no air gap) the foil bubble wrap is not contributing anything significant. How could it be?

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19 minutes ago, nicknorman said:

In that case (no air gap) the foil bubble wrap is not contributing anything significant. How could it be?

Probably because even the article you quoted accepts it has an R value of 1 when in direct contact. Other reasonable sources quote 1.1, the UK manufacturer (YBS Airtec) claims 1.497.

 

25mm Polystyrene has R value of between 0.6 and 0.7, so that extra 3mm of insulation has almost trebled the total insulation value.

 

Kingspan has an R value of 1.1 - but it seems it is generally accepted that it degrades with age and is equivalent to polystyrene after 10 years.

 

Sprayfoam has an R value of 1.2(ish) which is fine and dandy until you want to get at a rivet or do a welding repair.

 

 

Edited by Rose Narrowboats
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11 minutes ago, nicknorman said:

As the link I posted earlier explains, if you put the foil bubble wrap in close contact with surfaces, it doesn’t work as in fact it’s a pretty good conductor. This is why you shouldn’t use it on cabin sides between outer and inner skin - which is what I presumed you were planning. For under floor, I guess it would work better because there is an air gap below it.

Unless there is an air gap between the foil and the next layer, you’re kidding yourself! But maybe there is?

There's two key words in the article linked to: 'scam' and 'understanding'.

 

I don't think it's a scam if you understand how it works, and therefore how it should be installed for best results - so I was careful to make a note about the air gap required in my first post. 

 

For my particular application, the flooring will sit on 2x4" bearers at a level off the ballast (50mm tall, sitting on old cable). The foil should go on top of the ballast leaving ~one-and-a-half inch gap.

 

Also careful to use the word 'foil' rather than 'bubble-wrap'. If you've used some bubble-wrap to lag your calorifier, the bubbles would have been the only thing providing some benefit.

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