Noob with insulation enquiries

[Pauliebeans]

Hello all, first post so go easy (though some tolerance of mild jibing and teeth-sucking allowed). 

 

I've taken the plunge and just bought a rusty old 70ft trad to renovate and liveaboard, as usual my timing has been impeccable with lockdown making things that little more difficult. 

First amongst the long list of jobs to complete is to rip out and replace most of the bedroom. The boat had been abandoned for 2 yrs prior with a mushroom vent stolen so a fair amount of water has come in through the roof. Most of the wood panelling, floor, and battens were damp so have been removed.  The water trapped in the roof has been re-condensing on the internal steel causing rust and  minor pitting, treated this with Aquasteel and repainted. 

 

I'm looking at using this to insulate the roof https://www.screwfix.com/p/ybs-superquilt-multilayer-insulation-1-5-x-5m/80967#product_additional_details_container

Description for those who don't want to click link - 

Multi-layer reflective foil insulation for roofs, walls and floors. Made with aluminium for maximum thermal performance, the reflective properties keep the living space warm in winter and cool in summer with effective solar over-heating barrier. Lightweight and flexible. Fast and simple installation without any harmful fibres or particles.

• Thermal Resistance up to 2.50W/m²K
• Thickness: 40mm

 

Seems easy enough to fit and acts as a vapour barrier when sealed with aluminium tape, also gives a U-value of 0.4.   

Just wondering if anyone here has experience of the same? Does it provide enough insulation on its own (bearing in mind I'm a southern softy)? What adhesive is best to fix to the steel? Does it provide effective vapour barrier?

 

I'm aware foil bubblewrap is NOT the answer but this isn't bubblewrap. Would consider Kingspan/Celotex but concerned trying to fit to the curved roof would result in lots of snapped and ultimately useless insulation boards.

 

Previous installation was 25mm polystyrene which I'm trying to avoid for fire safety reasons

 

Theres some 40mm blue foam roof insulation to re-install under the gunwhales, planning on 25mm Kingspan for the walls. All sealed with foil bubblewrap and aluminium tape. 

 

 

Like I say, absolute newbie with only vague ideas of what I'm doing so any constructive advice most welcome... 

I'm sure I'll be back with more questions, probably a few tales of woe and if I'm lucky a few success stories too

 

 

 

 

[W+T]

Just do it right first time, sod the bubble wrap as its no cop, and use PIR foam, either spray on sheets.  all is to say, loads will come on yet with replies, and sit back and weep lol ha ha

[Ryeland]

25mm Celotex/Kingspan will bend quite well.

 

Richard

[TheBiscuits]

That's quite a claim at 2.5 R value for 40mm as a flexible blanket!

 

I'm not saying they are incorrect, but that is the equivalent of 50mm Kingspan Kooltherm or around 55mm Celotex  (not available at this size, you need to go lower 50mm - 2.25 - or higher 60mm - 2.70)

 

I would be interested to see how you get on with this.  It seems to be fancy rockwool inside two fancy foil blankets, so it would be a doddle to install compared to rigid sheets, and has the reflective properties of the foils. 

 

This probably means that in contact with a steel structure (the boat!) you need to downgrade the R-value, as the foil in contact will conduct heat it would be expected to reflect on one side, but it still sounds like it's easier to fit than Celotex PIR boards for similar insulation.

[Onewheeler]

48 minutes ago, Ryeland said:

25mm Celotex/Kingspan will bend quite well.

Two layers of 20 mm will bend even better!

[WotEver]

Loads of arguments for and against this particular snake oil.

 

A decent-looking experiment on this site...

http://multifoilexperiment.blogspot.com/2006/06/comparison-of-multifoil-insulation-vs.html

 

The data is quite conclusive - the multifoil insulation is not as good at retaining heat as the 50mm celotex although clearly it is better than no insulation at all. The repeat experiment for the multifoil insulation with a slightly different sealing approach gives almost exactly the same results. The foil behaves almost 50% worse than the celotex despite claims to the contrary.

 

However, bear in mind that all the foil manufacturers state that air gaps are needed between the foil and the object to be insulated.

[Man 'o Kent]

OK, bear with me here, I lined my steel workshop, (modified DIY build garage unit), with 50mm Celotex glued on with a no particular brand "no-nails" type glue. Five years later nothing has fallen down and there has been no evidence of condensation problems, the pre-painted steel sheet walls/roof are very thin material and exposed to all weathers and temperature extremes. Given that the assembly is liable to far more stresses, hot sun, thin material, expansion/contraction and has stood up to it I cannot but think that the thicker and therefore more stable construction of a narrowboat would lend itself to similar treatment.

 

I note that you envisage it as a liveaboard, in that case I think you should seriously consider a thicker material, say 50mm. While the loss of 100mm (4") of internal width might be thought a problem it can be mitigated by careful choice of facing trim.

[TheBiscuits]

20 minutes ago, WotEver said:

However, bear in mind that all the foil manufacturers state that air gaps are needed between the foil and the object to be insulated.

 

Cheers Tony.

 

That was exactly my gut response to it (see above!) but the numbers make it obvious it's not as good as it first sounds.

 

I would note though that celotex / kingspan are foiled products too, so probably have the same trouble in contact with steel!

 

I think that I will stick with my favoured insulation if there is a next time.  Foiled PIR foam boards (Celotex/Kingspan/whatever).

 

The way to do this it seems is as follows:

 

1. Stick boards to steel with very small blobs or stripes of PIR foam from a professional foam gum, not a DIY can-and-straw.  Curved deckheads (ceilings!) need to be dry fitted first using longitudinal cuts in the foam boards, then taken down and the cuts foamed before refitting or you get stripes of condensation!

 

This leaves a small airgap between the steel and the outer face of the insulation boards, which makes all the difference, but means you must:

 

2. Seal all gaps between boards using the same PIR foam gun, trim it back once set and foil tape over the joints, using foil insulation tape, not duct tape!

 

This technique is very very time consuming, so is only any cop for DIY on bare steel shells. 

 

All the pros use spray foam, because you allow a day for foaming and setting, a day for trimming back and you are installing the galley on day three.  The results are not as good 10 years later, but this is the only sensible commercial answer.

 

5 minutes ago, Man 'o Kent said:

50mm Celotex glued on with a no particular brand "no-nails" type glue. Five years later nothing has fallen down and there has been no evidence of condensation problems,

 

Crossposted, but yes, that's exactly what we are discussing.

 

The only reason I suggest PIR foam to stick the boards to the cabin is that it is slightly better at avoiding cold bridging, but you probably wouldn't notice the difference.

Edited April 30, 2020 by TheBiscuits

[Pauliebeans]

Wow!

Feel like I chose the right forum, thanks for your replies. Lots of useful info and avenues to consider there, I'm definitely feeling the benefit of your collective experience. I'll do some more research and shopping around based on those suggestions.

I hadn't noted the need for an air gap to achieve claimed efficiency so my 'too good to be true' suspicions seem confirmed.

 

One further thought... The rest of the interior is staying intact for now, but once the bedroom is completed I'll have one (hopefully) better insulated section of the boat in comparison to the rest. Should I anticipate any issues at the point where the 2 sections meet or am I over thinking things?

 

 

 

.

 

[David Mack]

1 hour ago, Pauliebeans said:

One further thought... The rest of the interior is staying intact for now, but once the bedroom is completed I'll have one (hopefully) better insulated section of the boat in comparison to the rest. Should I anticipate any issues at the point where the 2 sections meet or am I over thinking things?

 

Try to make sure that your new insulation in the bedroom butts up tightly to the existing insulation beyond, and if possible tape over the joint with alumnised tape. Otherwise damp air will be able to get to the inside of the steel shell where the moisture will condense, and you may get water dripping thrpough the lining, particularly at gunwale level, and rusting of the shell.

[Ex Brummie]

Whatever you choose to stick you insulation with matters not. Once you put your lining on, that will hold it up.

[Movin' on]

8 hours ago, Pauliebeans said:

Wow!

Feel like I chose the right forum, thanks for your replies. Lots of useful info and avenues to consider there, I'm definitely feeling the benefit of your collective experience. I'll do some more research and shopping around based on those suggestions.

I hadn't noted the need for an air gap to achieve claimed efficiency so my 'too good to be true' suspicions seem confirmed.

 

One further thought... The rest of the interior is staying intact for now, but once the bedroom is completed I'll have one (hopefully) better insulated section of the boat in comparison to the rest. Should I anticipate any issues at the point where the 2 sections meet or am I over thinking things?

 

 

 

.

 

With all insulated areas its the gaps and joins that will cause you problems (with condensation often dripping down the grain of bulkheads/openings) not the the insulation itself - that's why spray foam is the best but not always practical esp in partial refits 

Have fun - pictures of the boat always maintain forum members interest

J

[koukouvagia]

Another route is to use slab insulation.

 

https://www.canalworld.net/forums/index.php?/topic/63615-insulating-a-boat-to-prevent-condensation/

(see post #8)