Polystyrene insulation

[blackrose]

17 hours ago, Tony Brooks said:

I never said it was not combustible but that I am as opposed to any fibre type insulation as you are to expanded polystyrene. Over the lift of a boat I feel condensation is far more of a danger that fire ...

I don't think condensation is really "a danger" is it? 

[Tony Brooks]

Just now, blackrose said:

I don't think condensation is really "a danger" is it? 

Yes it it engenders mould spores or if it allows the hull to perforate.

[blackrose]

4 minutes ago, Tony Brooks said:

Yes it it engenders mould spores or if it allows the hull to perforate.

Ok 

Hardly "far more of a danger than fire" though...

The bottom line is that polystyrene insulation has been superseded by better, more thermally efficient forms of insulation. That doesn't mean polystyrene doesn't work anymore, it just means it doesn't work as well as the materials it's being replaced with.

Edited March 3, 2018 by blackrose

[Tony Brooks]

9 minutes ago, blackrose said:

Ok 

Hardly "far more of a danger than fire" though...

The bottom line is that polystyrene insulation has been superseded by better, more thermally efficient forms of insulation. That doesn't mean polystyrene doesn't work anymore, it just means it doesn't work as well as the materials it's being replaced with.

I agree but the original question was, as I understood it, about an existing boat with polystyrene insulation. I don't think its the horror others have made it out to be so said so.

How many boats catch fire? How many boats have needed hull repairs? That's one half of the "risk" equation that seems to be being ignored here. If I were building form new I would probably use a "Kingspan" type materials and spray foam for gaps because it seems spray foam can be a very shoddy job. but the original question was not about a new build.

[jam]

On 3/1/2018 at 10:48, Dr Bob said:

If I was re-insulating a boat now, I would look at rockwool or mineral fibres and stuff it into all nooks and crannies. (….thats a non expert view).

Aah the new asbestos, should be interesting in years to come.

What most of the replies seem to have avoided is ensuring cables have an adequate air gap. It is generally a big no no to install cables embedded in high density thermal insulation on the majority of electrical installations as the cables would have to be derated by as much as 50%. There is no excuse on boat designs  not to use conduit or preferably trunking.

[TheBiscuits]

Just to throw a spanner in the works:

PIR/PUR Foam insulation (sprayfoam) degrades thermally over about ten years.  Ten year old sprayfoam has very similar insulation properties to an equivalent thickness of polystyrene.

I will repeat that:

Ten year old sprayfoam has very similar insulation properties to an equivalent thickness of polystyrene.

Sprayfoam ( Also Celotex etc sheets) reduces in insulation properties as it slowly outgasses over a ten year period from new.  This is well known in the industry, and is factored into the U-value calculations over a 25 year timespan.

It should still be more fire retardant than polystyrene, but as others have said by the time your boat is burning hard enough for the insulation to catch fire you should be off it anyway!

I will not link to the studies on this, because only @Dr Bob and @rusty69 would care about "Thermal Properties of Polyurethane-Polyisocyanurate (PUR-PIR) Foams Modified with Tris(5-Hydroxypenthyl) Citrate" and they might get over-excited

 

 

[ditchcrawler]

30 minutes ago, jam said:

Aah the new asbestos, should be interesting in years to come.

What most of the replies seem to have avoided is ensuring cables have an adequate air gap. It is generally a big no no to install cables embedded in high density thermal insulation on the majority of electrical installations as the cables would have to be derated by as much as 50%. There is no excuse on boat designs  not to use conduit or preferably trunking.

I would suggest that most cables are already de-rated by 50% due to sizing for volt drop not current carrying capacity

[MtB]

54 minutes ago, ditchcrawler said:

I would suggest that most cables are already de-rated by 50% due to sizing for volt drop not current carrying capacity

 

Isn't that the same thing?

A well insulated cable needs to be bigger so the volt drop is smaller so the heat generated by the cable resistance is reduced, becasue the higher insulation prevents the heat being dissipated.

I hope that's all clear now 

Edited March 5, 2018 by Mike the Boilerman
Spellin

[MtB]

1 hour ago, TheBiscuits said:

I will not link to the studies on this, because only @Dr Bob and @rusty69 would care about "Thermal Properties of Polyurethane-Polyisocyanurate (PUR-PIR) Foams Modified with Tris(5-Hydroxypenthyl) Citrate" and they might get over-excited

 

Oh gwarn gwarn gwarn gwarn gwarn.

I'm mortified you think Mrs Doyle and I don't care about such things. We are fascinated to hear this about sprayfoam. Does it continue to degrade in perpetuity? What does 'outgassing' mean? Does its function as a vapour barrier break down too?

So many questions your assertion raises!

 

 

Edited March 5, 2018 by Mike the Boilerman

[dmr]

3 minutes ago, Mike the Boilerman said:

 

Isn't that the same thing?

A well insulated cable needs to be bigger so the volt frop is smaller so the heat generated by the cable resistance is reduced, becasue the higher insulation prevents the heat being dissipated.

I hope that's all clear 

Yes and No,  Yes, cables are de-rated to prevent over-heating when the cable is thermally insulated, but cables in boats are also de-rated to avoid volt drop due to the long lengths involved. What Brian is saying is that the de-rateing needed to minimise volt drops is so big that we don't get anywhere near to the point where we need to worry about the heating effects.

A hot cable will show an increase in resistance so for a given current flow will get hotter and its resistance increase more so even hotter (positive feedback) and will surely explode. (a beer if you spot the logical error before midnight)

...............Dave

[MtB]

8 minutes ago, dmr said:

(a beer if you spot the logical error before midnight)

 

You cheat, you posted at 13 mins past midnight!

The logical error is the resistance goes up as the cable gets hotter so the current goes down As the power dissipated is the product of voltage and current a state of equilibrium probably occurs before the Cable Explosive Point is reached.

 

 

Edited March 5, 2018 by Mike the Boilerman

[TheBiscuits]

3 minutes ago, Mike the Boilerman said:

 

Oh gwarn gwarn gwarn gwarn gwarn.

I'm mortified you think I don't care about such things. I'm fascinated to hear this about sprayfoam. Does it continue to degrade in perpetuity? What does 'outgassing' mean? Does its function as a vapour barrier break down too? So many questions your assertion raises!

Oh behave. You don't care about the chemistry!

No, it doesn't get any worse once it has lost the magic warm insulating gases from inside it - it just turns into inert foam.

It remains as impermeable as it was originally, but having seen quite a few monkey installations of it that doesn't count for much.

Actually it is quite interesting (well to me anyway!) because it means that you are actually much better off with well installed Celotex / Kingspan / Whatever Aldi had in last week in the longer term as they have the double foil layer outside the foam.

7 minutes ago, dmr said:

A hot cable will show an increase in resistance so for a given current flow will get hotter and its resistance increase more so even hotter (positive feedback) and will surely explode. (a beer if you spot the logical error before midnight)

I just had a lightbulb moment

 

[TheBiscuits]

13 minutes ago, Mike the Boilerman said:

What does 'outgassing' mean?

Oops missed a bit.  That's when the damn plumber forgets the Hawk White and just spits on the copper olive

 

[MtB]

Just now, TheBiscuits said:

Oops missed a bit.  That's when the damn plumber forgets the Hawk White and just spits on the copper olive

 

 

Ah yes, Hawkwhite. Wonderful stuff but stinks. Is the cause of that old saying "Old plumbers never die.... they just smell like it"

[TheBiscuits]

2 minutes ago, Mike the Boilerman said:

Ah yes, Hawkwhite. Wonderful stuff but stinks. Is the cause of that old saying "Old plumbers never die.... they just smell like it"

"Not suitable for potable water"

"Ahh fekkit, it's from the Thames anyway!"

[WotEver]

8 hours ago, ditchcrawler said:

I would suggest that most cables are already de-rated by a fair bit more than  50% due to sizing for volt drop not current carrying capacity

Fixed yer quote

I’d suggest that a decent installation sizes cables at least twice or maybe three times their current capacity in order to minimise voltage drop. Take the commonly used “divide by three” rule of thumb as an example: 18A load, use 6mm² cable. That’s rated for 34A buried in insulation or about 40A in free air. 

7 hours ago, dmr said:

A hot cable will show an increase in resistance so for a given current flow will get hotter and its resistance increase more so even hotter (positive feedback) and will surely explode.

Witness all the glowing boats on a nice starlit night

[Tony Brooks]

7 hours ago, dmr said:

A hot cable will show an increase in resistance so for a given current flow will get hotter and its resistance increase more so even hotter (positive feedback) and will surely explode. (a beer if you spot the logical error before midnight)

...............Dave

Are you sure? I thought only special alloys as used in light bulbs and heating elements had a positive temperature coefficient and copper cable had a negative coefficient. Mr Google agrees. This means the resistance would drop as the temperature increased but as the current flowing is limited by whatever is at the end of the circuit any result of cable temperature rise is likely to be less heat generated, not more. Still, not alot of help if the heat can't escape though.

[Up-Side-Down]

On 03/03/2018 at 07:59, Tony Brooks said:

The later Mike and help engender more condensation and damp within the living area.

When assessing risk I was taught to consider both the likelihood of an even and the severity of the effects of that event. The two events (burning insulation and the defects from condensation, especially if trapped in fibres next to the steel hull) are at opposite ends of both considerations. Fire - very unlikely, condensation - very likely. Fire - could be lethal, condensation - no short tern danger at all unless you have lung problems.

My conclusion, and others can come to a valid different conclusion, is that the risk associated with "self extinguishing" expanded polysyllable (that I have seen put themselves out) is all but negligible for the majority of boaters so I prefer it to fibre products that I have seen to have adsorbed and held quantities of water and that are not vapour tight.

When I fitted out my own boat I followed received wisdom and used the self-extinguishing polystyrene which, btw, is distinguishable from it's combustable brethren by a faint red line across the sheet. As a builder at the time (20 odd years ago) I was very familiar with polyisocynurate/polyurethane type products but knew how easily they succumb to combustion. Tempting, at something around twice the insulation value per inch of thickness when compared with polystyrene or Rockwool .......... but a temptation I resisted purely on safety grounds!

[dmr]

10 hours ago, Mike the Boilerman said:

 

You cheat, you posted at 13 mins past midnight!

The logical error is the resistance goes up as the cable gets hotter so the current goes down As the power dissipated is the product of voltage and current a state of equilibrium probably occurs before the Cable Explosive Point is reached.

 

 

Im drinking the cider, (Thatchers rather than Westons, you have converted me) so typing very slowly,it was before midnight when I started

 

3 hours ago, Tony Brooks said:

Are you sure? I thought only special alloys as used in light bulbs and heating elements had a positive temperature coefficient and copper cable had a negative coefficient. Mr Google agrees. This means the resistance would drop as the temperature increased but as the current flowing is limited by whatever is at the end of the circuit any result of cable temperature rise is likely to be less heat generated, not more. Still, not alot of help if the heat can't escape though.

Well I did say there was a logical error,just talking sh*te with mtb really.  I did say "for a given current" so was assuming a constant current rather than the correct constant voltage source, but then again the current will only fall slightly as the cable resistance is only a small part of the circuit resistance so maybe I am correct

off topic, but I was once told that some early carbon resistors had a negative temp. coefficient,  carbon is group 4 so in some cases can show some semi-conductor behaviour???

...............Dave

[Peter X]

You can of course build a whole boat out of celotex, as seen in this classic thread:

Maybe a polystyrene hull is possible too, I don't know? After all, those polystyrene cups hold coffee don't they?

[Machpoint005]

23 minutes ago, Peter X said:

Maybe a polystyrene hull is possible too, I don't know? After all, those polystyrene cups hold coffee don't they?

That would be interesting when meeting a tupperware boat around a blind bridge'ole, let alone a steel one!

[Neil Smith]

1 hour ago, Up-Side-Down said:

When I fitted out my own boat I followed received wisdom and used the self-extinguishing polystyrene which, btw, is distinguishable from it's combustable brethren by a faint red line across the sheet. As a builder at the time (20 odd years ago) I was very familiar with polyisocynurate/polyurethane type products but knew how easily they succumb to combustion. Tempting, at something around twice the insulation value per inch of thickness when compared with polystyrene or Rockwool .......... but a temptation I resisted purely on safety grounds!

I am also a builder just retired after 40 odd years in the trade, and we started using celotex/ kingspan when it first came out and yes it will burn if you get the fire hot enough but you cant light it with a match unlike polystyrene, even the self-extinguishing stuff will burn at lower temps than celotex as I proved when we had a burn up in my field of loads of old building materials.

Neil

[Dr Bob]

1 hour ago, Neil Smith said:

I am also a builder just retired after 40 odd years in the trade, and we started using celotex/ kingspan when it first came out and yes it will burn if you get the fire hot enough but you cant light it with a match unlike polystyrene, even the self-extinguishing stuff will burn at lower temps than celotex as I proved when we had a burn up in my field of loads of old building materials.

Neil

The both burn. The difference is PU foam is a thermoset and when it burns it stays put. PS foam on the otherhand is a plastic so it melts to a 'water like viscosity' and runs down an pools on  the floor and then burns. The heat is therefore more concentrated where the PS is flowing to, rather than spread out (or covered by wood) as the PU foam is likely to be. Any 'plastic' (ie not thermoset) should not be used for this type of application (viz grenfil tower - polyethylene) but I guess I would be happy in a boat as I will be out before the PS catches light.

[Up-Side-Down]

2 minutes ago, Dr Bob said:

The both burn. The difference is PU foam is a thermoset and when it burns it stays put. PS foam on the otherhand is a plastic so it melts to a 'water like viscosity' and runs down an pools on  the floor and then burns. The heat is therefore more concentrated where the PS is flowing to, rather than spread out (or covered by wood) as the PU foam is likely to be. Any 'plastic' (ie not thermoset) should not be used for this type of application (viz grenfil tower - polyethylene) but I guess I would be happy in a boat as I will be out before the PS catches light.

I thought Grenfil was Polyisocyanurate – No? Which I must admit has been bothering me as I've fixed a lot of the stuff in black and white timber frame buildings as a replacement for time-served wattle and daub.

[Dr Bob]

14 hours ago, TheBiscuits said:

Just to throw a spanner in the works:

PIR/PUR Foam insulation (sprayfoam) degrades thermally over about ten years.  Ten year old sprayfoam has very similar insulation properties to an equivalent thickness of polystyrene.

I will repeat that:

Ten year old sprayfoam has very similar insulation properties to an equivalent thickness of polystyrene.

Sprayfoam ( Also Celotex etc sheets) reduces in insulation properties as it slowly outgasses over a ten year period from new.  This is well known in the industry, and is factored into the U-value calculations over a 25 year timespan.

It should still be more fire retardant than polystyrene, but as others have said by the time your boat is burning hard enough for the insulation to catch fire you should be off it anyway!

I will not link to the studies on this, because only @Dr Bob and @rusty69 would care about "Thermal Properties of Polyurethane-Polyisocyanurate (PUR-PIR) Foams Modified with Tris(5-Hydroxypenthyl) Citrate" and they might get over-excited

 

 

Crackers Biscuits,

@rusty69 and I are very interested in these technical papers but I am not sure I would pay too much notice of this one. This paper is all about finding a cheaper polyol to use as one of their reactants for the Polyurethane-Polyisocyanurate (PUR-PIR) foams and almost exlcusively targets high temperature stability. Now, maybe high temp stability (viz above 300°C) means higher crosslink density, so a more dense close cell nature, so better longevity to insulation properties. I would urge all readers here to review said paper to convince themselves that other papers may be better. Paper here at.

https://www.omicsonline.org/open-access/thermal-properties-of-polyurethanepolyisocyanurate-purpir-foamsmodified-with-tris5hydroxypenthyl-citrate-2090-4568-1000148.php?aid=74306

There are a few things I would point to. Firstly this is all about a way to make cheaper polyols. They have only done it in a 3 necked 500ml flask (I would have use a 2 necked flask). There is zero scale up information. You cant comercialise something made in a 3 necked flask (or 2 necked for that case). You need significant scale up eperience which in turn requires a detailed risk assessment. If you are using 2-hydroxypropane-1.2.3-tricarboxylic acid as a reactant, you have to be careful. Secondly, the 2-hydroxypropane-1.2.3-tricarboxylic acid was supplied by Brenntag Poland LLC company in Kędzierzyn Koźle (storage in Toruń). With Brexit so close, I would think the import duty on said intermediate would seriously compromise the economics of scale up. All in all this is a typical university research project (when did university research projects ever create anything useful) and is on a hiding to nothing. Rusty, would you agree? Can you see any other serious issues in the paper?