Ceiling Insulation renewal

[Jim Jones]

I am busy reworking the interior of my boat.

This is how far along I am....



The insulation in place is polystyrene - approx 25-30mm thick. Its been there many years. The plastic sheeting is telling because polystyrene absorbs water moisture - the plastic sheeting must be there as a vapor barrier for this reason.

Not related to boats, but I have been in a fish room (full of aquariums) that had its ceiling lined with polystyrene sheets and the stuff was falling out of the ceiling because of the weight of the water it had absorbed in that damp environment. Ok our boats are not likely to see that sort of moisture but the point is the stuff does absorb water pretty readily.

Ok so I need to replace it. But with what? A closed cell foam of some sort I would think - but what material? I would like to stick to 20mm thick if possible so that I can leave a small air gap between the insulation and the ceiling panels.

The boat is Aluminium. The roof of the coach house/saloon area is Aluminium. A good conductor of heat.

Any suggestions on what to use for this ?

[Jim Jones]

This is why I am replacing timber work in the galley/Saloon area - look at that rotted wood.




That bit of wood was up against the Perspex window - obviously leaking and for a good many years it seems.

I am replacing most of the wood work with Iroko or Sapele. At the moment I am thinking of going with Iroko.

The Port side Saloon area around the windows seems to have faired bettter




Interesting that the Insulation material is branded DOW.

[Scubaseas]

No idea what is available in your area. I'm in the States and would use urethane/polyisocyanurate sheet insulation which is closed cell foam. easily handled, cheap and fairly low fire rating. Not sure XPS extruded polystyrene absorbs water. It's rated for ground contact and exterior basement insulation as where urethane is not ground contact rated. They also use XPS under floor slabs. I'd use the urethane/polyiso just because it is slightly less flammable than XPS.

[Jim Jones]

Yeah its a bit of a mess actually.

Some of it is a DOW product, other sections are clearly a Polystyrene.

Definitely replacing it all with something a bit higher in performance.

A closed cell polyurethane ?

As far as I know, polyurethane has about the best performance out there but it needs thickness. I am wondering if there is anything else out there that may perform better then a polyurethane in thinner thicknesses ?

I do know that the sweet spot for insulating refrigerators and freezers is about 90mm of PU insulation - beyond that diminishing returns set in.

But I dont have 90mm to play with, hence looking for something else.

I fully expect to be importing whatever the best material is. Would be great if I could find it locally but my hopes are not high for that.

[Scubaseas]

Most everyone these days is making XPS or Polyisocyanurate. Dow made a Urethane that was 1" thick, vinyl coated and 1 hour fire rated. About $150/4'X8' sheet.

Some insulation is better than no insulation. Aerogel works the best for R value per inch but you may as well gold plate it as it's very expensive stuff.

[Jim Jones]

Aerogel. Hmmm, will look it up. Who needs two kidneys anyway....

[Jim Jones]

I wonder if vacuum panels might be a thing to fit here ?

Vacuum is the absolute best insulator known.

[Scubaseas]

Originally Posted by Jim Jones

I wonder if vacuum panels might be a thing to fit here ?

Vacuum is the absolute best insulator known.

As long as they hold the vacuum. Same price neighborhood as Aspen Aerogel Spaceloft.

Are you trying to keep the heat in or the hot out? If hot out putting up a boat shade will help a lot.

[Jim Jones]

Heat out - I am in a very hot area. Very hot. Avg ambient temp is around 35c year round but drops to around low 20's (Celsius) at night. Water temp is 26c year round.

I have another thread here about an awning over the saloon roof. I've been researching all afternoon looking for a ripstop canvas that has insulation attached to it - there are several available locally so will be checking them out.

Getting the insulation right will be important. I dont have enough battery to run air-con. I was going to put in a big battery bank but have scaled this down to ....I am hoping.... about 45 kWh. Worst case scenario I can fit in a 30 kWh battery bank. But that is not big enough to run all the needed loads and air-con.

Considering put a hatch in the Perspex window to get more airflow through the boat.

[Scubaseas]

My boat is in the Houston area. Summers are wicked hot like 38*C at times and 90% humidity. I use an open mesh sunsail to keep the deck from getting hot and it makes the interior about 8*C cooler. There is no way I could live on the boat without A/C as I had a senior Belgian Malinois/GSD mix dog that doesn't tolerate heat well. Shore power or a genset works fine for A/C. A huge battery bank will run A/C but how are you going to put the energy back into the house bank?

[Jim Jones]

Luckily I dont have to deal with humidity.

I will charge the bank from shore power before I leave my dock. Then once away from my dock I will have to rely on whatever shore power I can find as I go and i am intending to install a large case 48v 150w alternator. I have some solar but its not much. Currently about 400w at 12v - replacing all that with more up to date efficient panels but its still not that much.

This is why I cant even think about air-con - would be nice to have but I need my power for other things.

[Jim Jones]

In my research I came across this.....

"Although both expanded and extruded polystyrene have a closed-cell structure, they are permeable by water molecules and can not be considered a vapor barrier. There are interstitial gaps between the expanded closed-cell pellets in expanded polystyrene that form an open network of channels between the bonded pellets. If the water freezes into ice, it expands and can cause polystyrene pellets to break off from the foam."

I have found a supplier of Armaflex - so will most likely use that.

Other interesting materials ;

https://docs.rs-online.com/eadd/A700000008919850.pdf - Calcium-Magnesium Silicate Thermal Insulation

https://za.rs-online.com/web/p/therm...lation/8405526 - Flame Retardant Superwool 607 Fibre Thermal Insulating Sheet