Insulation

pmagowan

pmagowan

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I have been researching this subject as an offshoot from the Northwest passage thread and would be interested in opinions. Most of the information online is about spray foam insulation on steel boats. My boats construction will be cold moulded wood and glass reinforced epoxy composite. So, on both the outside and inside of what will essentially be a wood core there will be glass reinforced epoxy. Since I am thinking this boat may be used in cold climates (colder even than ours) then insulation becomes a concern.

Big questions are;

What type of insulation?
Do you insulate under the waterline?
Windows, double glazed glass or plastic, thermally efficient frames?
Ventilation, is there any way to be heat efficient?
Water and fuel, do their tanks need insulated (mine will be integral to the structure)?

Also, heating would be of interest. I am already keen on a integrated system between an Ebby and the engine to provide hot water and hot air but I am wondering if a diesel or solid fuel stove would be wise as a backup or simply a nuisance.

I would be interested in your views and particularly in the pros and cons of covering up the inside of a cold moulded boat with insulation and thus hampering any visual clues to a failure of the epoxy layer.

Thanks
 
Water (moisture in the air) will condense when it hits a cold, impermeable barrier. In the case of a boat, that is the hull, windows, etc. insulation needs to be laid in direct contact with these surfaces. If you leave a void (akin to a cavity in a house) it will get damp.

Spray on closed cell polyurethane is probably the way to go, or if you have big areas of flat hull you could line that with precut boards of polyurethane. Glue them on using low-expansion foam, and don't leave any gaps behind. Other types of insulation (e.g. Polystyrene) will need to be thicker to achieve the same insulation level.

On ventilation, consider fitting a small MVHR unit. They can consume as little as 2w on trickle. These units act like a ventilation fan but contain a heat exchanger, so the air extracted from the cabin passes its heat across to the incoming, fresh air. They can be in the region of 80% efficient.
 
Kelpie said:
Water (moisture in the air) will condense when it hits a cold, impermeable barrier. In the case of a boat, that is the hull, windows, etc. insulation needs to be laid in direct contact with these surfaces. If you leave a void (akin to a cavity in a house) it will get damp.

Spray on closed cell polyurethane is probably the way to go, or if you have big areas of flat hull you could line that with precut boards of polyurethane. Glue them on using low-expansion foam, and don't leave any gaps behind. Other types of insulation (e.g. Polystyrene) will need to be thicker to achieve the same insulation level.

On ventilation, consider fitting a small MVHR unit. They can consume as little as 2w on trickle. These units act like a ventilation fan but contain a heat exchanger, so the air extracted from the cabin passes its heat across to the incoming, fresh air. They can be in the region of 80% efficient.
Click to expand...

Thanks, my concern with spray on foam is that it sticks like the proverbial and it also is difficult to get a good finish. I worry that any work to the hull would be impaired by the insulation. Also, I suppose it would need to be a closed-cell foam to prevent getting wet. I have never heard of a MVHR being used in anything other than domestic construction but they are relatively simple devices so I see no reason why not. I wonder, since I am going to have blown air, whether I could design a whole boat MVHR system. That would be more efficient than a couple of the bathroom types and might help the Ebby get started in cold conditions.

Has anyone used armaflex insulation? It seems to come in flexible rolls that you can stick on and is resistant to water and fire. Also, in house construction you would use a vapour barrier to prevent moisture being able to pass through the insulation material and reach the cold side where it would condense. I am not sure about the logistics of this on a boat. One good thing about the cold moulded method of construction is that their is relatively little in the way of internal ribs or frames to get in the way. It is more or less a monocoque construction. The only frames that need to be permanent are those that will form the internal bulkheads.

I will now be researching MVHR's which I have already done for domestic property but not for a boat.
 
pmagowan said:
Thanks, my concern with spray on foam is that it sticks like the proverbial and it also is difficult to get a good finish. I worry that any work to the hull would be impaired by the insulation. Also, I suppose it would need to be a closed-cell foam to prevent getting wet. I have never heard of a MVHR being used in anything other than domestic construction but they are relatively simple devices so I see no reason why not. I wonder, since I am going to have blown air, whether I could design a whole boat MVHR system. That would be more efficient than a couple of the bathroom types and might help the Ebby get started in cold conditions.

Has anyone used armaflex insulation? It seems to come in flexible rolls that you can stick on and is resistant to water and fire. Also, in house construction you would use a vapour barrier to prevent moisture being able to pass through the insulation material and reach the cold side where it would condense. I am not sure about the logistics of this on a boat. One good thing about the cold moulded method of construction is that their is relatively little in the way of internal ribs or frames to get in the way. It is more or less a monocoque construction. The only frames that need to be permanent are those that will form the internal bulkheads.

I will now be researching MVHR's which I have already done for domestic property but not for a boat.
Click to expand...

Though not remotely in "cold climates", I watched a guy in a big cruising cat line his boat with the 2 pack sprayed foam insualtion. It took him some time to get the spray method right- for the thickness he wanted, but the end result looked excellent and he said it had transformed his boat.
He hired the equipment and bought as much foam compound as he required (more than). Requires serious PPE as the vapours are pretty toxic. I considered it, but went for self adhesive 6mm claose cell foam, on a roll. Fairly easy to fit and no worries about poisoning myself, though I was confined to early summer installation to have the surfaces both clean and dry beforehand.
 
pagoda said:
Though not remotely in "cold climates", I watched a guy in a big cruising cat line his boat with the 2 pack sprayed foam insualtion. It took him some time to get the spray method right- for the thickness he wanted, but the end result looked excellent and he said it had transformed his boat.
He hired the equipment and bought as much foam compound as he required (more than). Requires serious PPE as the vapours are pretty toxic.
Click to expand...

I helped a mate and his dad with building a medium-sized steel industrial unit (6-car workshop plus small spray-bay for parts). They got it spray-foam lined by a guy with the foam supply kit built into a van, which he parked outside and ran long hoses in to where he was working. Mate's dad had tried it himself before and said it was quite hard to get an even thickness and smooth finish, hence the pro who did a far better job in much less time.

I think that's definitely the way to go on a steel boat, with a good epoxy paint system first, but I'm not sure about a wood-epoxy hull. Most don't seem to line them as such at all.

Pete
 
Yes, insulation seems to be a bit of an afterthought in most boats and perhaps this is simply because we only tend to use them in good weather.

I have been looking at the MVHR idea and it is starting to get the cogs turning. Essentially an MVHR system acts as a large dehumidifier which could be very useful on a boat. It uses only the energy needed to run a small fan. Since I am already running ducting in for the forced air heating then it really should not be too hard to run in some extraction vents too. They could be directed over sleeping areas, the galley, wet locker and in the heads compartment. This would allow me to extract the air in a controlled fashion dependent on things like internal humidity and temperature and even if there were fumes or gas. It would mean going without passive ventilation or, at least, having the passive ventilation so that it can be shut down. Solar could power the fan without any trouble. The heat of the internal air would be recovered by running it in parallel with the incoming air through a large area heat exchanger. I might even be able to build my own. The Ebby forced air heater could be fitted in series so as to use the same ducting. It sounds like it could be a very good system, if slightly more complicated than a standard dorade vent.

Insulation wise I am veering towards the closed cell foam as I think it could be added and removed in a much more controlled fashion. I know the spray on stuff is very good but it does also seem very permanent and messy. Thanks all for your thoughts. Any ideas on insulating under the waterline, bilges et al? Should the insulation maybe follow the bottom of the cabin sole so that the living spaces are enclosed but the bilges are free?
 
I wonder whether you could make your own small MVHR unit, based perhaps on a tumble dryer heat exchanger? Small computer fans could provide quiet air movement.
 
pmagowan said:
Since I am already running ducting in for the forced air heating then it really should not be too hard to run in some extraction vents too. They could be directed over sleeping areas, the galley, wet locker and in the heads compartment.
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Certainly on larger vessels it's completely standard to have mechanical extraction. Not sure they bother with heat exchange when they have loads of spare energy to use for heating, but on a yacht if you can arrange it then why not.

On Stavros more or less all the extracts were in the various heads spaces, which had small gaps under the doors to allow the air in. The air would flow in through the sleeping cabins and out through the heads, taking any smells with it.

Pete
 
pvb said:
I wonder whether you could make your own small MVHR unit, based perhaps on a tumble dryer heat exchanger? Small computer fans could provide quiet air movement.
Click to expand...

Sounds good to me. The small heat-exchange extractor unit in my bathroom is far from sophisticated, just a few thin layers of plastic crimped together. But it blows in a gentle stream of fresh air which is not noticeably cold even on frosty days. The stainless heat exchanger in my condenser tumble-drier looks far more convincing, loads of surface area with thin fins and convolutions.

Pete
 
I have been designing an MVHR in my head since the idea came up. I think it should be pretty straight forward and could use copper wires as a heat exchange medium. The air extract would blow out through a tube containing a matrix of fine copper wires that project out into a surrounding tube which has the cold air coming in. The heat would travel along the wires and heat the incoming air. The key is the graduation so the hottest wires would be the ones the hot extract air hits first and the cold incoming air hits last. That way the by the time the extract air leaves it should be almost as cold as the external air and vice versa.

I am now trying to think of a way to make the matix as I would want to get it very efficient. I could easily add the Ebby in downstream so that it is only heating pre-warmed air. A computer fan, or perhaps a slightly better electrically sealed fan, could do the blowing in standard mode and the Ebby would take over if trying to heat things up.
 
pmagowan said:
Yes, I have looked at the ones designed mostly for bathrooms but they are not as efficient as I would like and also I suspect they would not be up to the rigors of marine use.
Click to expand...

Agree, the one linked above looks plasticky and production-engineered to me. I'd fit it in a house as-is, but I wouldn't choose it as a base to convert into a boat version.

Pete
 
There are some fabric systems comprising sponge & metalised films that are as little as 20 mm thick ( can be compressed at batten points etc)that are the equivalent to 250mm of glass wool.
There is one that is stitched & has a name like TSR10 ( forget correct name) it is not overly expensive but could be fitted behind headliners & hull liners cupboards etc & around bunk sides etc behind thin ply panels this would be removable. I have specified it on a number of building projects in the past & more manufacturers are coming up with similar products
The advantage over foam is that it is easy to install in voids & is relatively cheap & can be removed easily
Not sure about performance once wet & whether it would retain moisture & start to smell. I have specified it against damp walls Ok. But it should be Ok behind head linings & above waterline
In any event an insulation such as foam in the bilges could be a problem if constantly wet & the moisture may well start to smell
 
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