Insulation for boats: materials and methods

TwoHooter

TwoHooter

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I apologise if this has already been covered elsewhere on the forums - I have spent an hour searching and I can't find what I am looking for.

I am writing the specification for a new motor vessel which will be used for extended cruising by me and my wife. We expect to be living aboard for months at a time. We have to build our own boat because nothing on the market new or secondhand ticks all our boxes. Just to be clear about this, I am not going to try and design the boat. My role is to write a specification and pass that to a designer who will prepare the drawings. I have done this sort of thing before in other fields.

One of the reasons for building our own boat is that it has to be capable of being a home in all European climates including cold and damp (English winter) and baking hot (Greek summer), therefore it needs to be very well insulated. Ventilation and de-humidification are also important, but if the insulation is wrong we will be fighting a losing battle from the outset. I am amazed at just how badly insulated many modern boats are, including boats costing hundreds of thousands of pounds - it is one of the reasons why we are self-building.

My only experience of insulation concerns buildings. I don't know anything about how boats are insulated. Three things I really do want to know:
1. Are conventional calculations used on boats - specifically the U-value that is used for buildings in the UK? I would like to specify U-values for the different areas of the boat - will this be understood by a boat designer?
2. The length, beam and air-draught of the boat are limited by some of the places we want to take her, so the thickness of the external envelope of the living accommodation is important. It would be tempting to specify one of the modern thin insulation materials but I was badly bitten by an architect who specified a very thin insulation fabric for a house extension we built 7 years ago. The insulation sits under the pitched roof covering and there is no insulation in the loft. I thought it was a daft idea from the beginning but he talked me into accepting it and it passed Building Regulation approval OK. It is a total disaster - the extension is freezing - and we are now going to insulate the loft the traditional way with 150mm of fibreglass and provide loft ventilation. I am expecting to have to make the external envelope of the boat's living accommodation at least 60mm thick and possibly 110mm but I am just guessing. Does anyone have any experience of what actually works?
3. Windows, doors and hatches will of course have to be double-glazed. Does anyone have any experience of marine double glazing suppliers? The only ones I have found so far are http://www.trendmarine.com/glass-technology/insulated/ and possibly http://www.semarinewindows.co.uk

Thanks for reading.
 
I have to say that designing and building one's own boat simply to have better insulation seems like overkill. There are thousands of boats cruising Greek and UK waters in reasonable comfort. Perhaps you could look at modern motorhomes and caravans for some guidance? My motorhome is fully winterised, relying on foamed polyethylene about 40 - 50 mm thick in roof, walls and floor.
 
vyv_cox - Thanks for replying, I've seen your website and had already bookmarked you for some other advice I will be needing later!

The insulation is not the only reason for building our own boat. We have 12 items on our must-have list and after looking at a great many second hand and new (including brand new) designs we haven't found any that meet all our requirements. I know that all boats are a compromise but it seems daft to spend hundreds of thousands of pounds on something that only ticks 7 or maybe 8 of our boxes. Our requirements aren't absurd or outlandish. In fact all 12 of them are plain common-sense.

And when it comes to insulation have you looked at any modern motor boats with this in mind? Many of the boatbuilders don't even mention it in their specs! Why not? It's because there isn't any meaningful attempt to insulate the things. They just stick a diesel-powered hot-air heating system in and assume that's the job done. In what other field of design in the twenty-first century are thermal and noise insulation treated as unimportant questions? At this year's Southampton Boat Show I was asking about U-values and not one salesman knew what I was talking about! Admittedly I wasn't looking at the superyachts, but even so....

Anyway, I admit I have been hoping that 50mm of foam plus another 10mm for inner and outer skins will be enough, giving a total envelope thickness of 60mm, so perhaps I ought to look at motorhome manufacturers for confirmation. I wonder if they understand U-values?

EDIT: It's unfair to single out a particular boatbuilder, but just as one example, here's a specification for a mid-sized luxury yacht: http://www.outerreefyachts.com/photos/yachtDocs/551.pdf It mentions acoustic insulation for the engine room but that's it. No mention of thermal insulation or double glazing. Lots of energy-hungry kit like aircon and heating but insulation? Fergeddit. And we're living in 2014, not 1964!
 
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One thing is certain, you'll need spray on foam on the ceilings. I built my own boat and pushed poly sheets up between the frames, and in the winter the condensation drips down when too gets cold. Even the tinyest air gap between the insulation and the hull will cause problems; so it is totally impossible to get an airtight seal without spray on foam.
The vertical services can be insulated with any domestic product you fancy; I used foil covered bubble wrap and I'm not impressed with the result, so I'd stick with either thick poly sheeting or Rock wool with a vapour barrier.

remember that every morning a layer of mist forms just above the water, which causes damp air to be drawn into your boat. In my experience ventilation will not cure this, so you're going to need a dehumidifier of some sort.

ps: what sort of boat are you going to build?
 
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rustybarge - Thanks for your reply. I agree with what you say. Your point about interstitial condensation is very relevant. The accommodation will have effective insulation and vapour barriers on all 6 surfaces. I just don't yet know how best to achieve that.

Concerning de-humidification I think the best approach is to use an integrated HVAC system so that the humidity in the boat's accommodation is managed along with temperature and air changes. Obviously when the weather is good one wants to open the boat up as much as possible but if we are going to live aboard during a cold damp winter or a very hot and humid summer we will rely on the systems to give us a comfortable living environment. My intention is to be able to lean back in a reclining chair and read a book in comfort while the rain pours down or the mist rises outside, just like I do in my house.

You asked what sort of boat we are going to build. All I can say at the moment is that it will be an offshore motor cruiser and we want it to go to certain places which impose these limits:
  • Beam <5m
  • Overall length <15m
  • Draught <1.8m
  • Air draught <3.5m
Our current boat is a motor sailer and the new boat will take over when we retire from sailing. I am at stage 1 - writing the performance specification which will say where we want the boat to be able to go and what we want our life aboard to be like. Stage 2 turns that into a very detailed specification which will include our preferred component suppliers (everything from bilge pumps to the cooker), and possibly some sketches, which a naval architect can accept as a brief. I envisage completing stage 1 by Christmas 2015, stage 2 the following year, having drawings and quotes in 2017, and perhaps building the boat in 2018. I have been through this sort of process with other big projects and I know that if I rush this stage we'll have a lot of grief later on.

Up to now the only aspect of the preliminary specification which has caused me any problems is the insulation. This affects the thickness of the accommodation envelope, which in turn affects the amount of internal space, and we have some fairly demanding requirements for the amount of space we want. Insulation isn't a trivial point - it's fundamental.
 
TwoHooter said:
rustybarge - Thanks for your reply. I agree with what you say. Your point about interstitial condensation is very relevant. The accommodation will have effective insulation and vapour barriers on all 6 surfaces. I just don't yet know how best to achieve that.

Concerning de-humidification I think the best approach is to use an integrated HVAC system so that the humidity in the boat's accommodation is managed along with temperature and air changes. Obviously when the weather is good one wants to open the boat up as much as possible but if we are going to live aboard during a cold damp winter or a very hot and humid summer we will rely on the systems to give us a comfortable living environment. My intention is to be able to lean back in a reclining chair and read a book in comfort while the rain pours down or the mist rises outside, just like I do in my house.

You asked what sort of boat we are going to build. All I can say at the moment is that it will be an offshore motor cruiser and we want it to go to certain places which impose these limits:
  • Beam <5m
  • Overall length <15m
  • Draught <1.8m
  • Air draught <3.5m
Our current boat is a motor sailer and the new boat will take over when we retire from sailing. I am at stage 1 - writing the performance specification which will say where we want the boat to be able to go and what we want our life aboard to be like. Stage 2 turns that into a very detailed specification which will include our preferred component suppliers (everything from bilge pumps to the cooker), and possibly some sketches, which a naval architect can accept as a brief. I envisage completing stage 1 by Christmas 2015, stage 2 the following year, having drawings and quotes in 2017, and perhaps building the boat in 2018. I have been through this sort of process with other big projects and I know that if I rush this stage we'll have a lot of grief later on.

Up to now the only aspect of the preliminary specification which has caused me any problems is the insulation. This affects the thickness of the accommodation envelope, which in turn affects the amount of internal space, and we have some fairly demanding requirements for the amount of space we want. Insulation isn't a trivial point - it's fundamental.
Click to expand...

What is a hvac system?

Are you thinking displacement speed or faster? If you're interested in a planing boat have a look at Rob71's boat build on this forum:http://www.ybw.com/forums/showthread.php?374141-Fifty-Feet-of-Grey-(steel)
 
PS: forgot to mention that a custom design from a recognised naval architect will cost about £15-£20k....plus!
 
rustybarge -

HVAC stands for Heating Ventilation and Air Conditioning. Most modern air conditioning systems incorporate humidity control.

I think it will be a displacement hull. I have pencilled in a cruising speed of 8 knots, maximum speed 12 knots.

If the finished boat costs £250k then the fees you suggest would be less than 10% of the total cost. But I'll haggle when the time comes!
 
If you get a custom built 15m boat for £250k don't publicise it as there will be a queue round the block of willing buyers.
 
TwoHooter said:
rustybarge -

HVAC stands for Heating Ventilation and Air Conditioning. Most modern air conditioning systems incorporate humidity control.

I think it will be a displacement hull. I have pencilled in a cruising speed of 8 knots, maximum speed 12 knots.

If the finished boat costs £250k then the fees you suggest would be less than 10% of the total cost. But I'll haggle when the time comes!
Click to expand...

12kts in a 50' hull would make into a semi-displ. Hull; to build this hull form in steel is very hard to do because of the curved surfaces, and steel is very very heavy meaning that a s/d hull will need massive power to reach 12 kts.
Rob71's 50' hull weighs over 20tons, and I think he's fitting twin 600hp to get 20kts/33gals/hr....in other words a s/d steel hull will be limited to being a fast displ. Hull unless you are willing to throw mega horsepower at it.

so you will probably have to settle for 7kts cruise with less than 10kts flat out with twin 150hp diesels or thereabouts. I'd choose a single 300hp for simplicity sake.

You should be able to build a very nice boat for £250k.

sounds like a very interesting project. :)
 
Thinnest insulation for equivalent u value would be aerogel but it is very expensive. May be useful for where space is at a premium. Other types include rigid EPS (polystyrene) and PUR (polyurethane). The former can be treated with carbon for greater insulation but is thicker than PUR. PUR does off-gas and so its insulation value decreases over time. You can get open or closed cell. Closed cell is supposed to resist damp more. You can get various spray on types including PUR and more environmentally friendly cellulose based types. They have the benefit of acting like a vapour barrier if closed cell. They prevent access to the hull material obviously. You already know about vapour barriers which must be on the warm side of the insulation and must have close attention to detail.I think many people prefer the spray on for ease of application.
 
I've been down this track with the Bertram (btw if you really want the performance you listed you will need a semi displacement hull. Look at the Bruce Roberts Waverunner designs) You will also need at least 450 HP to build a bow wave at 12 knots, or run slower on a smaller engines and fit stabilisers.
You have said nothing about noise insulation. If you spend more than a few weeks afloat you'll find that the constant slap of waves against the hull will drive you mad. Especially when you're socked in and the weather is miserable. And yes it does get like this in the Med.
So when you run down the list of options, the only material that will provide thermal and accoustic insulation is high density sprayed closed cell polyurethane foam. 50 mm might be enough but I would go to 60 mm. I would also have the internal plywood laminate skin lined internally with aluminium foil.
Double glazing is a nice to have but security against leaking and integral mosquito nets are more important. Truth is that the windows are more open than closed and the bugs are everywhere. Learn to live with humidity because unless you plan to live in a bubble or Superyacht, you will waste a fortune trying to avoid it.
We have aircon and climate control system on board (Cruiseair) but only use them for a few nights each year. We've found that aircon builds a trap for you. The more you use it the more you need it, and that stops your body adjusting to the local climate, making life even more uncomfortable when you go out and about.
If you're planning a canopy over the aft deck, which is an absolute necessity for a long term cruiser, then again accoustic insulation is vital to control the attenuated noise and vibration from your exhausts. As is wrap round weather proof tarps for wet weather and storage also a real must is wrap round light weight bug/ sun screens.
It's a great project and good luck but before you sign any contracts spend money on chartering a boat the size you intend to build and spend two or three weeks trying out your concepts.
Wish I was doing it, good luck
 
rustybarge - Thanks for your advice. I shouldn't have been drawn in to saying what full form or speed I want at this stage. It will almost certainly be a slow boat. We won't be using it to do quick weekend trips to France or anything like that. As for the cost I really don't have a budget at this stage. I know it will cost a lot!

pmagowan - That's a really helpful reply - thanks a lot. I had not heard of aerogels before: steep learning curve. I am now studying the data sheet for Spaceloft by Aspen Aerogels - very interesting properties.

Bertramdriver - Another really helpful reply. Thanks hugely! My draft specification says only that we want to be able to cover a passage of 125 miles in 24 hours so in still water that would be just over 5 kts. I expect there will be other things on my wish list which turn out to be as impractical as 12kts. Your comments about double glazing are also very helpful - I wonder whether it's feasible to have double-glazed leak-proof opening windows with insect screens! Oh well, if you don't ask you don't get. I understand what you are saying about humidity control - our daughter lives in the Caribbean - but I really do want to keep the interior of the boat dry during the British winter. Chartering a boat as a try-out is a good idea. I suppose some time next year would be best for that.

I suppose I should have begun this thread by asking why most boatbuilders don't insulate their boats to the high standards. Is it because of cost, or technical difficulties, or lack of market demand, or what?
 
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TwoHooter said:
I suppose I should have begun this thread by asking why most boatbuilders don't insulate their boats to the high standards. Is it because of cost, or technical difficulties, or lack of market demand, or what?
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Probably all three. Boats are mostly sold as toys for occasional use - not for full time living, although of course many people do live on them full time. They either adapt the boat as far as they can to suit their requirements or adapt their way of living to suit the boat. Either way can result in an acceptable compromise as the alternative of doing what you plan is either technically difficult and or expensive. You will however, find examples of custom built boats designed for living in extreme conditions, mainly those intended for high latitudes. Standard boats are much more easily adapted to warm or hot climate environments, which is where most liveaboards tend to spend their time.

You might look at some of the Scandinavian deck house saloons as they tend to build for use in colder, damper climates and insulation, including double glazed windows is higher on the list of priorities than boats built for southern Europe.
 
http://www.theyachtmarket.com/boats_for_sale/836876/?searchid=8371771&page=30

Nice plans you have... however, I doubt you will have a custom vessel at anywhere near the price point you suggest.

Just as a thought, look at the link above. Additionally, if you research Dutch mobo builders, you will find them in the multi million price range....

Best of luck with your project and PLEASE let me know where you can get a 50 footer custom built at your suggested price point.
 
TwoHooter said:
One of the reasons for building our own boat is that it has to be capable of being a home in all European climates including cold and damp (English winter) and baking hot (Greek summer), therefore it needs to be very well insulated. Ventilation and de-humidification are also important, but if the insulation is wrong we will be fighting a losing battle from the outset. I am amazed at just how badly insulated many modern boats are, including boats costing hundreds of thousands of pounds - it is one of the reasons why we are self-building.
Click to expand...

Should you consider buying a house?
 
Beam <5m
Overall length <15m
Draught <1.8m
Air draught <3.5m

At that size and on a standard round bilge displacement hull you should get a hull speed of 8 knots with 7 knots easy cruising with a 300 hp engine, so 4 knots looks a bit unambitious and would give an uncomfortable ride unless stabilisers are fitted.
If you go the semi displacement hull route you'll get the economical hull speed in slack seas plus an option to easily manage 20 knots with 2 x 400 hp. Believe me the ability to fly over sloppy seas and get back quickly when a front blows in is well worth the cost of the fuel and the ride is more comfortable. Yes you do go faster when the waves pick up, at least to a 5-6.
I'm sure planing hull Mobo owners will have advice to offer.
 
A personal experience of insulation from living aboard a steel yacht for 15 years.

We insulated throughout down to the waterline with slab polyurethane foam: 50mm in the form of 2 layers of "Eurothane", with 3 layers around the windows and refrigerator. It was wedged between the hull/deck and the wall/ceiling panels. This provided first-rate insulation inside, warm in winter, and in summer far cooler than GRP yachts even when the deck was too hot to touch. It did, however, reduce the internal volume very significantly. It was possible for us to use a slab material because the hull and deck were hard chine, only very slightly curved. We rejected spray-on foam because it would be impossible to keep the inside of the hull and deck under scrutiny for rust - a decision for which we became very thankful as the boat became older. We only insulated down to the waterline because we assumed that the internal temperature of the yacht would then be regulated by the sea temperature outside. This worked well in the UK and many parts of the world, but we found in some places like Canada sea temperatures are very low in winter and it was not a good solution there.

We kept port size to a minimum: double glazing was not an issue. Our primary concern was that the ports were strong enough to cope with serious gales in open ocean. If you've seen a port punched out by a breaking wave, you'll know what I mean.
 
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I echo Vyv Cox's advice; I think you are greatly exaggerating the issue of insulation. We've cruised in arctic waters, and have slept aboard throughout UK winters and are now planning a jaunt to cold regions in the south, and we've done little to modify the plastic boat we have.

- The cabin simply does not have surfaces which are directly touching the hull. There are cupboards or lockers, or floors with tanks or storage everywhere.
- The ceiling will be insulated anyway as it's normal practice to use a sandwich construction and it's usually 50mm thick and lined as well. This is done for stiffness rather than thermal reasons, but it works anyway.
- The windows are small in any ocean going boat, so again double glazing isn't usual. We put black-out material (cut from dark grey camping mat) into the recesses when we want more insulation or to cut out the (24 hour) daylight.
- Unless you've a humungus yacht the cabin volume is tiny compared to the living room in a house, so heaters are over powerful and one finds oneself flinging open hatches even when outside it's 10 degrees below!

I can only speak for plastic boats, not for steel.
 
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