Insulation for boats: materials and methods

[rustybarge]

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.

As as a steel boat liveaboard, I second what you've said.
the vertical surfaces can be insulated with any old stuff.....it doesn't matter!

the ceilings are a different matter as even the tiniest drip of water is ALWAYS directly over head!

Spray foam is the only solution, how do I know?
i didn't do it!

you will also need to spray foam underneath the walkways if you have living space underneath like bunks etc.

 

[TwoHooter]

I am genuinely grateful for all the replies, but some people seem to have got the wrong end of the stick. I have never said that insulation is the only issue, or that lack of insulation is the only reason for rejecting existing boat designs, or that I don't accept that foam-core construction isn't a sensible method. I am writing the specification with a completely open mind, and it's a performance specification, NOT a design. I said in my opening post that ventilation and de-humidification are important, and perhaps I should also have said that we want a low energy input to the boat - this is simply good environmental and economic practice and really shouldn't raise any eyebrows.

"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" - yes but what about the hatches? Have you never experienced drips of condensation from the cold bridges formed by ceiling hatches?

"The windows are small in any ocean going boat" - (1) if you look at my original post I said we will be staying within European climates. We won't be ocean cruising. And we won't have small windows. I am specifying large windows so that we can enjoy the changing views. Otherwise we might as well follow Old Varnish's advice; (2) In our current boat we have experienced condensation on window and hatch frames, of all sizes.. I'm sure that was acceptable when our boat was built in 1985. I wouldn't find that acceptable on a brand new boat nowadays.

" 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!" - Our boat will have large living spaces, but putting that to one side how can it possibly be good design practice to specify a heating system which is so over-powered that you have to fling open the hatches when it's 10 degrees below? That's not just environmentally and economically unsound, it's just plain bonkers. Why not specify (and then design) a heating system that is carefully matched to the requirements of the users of the boat? Which is what I am hoping to do.

"the vertical surfaces can be insulated with any old stuff.....it doesn't matter!" Probably true, until you start considering questions of access for inspection, the possibility of attack by vermin and pests, ease of installing vapour membranes, longevity, fire risk mitigation, insurer's requirements, etc. etc.

"the ceilings are a different matter as even the tiniest drip of water is ALWAYS directly over head! Spray foam is the only solution, how do I know?
i didn't do it!" - That comment demonstrates exactly why I started this thread. I am thinking about insulation because I am pretty sure that if I don't I will have a wet head at some point and I don't want it!

As I said, thanks for all the replies, even from those who have given me the impression that they think insulation is a silly subject for a boat specification.