Hull Insulation

[SkiprJohn]

I have an opportunity to add insulation in places on the interior of the hull.
I've read From and Bare Hull and This Old Boat about the subject but it doesn't go into how far down in the hull should I be insulating. I suppose down to the top of the bilge but can't find it in writing.

So how far down the interior of the hull should I go with the insulation?

Is it also advisable to insulate the interior of a lazerette or other lockers?

Any answers will be helpful. I don't intend on spending many winters in cold climates but a few might have to happen.

Kind Regards,

John

[Alan Wheeler]

For insulation to work effectively, it is all about stoping transference of energy. So you insulate in a way to provide a protected environment where you are living.
Condensation is a big problem, but it can be overcome. It is a case of having an air gap between the hul and the insulation so as air movment can be provided. Stay away from spray on foams and insulation products being glued to the hull. If possible, provide a "false" wall of timber between the hull and insulation and stick the isulation to that. Simple light weight ply is sufficient. ensure you have air movement from bottom to top behind the panel. Any condesation can run down to the bilge and evaporation can carry moisture up.
A well insulated boat can aid in both hot climates and cool. But unless you are heading for very cold climates, most boat heaters will keep up with maintaining a good climate inside the boat without the aid of insulation.

[Zach]

What sort of insulation is best on a boat?

We're currently refitting an old wood boat. (Old 83 footer coast gaurd cutter with a cabin built.)

When the wheel house and cabin was built they used a fiberglass insulation like you would use in a house. Is this the correct product on a boat?

Trying to get enough R factor out of a 4 inch thick wall to make cooling easy sure is challenging!

[hellosailor]

"When the wheel house and cabin was built they used a fiberglass insulation"
In board and abovedeck that might work but I'd be afraid to have it on a boat. Think about what happens if you get trapped moisture, followed by molds and mildew. UGH. And if that insulation was used against the hull, I'd be sure you'd get condensation in it, to be followed by toxins. I'd rather use a closed-cell material fully bonded to the hull (with adhesive) or a spray-on urethane which, again, is closed cell and bonds itself to the hull. Yes, that makes it impossible to access the hull directly without ripping off insulation. But how else can you ensure you won't be growing molds in it, unless you leave out the insulation and use traditional open slats, etc. for ventilation?

[Zach]

I was figuring that it would act like a sponge, but havent figured if a block type (styrofoam or the like) insulation would work better... instead of total saturation, pockets of goop that would be trapped?

[hellosailor]

Styrofoam is closed cell, afaik, but not flexible. You'd still have problems bonding it to the hull, or ventilating the voids behind it. I guess you could use foam to adhere it in place & fill behind it but then you're also making one job (i.e. just foaming) into two, foaming plus cutting & trimming & fitting.

[DeepFrz]

Steve Dashew has a good writeup of insulation and what he chose for his un-sailboat.

http://www.setsail.com/dashew/do_PARADIGM.html

Scroll down the left and look for "hull insulation".

I don't agree that there should be a gap between hull and insulation. Between insulation and interior joinery yes, you need airflow.

Deep

[SkiprJohn]

Ok, now I am of the assumption that I can used styrofoam down to the waterline for insulation. My hull is fiberglass so don't have to worry about moisture on steel so could probably go down to the bilge?
Epoxy holds styrofoam to the fiberglass hull pretty well if I can get the stuff to bend.

Any other suggestions?

Regards, --John--

[hellosailor]

"Epoxy holds styrofoam to the fiberglass hull pretty well if I can get the stuff to bend"
But you can't get it to bend unless maybe you get thin sheets that are flexible enough and layer them. And urethane foam will be cheaper than epoxy, with the advantage that it foams and fills gaps. If you can bend it, cheaper adhesive and a notched trowel might work.

[Boracay]

The last boat that I looked at buying had polystyrene foam blocks shaped and glued to all visible steel above the waterline.
It seemed to be a quick, effective and cheap way of insulating a steel boat.
Linning a hull using conventional methods can be very expensive and time consuming and restricts access to the hull.
If provision was made for the "skin" to be removable then access to any part of the hull is possible.
Applying any type of insulation assumes that the hull material is properly protected. (ie good paint for steel, epoxy for wood, gel coat for fibreglass etc.)
I would favour leaving a small gap between the insulation and the hull so that any liquids can drain.
A much larger gap would be necesary below the waterline.
I used to think that burning polystyrene produced toxic gases but this suggests it is no worse than commonly used materials :-
http://www.aeromfg.com.au/html/styrofoam_msds.html

[Alan Wheeler]

It does produce toxic fumes and in huge black quantities meaning the major toxic affect is that you simply can not breath. The smoke is thick heavey and choking. A lung full of that stuff and you are dead.
And it does burn crazy out of control. So you do want to be aware of fire risk.
But then, fibreglass will burn the same way once it is ignited. Fibreglass takes a little more to get going than Styrene does though. Styrenes are highly combustable.