Hull insulation materials?

I beginning the finishing out of a 33' bluewater sailboat and will spend most of the time in the tropics. I would like to insulation the hull and deck against too much solar gain. Any suggestions on materials or methods?
Thanks

 

Colour of the hull, superstructure and deck is your best defense. WHITE. WHITE AND MORE WHITE


As for insulation...what material is your boat made of ?

 

Whatever the material of the boat and whatever the ocean you sail.. Armaflex.

 

This is the material I have on the boat.

A 32 ft boat is a different question. All insulation takes up preciuos space.

 

The hull is solid fiberglass layup. Deck is 3/4" marine plywood with glass/epoxy on outside surface. Paint will be white (slightly off-white). Here is what I am considering: 1/2" closed cell foam (Armaflex, K-flex, etc) then a aluminum radiant barrier then another 1/2" foam then either plastic laminate (formica, etc) where not exposed to the cabin or teak strips where exposed. Coach top sides and underside of deck the same but with plastic laminate and teak bats. Haven't finalized the deck surface yet - either treadmaster or teak strips.

Does anyone have experience/opinions on the radient barriar? What about the foil/"bubble wrap" that at Home Depo? Any good or a waste?

 

Teak on the deck, will jack up the temperatures considerably (30+ degrees). Even an off white will cause a 15 to 20 degree shift. White (bright white) is significantly better, though the glare is a pain in the butt at times.

Foil/bubble wrap is a good poor man's (woman's) choice. It's economical and easy to install. The really good insulators are costly, but do work well, given their thickness. The lower cost alternatives work, but generally you need more thickness for the same R value, so like everything in yacht design, it's a trade off. How much headroom can you afford to lose, what's your budget, installation ease, etc. all need to be considered.

If you elect to go the closed cell foam route, put the radiant barrier up first, then the insulation. The idea is to reflect the heat out, before it gets to the insulation, so the insulation has less "load" to deal with. If the barrier goes on after the insulation, then the heat travels through the insulation, hits the barrier and is reflected back through the insulation, which just makes it work twice as hard, so temperature differences aren't as great.

 

Excellent point Par on putting the radiant barrier directly to the hull instead of a layer of closed cell foam. Can I apply the barrier foil directly to the hull - contact cement - or do I need to have an air gap? It would seem that no air gap is needed as this is only for radiant solar gain, the foam is for conduction and convection. I have a sample of "atticFoil" coming but haven't seen it yet.

I think I will still use off-white as the tropical sun is bright!! I like the feel of a natural teak deck - no oils/varnish. Perhaps the natural silver grey will reduce heat buildup vs. an oiled deck. Treadmaster or equal is still on the table.

As you say - everything is a trade-off.

 

Contact cement works fine, though I'm fond of the mirror finished Mylars, compared to the foils and silver coated polyethylenes. The Mylars aren't cheap, but they are tough. You're correct, intimate contact is the proper way to go, with reflective barriers. The same is true of vapor barriers, though an air gap can be employed nearly as effectively on inert surfaces.

The difference between a nicely aged, silver gray teak deck and a bright white deck will be about 30 degrees in my summer sunshine. We're sub tropical here, but I've lived in the USVI's and the same rules applied there. An oiled deck will be slightly higher, maybe 5 more degrees. Really, the only thing worse than a teak is to paint it black. Off white will be 5 to 10 degrees warmer then bright white.

I'm not sure of your intent, but live aboards in the tropics, pretty much need A/C. There's a few ways to go on this, most costly a lot in fuel. One method I've used and blatantly stole from a Jamaican fisherman, is what I call swamp A/C. A small dirty water pump (12 VDC) is used to pick up strained water, from a hose dropped over the side of the boat. The hose is weighted to the bottom or lowered several feet and has a "J" bend which the strainer is attached, so it doesn't pick up mud and weeds. Water is drawn up and pushed through simple hot water, base board heater element(s). The water is returned overboard, while a small fan(s) blow (like seen inside a computer or amplifier) across the fins of the base board heater element.



These finned assemblies are placed around the roof perimeter and a sheet metal cover installed with louvered outlets or just holes, as in the fisherman's case. The water, even in the tropics, will be considerably cooler then the ambient air temperature and though not like standing in front of 25,000 BTU A/C unit, it will lower temperatures in a boat and cheaply. Small, low CFM fans are used, which make very little noise and more importantly draw very little current. Hot air goes in and cooled air comes out. It takes a while to effectively cool a large cabin, but if it's sealed up, eventually it does a reasonable job.

Well sealed cabin openings and of course insulation improves efficiency dramatically. The "swamp cooler" doesn't remove humidity, but can make life bearable. Real A/C is costly to operate in the tropics. Our total electric usage down here is 80% cooling needs.

As to insulation, again you have several choices. The best have intimate contact with the substrate, which removes air from the equation. Any air and you'll have temperature differentials that will cause condensation.

 

Personally I see no need for insulation on a small boat in the tropics. Perhaps under the deck. Why make your boat into an insulated oven that traps your body heat ? If you want to live civilized in the tropics you need a full length well conceived WHITE or light coloured awning to block sun and rain. Then you need a good ventilation system . Many Hatches and ...large surface area... mosquito screens . Ventilation could mean a electric fan that turbo charges the natural ventilation. or a WING SCOOP. Ive spent very much time in tropical conditions on yachts . I wouldnt compromise a small boat with insulation that may trap moisture, create a home for cockroaches or a rats nest. Obviously is you want a dual purpose boat for winter cruising or you have a metal boat insulation is worth the hassle.

 

The 3 mil aluminum and 1/2" foam arrived today - ordered from McMaster-Carr. Both products were much less money than thru any of the insulation speciality sites. The foam meets AMSE E84 burn/smoke of 25/50 which is quite good.

Par, excellent idea for a cabin cooler. I definitely will keep that in mind. thanks. I have 4 - 4" scoop vents on Dorads and 2 - 3" vents dedicated to the engine room (midship engine). Also have 4 - 7"x15" and 8 - 5"x12" opening portlights and a 24" square forward hatch. That should provide good ventilation. The boat is 33' overall with a small cockpit and large cabin.

 

A radiant barrier sandwiched between foam sheets prevents the radiant barrier from doing its job. The barrier needs to be able to radiate (reflect) heat into space, otherwise its just a membrane. A radiant barrier should be on the inside in cold climates and on the exterior in the tropics. Remember, cold is not a "thing", it is simply the absence of heat.

 

I'm contact gluing the radant barrier directly to the inside surface of the hull and coachtop. I'm putting the foam on the inside of the radiant barrier. My thinking is that the barrier stops - or decreases the radiant heat load (solar gain) and the foam provides for convection/conduction insulation.

 

That is probably better than putting the aluminum between the two sheets of foam but if the foil is contacting both hull and foam, it is still not a radiant barrier.

 

Have a quick chat with this guy.


VAN CAPPELLEN CONSULTANCY
P +31-78-641-1022
C +31-65-120-4253
E info@vancappellen.org

We use him for our mega yachts... Kyle

 

we would sell epoxy mixed with microspheres as in insulating coating for fire truck ladders and engine room ladders (after an engine room fire that made the ladder too hot to touch).

paul oman
progressive epoxy polymers inc.