Beadboard for Hull Insulation?

[ps02210]

I'm about to insulate my boat throughout and was going to use extruded foam (XEPS) but have a source of essentially free 1/2 inch beadboard (MEPS) that I'd prefer to use to save on expenses.

I've read, though, that the bonding agent in beadboard can absorb water over time and am wondering (a) how big a risk that really is in this particular application, and (b) whether that was a problem with earlier formulations but not with the current stuff.

I anyway intend to paint over the insulation with a water based latex in most areas, and am thinking that between the contact cement on the hull side and the paint on the other side, that may serve to sufficiently minimize any absorption that otherwise might occur.

Eh?

 

[BAtoo]

From doityourself.com

Molded Expanded Polystyrene (MEPS) Foam Board:
MEPS is a closed-cell material that can be molded into many everyday items, such as coffee cups and shipping materials, or into large sheets as construction insulation. This material is commonly known as "beadboard," and it has an R-value of about 4 per inch of thickness [2.54 cm].
To make beadboard, loose, unexpanded polystyrene beads containing liquid pentane are mixed with a blowing agent and poured into an enclosed container. The mixture is then heated to expand the beads many times their original size. The beads are then injected into a mold and under more heat and pressure expand to become foam blocks that are then shaped as required.
The physical properties of MEPS vary with the type of bead used, but the density of the board is usually one pound per cubic foot (16.3 kilograms per cubic meter.) Beadboard is manufactured at various densities, depending on the application. Beadboard for roofing materials has to be dense enough to walk on without damage. Wall insulation boards are several times less dense than roof boards. R-values range from 3.8 to 4.4 per inch (2.54 cm) of thickness. Since spaces between the foam beads can absorb water, a vapor diffusion retarder is necessary if water transmission through the insulation might present a problem for the user.
MEPS foams are also available as small beads of foam too. This type is often used as a pouring insulation for concrete blocks or other hollow wall cavities. However, be aware that poured beads are extremely light-weight and take a static electric charge very easily. They are notoriously difficult to control and any wind at all often results in the beads flying all over the place. Also, if there is ever a hole in the wall the foam beads will continue to fall out of the hole until the wall is almost empty of beads


Read more: http://www.doityourself.com/stry/foamboardinsulation#ixzz13l4VJ0q0

Seems as though there is no bonding agent but water vapour can permeate. Good R-value. Painting both sides and the glue may be enough.....