Chrome-plated insulation!
I am digging that silver foam insulation stuff. We are building a C44 for a client in south Florida and started putting that stuff all over the boat, under the deck, inside the hull, under the coachroof....
The mistake is believing the advertisers' hype that it adds anything considerable to the R-value; it doesn't; it can't because it requires air pockets to either side to be effective. But what it does much, much better is to passively block heat transfer by virtue of being reflective. It will actually work both ways-- keeping heat out, keeping heat in, especially not allowing one to transfer to the other, so it's good in two seasons or in two climates. This will help cut down on hull sweating ('cold iced-tea glass syndrome') and thus humidity and mold. It is also helpful against sound, no small matter for those of us who sleep so close to the waterline.
I decided on the bubble-wrap stuff at Lowes; this (with the electrical system postponed over the vicious NJ winter) is my next major project.
