My 55' alloy sailboat has 4" or about 100 mm of mineral wool insulation everywhere above the waterline. It is spun volcanic ash so does not absorb water
, is fireproof to about 2000f and is organic. Or so they say. I like it as I can weld on top of it without setting the boat
It is made by Roxul from Sweden
, I believe. The downside is that it is heavy and bulky. I put about 1000# or 450 kg of it aboard. A trade
off I suppose, as it takes a candle to heat the boat
now, and it is cool in summer.
There are many other products, I just did not want to add a lot of nasty chemical products into my living space.