Nobody buys boats based on insulation around here.. Never heard anyone discuss it. And almost all boats are solid glass/polyester with gelcoat. There are of course some foam composite boats too, but not chosen for their insulation properties.
When building the boat yourself it's of course a parameter to consider. Especially if you, for example, want to heat it with battery power. But the surface to heat is small. There's not really a problem with heating. I know a girl who have lived for years in a 28 foot monohull sailboat heated with a small radiator. No issue with being cold, she says. The ocean is always above 0 °C, so the gradient is not huge. That being said, I would of course tend to choose a slightly thicker foam in the WW hull if I would make my own boat. Would be good just to prevent condensation. But it's still going to be present at windows, so not sure if it's worth it. But I guess with a completely solar/battery energy source for heating it would be possible to have a dehydration unit running inside. And better insulation would reduce the consumption. But in the winter a diesel heater or electrical connection to the dock would be necessary still.
Do you imagine Steinar made decisions on his boat to have thicker sections of foam between the water and the interior? I wonder about his ww hull, but think it is mostly speed decisions.
Rob does solid glass for the radius of the corners. The foam tapers into and out of these radius as has been discussed That would be easy to foam fill post infusion, as has been discussed.
Steinar's lw hull is the older style rounded box with contiguous foam. Perhaps that's more appropriate for the cold?
How are Northern sailors/cuisers boats different?
How would you modify a HP for above the Arctic circle sailing?
Enclosed cabin with insulated doors seem to make sense.
The North has fresh breezes that even Rob could not tolerate for too long I imagine.