Hi Cal28- I'm no expert on insulation or condensation
management.... but here's what we did to make our V-berth area livable in the Pacific Northwest
(also a bit cold and damp):
The first thing we did was put a small dehumidifier in the v-berth compartment... one of the small aluminum
round things that only get warm... the one we use has a small fan also. It did wonders in changing the climate forward. However this only works at the dock
The next problem we tackled was keeping the sheets
and bedding dry from condensation through the hull. Our mattress already has good ventilation underneath... make sure you do that... use either dry-deck or other material to lift
the mattress off the support and allow airflow under.
We took a scrap of blue-board insulation and placed it at the foot of the berth, up against the anchor locker
. The sides of the berth are lined with the reflectex insulation, tight against the hull.. Ours remains in the in-style 'silver-bubble' look. Quite trendy. We then have dry-dek between the insulation and the bedding, to allow for a bit of airspace.
With the airflow around the mattress, the insulation around the v-berth, and keeping the bedding from contacting the hull.... we've pretty much licked the condensation problem in the v-berth area. We also put some of the reflectix insulation against the forward hatch
.... we just cram it up against the plexiglas and it stays in place. Keeps condensation drips from landing on our heads as we sleep.
The other keys are to keep moisture to a minimum down below, but you are probably already doing that.
As for putting fabric around the insulation... I don't have any experience with that. Keep in mind that you want to minimize any material that could absorb moisture and then mold
My advice: get good airflow around the mattress and bedding... the sides and the bottom. Insulate the sides of the v-berth with reflectex... one or two layers would be fine. Pay attention to the foot, if you have an anchor
locker.. it will be have cold air in it, and will condense at your feet. And if you're living aboard
, a couple of small dehumidifiers.
Let us know what ends up working for you.
(not dealing with condensation at the moment... in the Sea of Cortez)