We just lived our second winter on the boat in Sweden, without any major problems. We have two webasto heaters, one just for the after cabin and one for the rest of the boat. We do experienced some condensation but we open up the floor hatches now and then when we leave the boat for a couple of hours to let the air flow.
we also pulled out the madras a couple of centimeters in the guest cabin so it’s not tight to the hull.
A dehumidifier is a great help to keep the condensation in control.
this winter we experienced -22 C for about ten days without feeling cold inside, the heaters really makes it cozy.
in summer this is not a problem at all...
welcome up north!
Amel 54 No 165