Insulation of a boat for year-round residence

– Hvordan slipper man af med kondensvand?

Why insulate a boat that is already warm enough?

An ordinary yacht has a small outer surface and can be heated, regardless of how much insulation there is in the boat.

Therefore the main purpose of the insulation is comfort and no condensation, i.e. the surfaces must be kept above the dew point.

If we e.g. assuming we have a relative humidity of 50% (22 degrees), this means that the surface must be warmer than 12 degrees.

How do you do that?

In our boat, I have chosen to put 38 mm insulation material on all available surfaces. That is especially coffin benches and cupboards. And then I have led the radiator water through the coffin benches in uninsulated pipes.

Less might do, but the above is enough.

Insulation material

The insulation material must be so flexible that it can be glued to double-curved surfaces, and it must be vapor-tight. I have chosen Armaflex, but K-flex is roughly the same product.


Armaflex has a self-adhesive adhesive surface on one side that sticks very hard. In order to be able to control the application, I have chosen to apply it in two layers of 19 mm.

To get a nice surface I have:

  1. glued the Armaflex to the hull using contact glue (the built-in adhesive surface upwards).
  2. The next layer is now glued using the first layer’s built-in adhesive surface.
  3. At the top I have put a layer of ceiling vinyl, again glued with a second layer of adhesive. Result – a nice and robust surface.


The price differs from country to country, e.g. it is much more expensive in Denmark than in Germany
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