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Boat insulation

The insulation on my boat is between the roof ribs only, leaving the bottom of the ribs exposed causing water marks on the roof panals(one inch gap between bottom of ribs and roof panals),the builder says this is to allow for ventilation to carry the moisture away. But this is not happening as it is dripping onto the roof panals and penetrating through them leaving water stains. Should all the steelwork be covered with insulation?

Asked by: David Anderson  | 4.46pm, Saturday 29 January

WW says:

Most builders add a thin strip of insulation to the bearers, to avoid cold spots. That could be thin sections of wood, or an insulation material, like thin polystyrene (not anywhere near cabling!) or 3M Thinsulate.
The ventilation is needed, although unless there is (high and low level) ventilation provided behind the linings, it is hard to see how this would work in practice! Some builders do not leave an air gap, fitting the lining material directly to the insulation, which itself is attached firmly to the shell. This means that any condensation would have to form on the outside of the lining material (i.e. in the cabin) where it would evaporate easily. Also, it marginally increases the available space!

Mark Langley  | 10.41AM, Monday 31 January

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