Insulation, metal roofing and moisture

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Hi everyone,

I'm building a heated garden office with a box profile metal roof. This space will be heated during winter months.

I've got 145mm rafters with glass wool in-between. 15mm OSB ontop of the rafters, then Breathable roofing membrane. I've then fixed the metal roof directlu ontop of the membrane.

Should I have put some thin Battons in-between the membrane and the metal roof? Are the peaks in the box profile going to provide enough ventilation and stop water being trapped between the membrane and the metal roof?
An I worrying about nothing?

Thanks James
 
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The rule is, if you insulate a roof, a flat roof or between the rafters in say the pitched roof of your house, then the room needs ventilated and heated to stop condensation.

Then there's two ways to design/build/construct the insulted roof is either a cold a warm roof, as in, the positioning of the insulation and whether to vent or not.
 
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Breathable membrane for pitched roofs works by having an air gap on both sides of it.
 
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