The new standard defines the "climatic" resistance of A, B, C. Each door is resistant at A level. Increased resistance B and C must be given on the door plate which you can usually find on the vertical side (at hinges).
Refer to the designer of your construction with your request. It is necessary to measure different humidity during the winter period by hygrometers over a longer period to get objective data.
There is no simple formula for such calculation. It depends on many circumstances which define saving. For example the difference in temperatures between two rooms.
taught us to make really good doors
know SAPELI, but our home is in the Czech Republic
All of them custom made
tested lifetime of our doors and components