The dryboards (?) in my summer house are starting to crumble. They have been here for at least 50 years, without any issues, but ever since no-one is living there permanently (4 years ago), they are falling apart.
It looks like humidity-related to me, and I am afraid that if I replace with the same kind of dryboard, I'll get the same thing quickly. Is there anything more appropriate for this context?
Inside the house, I measure:
Winter: 7°C / 44°F - 50 to 60% relative humidity Summer: 20°C / 68°F - 60% relative humidity
Edit: Layout to better understand