I’ll just give it to you straight. Dry rot is a myth. Excessive dryness doesn’t cause it’s own special kind of rot. While this might seem intuitive for the layperson, it’s a pervasive misconception among those working in the building industry.
From Paul Fisette’s article on wood myths, ” Wood needs 4 things to decay: water, oxygen, food (wood) and favorable temperature”.
Dry is good for buildings. Water is bad for buildings.