Major condensation in loft space
Discussion
Equus said:
tolmie35 said:
...one side of loft bone dry and one wet, dripping from felt....
That's screaming 'microclimate' at me.There are two mechanisms to be aware of: solar orientation is the obvious one (the side of the roof that gets the sun will be warmer, and less prone to condensation), the other perhaps less so...
I've mentioned on other threads (but not this one, it seems) that part of the problem can be aerodynamic. A pitched roof acts like a very crude aerofoil to the wind flowing over it: a low pressure bubble forms over the lee slope. Low pressure = low temperature, so the airflow cools the roof structure, causing condensation on the inside surface. In this case, increasing roof ventilation actively and very dramatically makes the situation worse, as you're just feeding a nice, continuous flow of damp air across into the roof to have its moisture condensed out.
Obviously, the 'perfect storm' is where you have a roof slope that is both north facing and in the lee of prevailing winds, so I'd be checking both those things as a possible cause.
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