Hi Alberto,
1- "Normally it is said the typical threshold value of 80% but reading on internet it is said 90-95% as you see in the screenshot"
Could you put an example please about what you mean to analyse the in the mineral wool?
The table you are showing says in the header "...studies on mould growth
ON building materials". If you evaluate centimeters of mineral wool as you mentioned, the water content you are assessing is inside the mineral wool, not on the surface.
Or do you mean that the only way to assess risk mould growth or water run off on mineral wool is analysing the last rectangle/ bar grid by WRB for relative humidity (90-95% limit) and using 1cm thick ( outermost centimetre ) procedure ( link you sent me) when we use the water content ( instead of relative humidity) as variable to analyse the mineral wool ?
Yes, exactly, outermost element of mineral wool or also WRB for relative humidity.
Let's say that my roof would be safe the water content is below 120 g/ m2 because each degree inclination from 45 to 23 degrees is 3'6 g/m3 if my roof is 31 degrees ( from 23 to 31 is 8 degrees that is equal 30 g/m2). Is it right?
Generally yes, but unfortunately the standard does not tell clearly if the surface where the water runs off is in contact with an other material or not. I guess its a smooth surface, where the water will run earlier, than if the surface directly is in contact with mineral wool, where the water will be hold by the fibers longer before it runs off. We usually use the 200 g/m² given in EN 13788 for evaluating dew water formation in mineral wool. This value also corresponds with results from measurements we did for vertical facades. But with the values from BS 5250 you should be on the save side.
Merry Christmas and a Happy New Year
Christian
