Driving Rain Moisture Source Roof/Wall

[Mark Jimmy]

Hello,
I am trying to simulate rain leakage in both walls and the roof. As recommended by ASHRAE 160 a 1% driving rain leak is placed within the assembly. I have the driving rain set to be calculated by ASHREA standard methods. I have found that both the roof (0 inclination) and the wall (90 inclination) have the exact same amount of moisture placed within the assembly. I.e. the 1% driving rain leak is the same for both walls and the roof. I assume then that the driving rain of the roof is using wall orientation calculations (ASHREA method calculations). I was wondering if you could expand upon this.
Also for your information, I have selected no cut-off for the moisture source.
Regards,
Mark

[Christian Bludau]

Dear Mark,
thats because the ASHREA model does not handle the roof. So there is no reduction for a roof.
Generally spoken the amount of the 1% source is taken from the total amount, which is available for the orientation you have set.
Try to use the IBP model (unhook ASHRAE), there should be a different amount for wall and roof.
Christian

[Manfred Kehrer]

ASHRAE Standard 160 does recommend to use 1% driving rain leakage only for walls, not for roofs.
We had this week presentations at ASHRAE (https://www.ashrae.org/File%20Library/d ... -17-18.pdf last page) where we highlighted this amongst other things on how to apply ASHRAE Standard 160.