WUFI

eordner · Post by **eordner** » Thu Jan 29, 2009 8:32 am -1100

I am modeling a wall with a rainscreen cladding system. I would like to simulate the vented cavity with the Air/Moisture Source. I can make the file with the air changes per hour, but I'm not sure what the appropriate ACH would be. Has there been any research done on this, and what do you feel is appropriate? Obviously, the ACH for a brick wall with ventilated cavity would be much lower than a true rainscreen. Thanks in advance for your help.

Achilles Karagiozis · Tue Feb 10, 2009 9:38 pm -1100

Rain screen walls most of the time are designed to provide equal pressure between the exterior facade and the air space. Therefore in theory negating the pressure driven moisture flows. They do not rely on air flow movement. They are vented not ventilated systems. Therefore they have less air flow changes in the cavity ventilation air space. The ASHRAE 1091 project can be purchased and essentially if you read all the 1000+ pages you can get accurate descriptions of air flow transport phenomena.

Suggestion, take 1/5th to 1/10 of the air flow of the ventilated brick and you will be on the safe side.