Moisture Source: Fraction of Driving Rain

[kpnelson42]

I have heard that 0.02% is an general recommendation for a fraction of driving rain within "moisture source" to indicate a deficiency in the drainage plane… I am looking for an explanation of the rationale behind this number and when one might increase or decrease it when modeling...

Can you provide further clarification as to general "rule-of-thumb" percentages and when different values might be used?

Thanks in advance.

Keith

[Manfred Kehrer]

Dear Keith,

I don´t know where you got the 0.02%; the ASHRAE Standard 160 recommends 1% and thats what also typically use.