I’m thinking of doing something similar to this. My workshop is built on a block foundation with a crawlspace that is a pretty constant 56 degrees year round. It’s only about 5 feet tall in the area under the CF, but, if I go from 1/2" air supply and use 1" copper on the verticals I think I get an effective length of 20 feet for each vertical. If I do this, however, I’ll need some sort of auto drain and I haven’t figured out how to do this inexpensively.
I certainly don’t want to go down there to open the drains! I’ve got spiders down there that growl at me!