Hey John
 

My iPad hard on LMFAO

duct.jpg

Dang you got an app for that? What ever happened to figuring CFM and duct based on room size etc. Then add the whole shebang and figure trunks, returns and air handlers.

It's only a duct slide rule. All the ones I've had I've ended up giving out over the years, but not this one LOL

Manual J and D are still around and used regularly, although it's been a cow's age since I've done one "long form" and not use the computer.