Hot take: Manual J is overrated and 90% of resi guys don’t need it

Coming in hot. Manual J is great in theory and I respect the guys doing it religiously. But for resi swap-outs in existing homes with existing ductwork? You’re sizing to the duct system 9 times out of 10 anyway. The “”load calc”” becomes a CYA exercise.

Change my mind.

(Yes I know what the code says. Yes I know what ACCA says. I’m talking about reality on a service truck.)