these things are not intractable but nobody has made a comment that fully captures the complexity. some in building science talk about smaller diameter pipes but code opposes it. There is so much to discuss. i’m tempted to launch into all of it but i think one interesting thing is the focus on hvac in the wake of the pandemic but not hot water as much. when the protocol for hot water hand washing is like 2 min or something but who omwould do that when that equates to 4 minutes total for waiting and washing. hot water is usually a joke and not nearly enough is being done for the basic code- all we have are schemes for select few.