We decided to put the hot water heater outside the house in its own little shed (the not-yet-stained structure seen peeking out from behind the house). With a high water table, we can't have basements in Florida. We're running insulated water lines to the house and to the radiant heat system.
Pictured here is the manifold for the radiant heat system, common in the northeast, but not down here in Florida. Because our AC man was doubtful that warm water in the slab could heat our house, he insisted that our AC system have a heat pump for backup. I know, you First Day builders who live in the ice and snow are rolling your eyes.