I read about a passive recirculating system using a purpose-built valve for a second-story bath. Will this work on a single story?
I know firsthand that earlier versions of passive loops didn't work all that well on a single story, but I am not familiar with current models. Now I use an on-demand circulation pump. That is the most energy-efficient way I have found to circulate domestic hot water, because you only use it when you need it. If you need it constant, then of course, this doesn't work for you. You probably will need to use a standard hot water recirculating pump on a thermostat. If you can do it, however, the most efficient germinating bed I've found is fresh manure laid below the beds.