core water heaters. In cases where water use areas are separated by a great distance in the house, multiple cores can be built using separate trunks and multiple water heaters. According to Klein, overall system
efficiency is greatly impacted by the ef- fectiveness of the task—whether or not the customer is getting the desired result. “The big driver related to sustainable practices on the hot water side is that [system ef- ficiency] ends at the hot water outlet—the faucet, the shower.” says Klein. “If the plumbing in the middle is not effective in delivering hot water efficiently you simply can’t save as much water as you think you can.” Same goes for cold water lost waiting for hot—waste.
“The bottom line,” says Martin, “is minimizing the amount of water lost down the drain while you wait for water to warm up.” I can substantiate this. In our master bathroom, which is on the other end of the house from our (highly efficient, mind you) on-demand hot water heater, I run nearly four gallons of cold water down the drain waiting for hot water to arrive. Double that to account for another shower each day (that’s not even accounting for the teenag-
ers we’ll have in not too many years) and you’ve got more than 2,400 gallons of perfectly good water lost each year in my home.
In a retrofit situation like this, using a
demand-controlled recirculation pump on the far end of the house where all of the water uses are located (master and kid’s bath) would eliminate this loss. According to Klein, this strategy uses the least energy, wastes the least water, and is the most cost effective option for the application. Really, any strategy to address these
losses in retrofit is a good thing. Because, honestly, unless you’re focused on major rip-out-the-floors-and-walls retrofits, you’re not changing out the piping, you’re just replacing component parts. On the topic of retrofit—look for the leaks. The EPA estimates that about the same amount of water used for the people of Los Angeles is lost in water leaks each year.
Hot Water System Equipment Selection In the past, storage (tank) water heaters were the most common type of equipment. Recently, demand-based (tankless) water heaters have become more common, and both heat pump and solar water heat-
October 2010 GreenBuilder
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