The D'Mand system, installed under a sink, allows the user to bring hot water to the sink very quickly without wasting the water.

Over the past several weeks, I've written about water conservation as a strategy for saving energy and examined a number of water heating options. This week, we'll look at the issue of water waste while waiting for hot water and what to do about it.

This morning, at 33rd St and 7th Ave in the middle of New York City — right outside of Madison Square Garden and Penn Station — a 70-foot-tall digital billboard displaying a real-time running total of atmospheric greenouse gases was unveiled. The display reflects a measurement of 24 long-lived greenhouse gases (not including ozone and aerosols) named in the Kyoto and Montreal Protocols, and is based on Massachusetts Institute of Technology (MIT) research.

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Its website says:

Repower America is the bold clean energy plan to "repower" our country with 100% clean electricity within 10 years.

The Northeast Natural Building and Living Colloquium is a "conference" I go to every year. It's not everyone's cup of tea. No continuing education credits are offered. There's no high-power, big-project architectural, engineering, interior designing firm reps to hobnob with. There isn't a product expo in a cavernous auditorium. No suits, no ties, no shiny shoes. It takes place outside. You bring a tent to sleep in. Meals are provided (vegan).

Diagram of an electric water heater.

Twenty-five years ago, if you had predicted that I might be suggesting that electric water heating could be a good option, I'd have asked what you were smoking. I agreed with the argument that it's dumb to use such a high-grade form of energy (electricity) for such a low-grade energy need--a need that can be satisfied with renewables, such as solar energy or wood heat. I was also aware--and still am--of the significant environmental impacts of many of our power-generation options.

The press release says,

This partnership pairs a respected and independent source of green building information with a platform that enhances the usefulness of green product information.

It has become a truism that the U.S. is addicted to foreign oil. Heck, even George Bush owned up to it a couple years back. As we're trying to climb out of that addiction, are we about to fall into another? As a Greenwire.com article points out, a boom in clean and renewable energy sources in the U.S. could lead to a new dependence on imported minerals and metals.

In this photo, the indirect water heater is the large tank on the left.

Continuing our series on water heating, this week we'll look at two options for heating water with the home's central boiler. First some terminology: boilers heat water or produce steam for distribution in baseboard units or steam radiators, while furnaces heat air for distribution through ducts and registers. Integrating water heating with a standard hot-air furnace is not possible; if you have a furnace, you have to stick with a stand-alone water heater.