Jim Rudoff: Green Construction & Remodeling


Part II
In Part I (published in the April issue of the Courier), I introduced some green building concepts and went into some detail about photovoltaic solar systems, air quality and costs. Part 2 is all about hot water. We’ll explore tankless or on-demand water heaters as well as solar hot water systems. Features like these that reduce energy costs can increase the marketability of your home, especially in San Francisco, where there’s a significant interest in the environment.

Why pay to heat water that sits in your tank while you’re at work or on vacation? With a tankless water heater, you heat only what you need, and you’ll never run out of hot water! Today’s tankless water heaters are automatically variable, meaning that if you’re washing your hands they’ll heat just enough water for that task, while if you’re filling a tub and washing your whites there will be plenty of hot water for both. This is a highly efficient design. Larger tankless heaters are almost always gas, while small, sink-sized heaters are often electric.

The cost of a house-sized tankless heater is comparable to a new, full-size tank heater, and can cost far less to run on an annual basis, providing nearly instant savings. Be aware that always having plenty of hot water is both a blessing and a curse: there’s no built-in incentive to keep your showers short, so some households actually use more water after installation (though they still save on energy costs).

Tankless water heaters are sometimes incorrectly called instantaneous water heaters. The problem with this is that they aren’t instantaneous at the tap. There’s a slight lag while the water is heated, followed by another lag while the cold water that’s already in the pipe between the heater and the tap is cleared (usually down the drain). There are several ways to address this issue. First, tankless water heaters can be small enough that some people place them at each sink. Though slightly less efficient than a larger unit, this nearly eliminates lag and water waste. Additionally, in new construction, you only need to pipe cold water to the taps, thus cutting your plumbing expenses nearly in half!

In a remodel, where the piping is already in place and you may not be able to place the new tankless heater any closer than where the old tank used to be, you can install an on-demand recirculating pump. A moment before you step into the shower, simply push a button mounted near, for example, your towel rack. A pump pulls the cool water that’s sitting in the hot water pipe as if you had turned on a tap, but instead of dumping it down the drain, it goes back into your water supply. The pump automatically shuts off when the hot water reaches it, indicating that your hot shower is ready. These pumps are small and inexpensive.

Let’s use my own home as an example. Since my flat is on the top floor and my hot water currently comes from the basement four levels down, I have a great opportunity. I have attic access, and both my bathrooms are near my kitchen, which means that all my hot water needs are close together.

Photovoltaic (PV) panels – those familiar black solar panels – are used to generate electricity. Which is great, but it’s only one way to capture the sun’s energy. Using the sun to heat your hot water may be a better choice for San Franciscans because it works even on overcast days. Like a PV system, it can be fairly expensive to install a solar hot water system, with a payback as long as seven years, though San Francisco’s recent solar incentive program may bring that down.

Because solar hot water systems need a backup, especially during the winter, you might want to install a tankless hot water heater at the same time as your new solar system. Some vendors integrate a gas or electric booster into their systems. If you are building a new home or your remodel is significant, you may even be able to use the hot water to heat your home.

Jim Rudoff, GRI, is a green Realtor and Duboce Triangle resident. To reach him or subscribe to his complimentary newsletter, call (415) 296-2102, e-mail jim@jimrudoff.com, or visit jimrudoff.com. The first part is on-line in the April ‘08 issue at castrocourier.com.

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