Question: What do the following homes have in common?

• An 11,000-square-foot home in St. Charles, Ill., touted as “one of the greenest homes in the Chicago area.”
• A 5,100-square-foot home at Live Oaks Estates in San Rafael, Calif., marketed as green by an Eco-Broker.
• A 6,100-square-foot home in West Vancouver, British Columbia, aiming for LEED for Homes Gold certification.
• A 3,000-square-foot home on Block Island, R.I., aiming for LEED for Homes Silver certification.

Answer: All of these green homes have swimming pools. That shouldn’t come as a big surprise, since residential swimming pools are increasingly common in North America. Back in 1950, there were only 2,500 private residential pools in the U.S.; now there are over 7 million of them.

Although residential pools no longer raise eyebrows, they nevertheless deserve the scrutiny of the green building community. Let’s be frank: swimming pools are energy and water hogs.

Oink, oink
In homes with swimming pools, more energy is used to run the pool pump than anything else except the heating system and air conditioner. In fact, the typical California pool uses enough electricity during the summer season to power the average home for three months.

One study that looked at pool-pump energy use was conducted by Danny Parker, a senior researcher at the Florida Solar Energy Center. Parker monitored energy use at 204 Florida homes, 24% of which had swimming pools. On average, the pool pumps used 4,200 kWh per year. (For comparison, the average monitored home used 5,695 kWh per year for air conditioning and 2,227 kWh for water heating.)

I’ll need some water — lots of water
According to one source, homes with swimming pools use 58% more water than homes without pools. Another source reports that pool-equipped homes use twice as much water for outdoor uses as pool-free homes.

The typical backyard swimming pool holds 16,000 to 20,000 gallons of water. Pool evaporation amounts to 3 to 7 feet of water per year. For a 15 by 30 foot pool, the range is 10,000 to 23,000 gallons per year for evaporation, plus about 25% to account for splashing. If the pool is filled once a year, it requires about 38,000 gallons of water every year.

Residential water use varies from state to state, ranging from about 60 to 110 gallons per person per day — equal to 21,900 to 40,100 gallons per year. Compared to these usage figures, the 38,000 gallons of water needed for a swimming pool is a significant amount.

Green rating programs look the other way
What types of water-saving measures yield points under the leading national green building rating programs? Let’s look:

• The National Green Building Standard awards 2 points for the installation of an Energy Star dishwasher. That’s good, since Energy Star dishwashers use 4 gallons of water per load instead of 6 gallons per load. If such a dishwasher is used daily, it will save 730 gallons of water per year, or 1.9% of the annual needs of a swimming pool.
• The NGBS awards 8 points for the installation of an Energy Star washing machine. Also good: using an Energy Star clothes washer can save 7,000 gallons of water per year, or 18% of the annual needs of a swimming pool.
• The NGBS awards 1 point for the installation of a showerhead using fewer than 2.5 gpm. If a family switches to low-flow showerheads, they can save 2,100 gallons of water per year, or 5.7% of the annual needs of a swimming pool.

These measures are certainly useful, but they pale in effect compared to the benefits of not installing a swimming pool.

Surprisingly, both LEED for Homes and the National Green Building Standard are completely silent when it comes to swimming pools. As long as your home conforms to program requirements, you can put a big honking pool in your back yard, fill it to the brim with potable water, and run a 2-horsepower pool pump 24 hours a day — and still brag to your neighbors about your home’s green label.

Okay, folks, let’s get real
This is the part of the blog where I’m tempted to get on my high horse and denounce private pools — but I’m not going to do that. (A little voice in my head wants to say, “When I was a kid, we rode our bikes to the community pool …”)

Arguably, there are valid reasons for concluding that no pool-equipped home deserves a green label — although I won’t go there either. In my mind, there really isn’t any inherent problem with private pools. However, there is an inherent problem with green rating programs that pretend that pools don’t exist.

For the sake of consistency, any green rating program that grants points based on residential energy and water efficiency needs to consider swimming pools. If a home has a 20,000-gallon backyard pool hooked up to a monster pump, it makes little sense to worry about water-heater efficiency or kitchen faucet flow.

A modest proposal
Under the NGBS, each water conservation point seems to be equal to savings of anywhere from 365 to 1,050 gallons of water per year; let’s call it 700 gallons on average. With this calculation as a guide, I propose that any house without a swimming pool should receive 54 points under the NGBS scoring system, and that the minimum point threshold for bronze, silver, gold, and emerald compliance be increased by 54 points.

Under this proposal, homeowners could still have both a swimming pool and a green label; they’d just have to work harder — okay, much, much harder — at designing an efficient house to get there. Under such a scoring system, builders and homeowners would have a clearer view of the huge energy and water-use penalties associated with private pools.

At least two regional green rating programs — the Florida Green Home Standard and the Pima Country [Arizona] Residential Green Building Program — have decided to award points for homes without swimming pools. These programs’ scoring systems don’t fully reflect the enormous energy and water-use costs associated with pools; however, at least they’ve made a stab at addressing the pool problem. It’s time for the national programs to follow suit.

What about my existing pool?
If your home has a swimming pool, you can salvage some of your environmental dignity by taking the following steps:

• Consider installing a pool cover to limit evaporation.
• Use the smallest possible pump; most residential pools can get by with a 3/4-HP or smaller pump. An $800 investment in an efficient pool pump could lower your electric bills by $65 to $70 per month.
• All piping connected to the pool pump should be at least 2 inches in diameter. Pipe runs should avoid 90° elbows; instead, use gentler 45° elbows where necessary.
• Pool pumps should operate for only a few hours a day — ideally, 6 hours or fewer.

Last week’s blog: “‘Innie’ Windows or ‘Outie’ Windows?”