Update: The home sold for $450,000 in August of 2020

It’s tough to call a single-family mansion on the North Shore a green investment. But whether it’s truly eco-friendly or not, 596 Clavey Lane can claim better energy-efficiency than when it was built in 1993.

That’s thanks to an alternative-energy entrepreneur who bought the Highland Park home in 2006, two years before we wrote about it in this magazine. He tried to shrink its considerable carbon footprint — and utility bills — by retrofitting it with equipment designed to harness solar and water power.

But even a geothermal energy system couldn’t save this home’s value. It was foreclosed on last year, and last week, a real estate investment trust listed it for $589,000.

That’s $2.2 million off its asking price of $2.79 million five years ago — an 80 percent discount.

Why the steep decline?

For one, it’s not the best time to be selling a big-ticket home on the North Shore. Just ask ‘80s balladeer Richard Marx, who recently sold his Lake Bluff estate for $4.2 million, nearly $14 million off its original asking price.

The house also has some issues, to put it mildly. The broker, Todd Emert of Dreamtown, claims it’s “not in good shape.” The basement in particular will need to be gutted, thanks to 18 inches of standing water and black mold growing on the walls.

Depending on your personal taste, the rest of the house could use some TLC too. The voluminous front room evokes a community college atrium, the fireplace in the master bedroom is jarringly off-center, and the carpets give off a dank, dorm-room quality. There’s even a bathroom with floor-to-ceiling mirrored walls.

“It’s the ugliest place I’ve had to sell,” Emert admits.

But think about that electric bill.