For 10 years, Greg George, his wife, Kate Tunney, and their two tenants parked their cars on an L-shaped piece of slag-covered dirt behind their 1880s brick house on Mount Washington.

It wasn't pretty or very practical (snow shovels, plows and daily use scattered it everywhere), but it was kinder to the environment than the concrete driveway across the alley. Unlike most driveways and the asphalt the city recently installed on the alley, the slag was permeable, allowing rain and melting snow to percolate into the ground instead of running into the storm sewer.

About eight months ago, the slag was replaced with Eco-Tek interlocking permeable concrete pavers. Water now runs into the gravel-filled gaps between the gray blocks and down through two layers of gravel, seeps through the heavy clay soil and eventually finds its way into the aquifer, minus most of the motor oil, antifreeze and other impurities it picked up on the surface.

OK, so it's a "green" driveway. But how does it look? Nice enough that the couple and their 20-month-old son use part of it as an extension of their patio. And when they finish installing an ipe deck above it, it will be the base of a carport.

"I lived in Italy for a year, and I got used to a stone hardscape," Mr. George said. "This has a nice scale to it."

Spoken like an architect, which he is, an associate with Pfaffmann & Associates. Knowing that his wife is also an architect (for Rothschild Doyno Collaborative), you're not surprised to learn they're among the first residential users of Eco-Tek, which was introduced nearly a year ago by R.I. Lampus Co. (www.lampus.com), the makers of Omni-Stone. No wonder their neighbors had so many questions about their new parking pad.

"They said, 'What are you doing and why are you doing it?' " Mr. George said.

The neighbors got an explanation and a front-row seat as contractor Jason Kreinbrook of Kreinbrook Architectural Paving in New Castle removed the slag and slightly more than 1 foot of dirt before installing a permeable geotextile membrane, layers of No. 2 and smaller No. 8 gravel and, finally, the 3 1/8-thick pavers.

Since we weren't there, the rest of us will have to be content with Lampus' display of Eco-Tek and its other products at the second annual Design Fair for House and Garden, scheduled for Sept. 28 at the Priory's Grand Hall on the North Side. Bob Welling, vice president of Lampus' concrete products division, said a cross-section showing how permeable pavers work will fit well with the fair's green theme. Eco-Tek is already a hit with commercial and municipal users, he said.

"We saw a trend in the market. Many municipalities are demanding stormwater management plans, and most of those other systems are much more expensive."

Murrysville and other towns with fast-growing retail areas are keeping a close eye on the runoff from the huge parking lots around new development. Instead of creating elaborate systems to catch and hold the water, developers can install permeable pavement, some of which is made even greener with recycled materials. Lampus is coming out with a concrete building block that's made with recycled highway concrete and tiny shards of ceramic left over from the manufacture of dinner plates.

In the small but growing residential market, other permeable pavers include Oldcastle Architectural's Belgard Subterra stone (www.oldcastle.com). Each Subterra unit has fissures that allow water to pass through. Eco-Tek, meanwhile, is a solid unit that allows more or less water to pass around it, depending on how it is laid.

The pavers in Mr. George's driveway have 9 percent voids, while those in his front sidewalk are much smaller. The parking pad and drive cover about 800 square feet, and the sidewalk adds about 200 more. Mr. George said he paid $7,000 for the work, a substantial discount because Mr. Kreinbrook was still learning how to install it.

Mr. Welling said installation of Eco-Tek usually costs 10 percent to 20 percent more than traditional concrete pavers, partially because it often requires more excavation and a deeper base. Depending upon the subsoil's makeup, installation could cost up to 50 percent more, he said.

Mr. George said he didn't mind paying more because he believes Eco-Tek will hold up much longer than a concrete or asphalt driveway.

"Those are slabs, which move and crack. This is like a membrane. It flexes in every direction," he said.

Mr. George first worked with Eco-Tek when he specified it for an outdoor courtyard and main entry plaza at Powdermill Nature Reserve in Rector, Westmoreland County. He and his wife aren't afraid to use their house as a sort of laboratory for unique concepts and materials.

"We're always dreaming up projects," he said, laughing.