A respected Los Angeles contractor for more than 30 years, Mehran Taslimi knows all the major architects in the city. But when he and his wife, Laila, set out to redesign their Tudor Revival house in Santa Monica, they were drawn to the sensibility of an underdog—Fleetwood Fernandez Architects, the small, local husband-and-wife design firm of Hunter Fleetwood and Paz Fernandez. “I thought I’d get their attention,” Taslimi says. “And I did.”

“They wanted something connected to the landscape,” explains Fleetwood, who, with Fernandez, drew up a series of innovative plans for the residence where the Taslimis had lived for nearly 20 years. Mehran knew he wanted the highest possible rating from the U.S. Green Building Council “and knew what that meant,” Fernandez says of her client’s commitment to the process it would entail. “It’s actually very hard.” When the designers struggled to adapt the cloistered old residence—derivative of a medieval style and a blustery climate—to their 21st-century vision, the Taslimis opted to start from scratch.

The new house is a striking 5,600-square-foot home that gracefully integrates with the site. On the front facade, an ipe-wood box sits lightly on a concrete plinth. Vertical wood fins wrap and peel away from second-floor windows, alleviating the solidity of the volume. Although the floor plan is long and linear, the rooms within are “layered and unveil themselves sequentially, while continuously engaging the landscape,” Fernandez says.

The most dramatic space in the house is the enormous living room. Here, the couple—philanthropists, patrons of the arts, and members of a large extended family—entertain as well as dine together, read, and just hang out. Glazed floor-to-ceiling walls, 33 feet wide by 10 feet high, slide into pockets, exposing the entire length of the room to the garden and the gentle weather of Santa Monica. A breeze circulates, a sycamore leaf skitters in, and the interior suddenly feels at one with the outdoors. “I’ve never been here when the entire house hasn’t been opened up,” Fernandez says.

A natural palette and simple expressions of materials prevail. Board-formed concrete makes up the southern wall, and the narrow, horizontal lines—neither too textured nor too polished—“are meant to be expressive of movement through the house,” Fleetwood says. (“When we moved in, it smelled like cedar”—the species used to support the concrete during casting—“for months,” Mehran recalls.) Terrazzo floors continue out to the patio; walnut cabinets are built-in; and oxidized maple veneer clads some interior walls in a hue (fine-tuned multiple times) that takes its cues from the concrete. “I feel like the whole house is tactile,” Fernandez says, noting the intentionally raw materials that enhance the effect. “None of the wood is finished. The concrete is barely sealed, the walnut isn’t sealed, and neither is the ipe. We were really interested in the idea of the house developing its own patina and changing, weathering.”

Glazed walls on the west facade open the kitchen to an outdoor dining area and, on the second floor, allow the master bedroom views of a roof garden on the garage—an especially delightful vista when California poppies are in bloom. Open to the sky, a stone-and-glass light well links the bedroom to the bathing area, ensuring privacy while ushering in ample light and fresh air. “The first time Laila took a bath, she said she was so moved by the experience,” Fernandez says. “She never imagined she could see the sky and the moon [from the tub], and was blown away.”

The designers also created the interiors, blending new and midcentury furnishings—a Nelson marshmallow sofa, nesting tables by Josef Albers—with custom pieces of their own, including the bed and side tables, which were “designed as an extension of the house: understated, functional, and focused on material integrity,” Fernandez says. Reflecting Laila’s passion for vintage lighting, a rare Gae Aulenti lamp with a mesh wrap throws dazzling shadows after dark.

“There are basically two houses,” Mehran says of the structure’s dramatic shifts from morning to night. “There’s a nighttime house and a daytime house, and they’re very different.” Contemporary art by Luisa Lambri, John Divola, and Ann Veronica Janssens, among others, mix with rare 19th-century Persian artwork from Mehran’s native Iran.

Two guest suites are upstairs, and there’s a basement below that contains living spaces as well as the mission control center for green systems such as water filtration and low-voltage controls. The Taslimis’ approach to sustainability was so rigorous, it even exposed a glitch in the LEED system: The house eschews air-conditioning; instead, the builders tunneled an earth tube beneath the house, importing outside air and reducing summer swelter by single-digit degrees. Despite the apparent ecological benefits that resulted, the team failed to earn points for these efforts. “LEED is built around the fact that people will [air] condition their homes,” says Fleetwood. “It’s a flaw, and [the organization] acknowledges that now.” Regardless, the designers were able to double up their tallies elsewhere in pursuit of certification.

“From the second you start demolition, everything counts,” Fernandez says of the LEED guidelines. In fact, 90 percent of the materials of the original house were diverted from landfills (Santa Monica requires only 70 percent). GSLA Landscape Architecture Studio elegantly designed a lush garden strictly with indigenous plants, a move that tipped the home over to LEED Platinum level with a point or two to spare.

Respecting the environment is “truly a lifestyle” for the Taslimis, Fernandez says, noting that her eco-friendly clients went so far as to avoid leather in the house, save for a single white Barcelona chair in the master bathroom. “It’s not just about achieving platinum level,” she adds. “They really live by it.”