Location Agoura Hills, CA
Site 70 acres
Completed 2012 (Phase I)
Program Offices, conference center

When Conrad Hilton established the Conrad N. Hilton Foundation in 1944, the Hilton Hotels founder instructed the organization to “relieve the suffering, the distressed, and the destitute.” For more than 65 years, it’s done exactly that by providing grants to nonprofit organizations working to improve the lives of disadvantaged people around the world.

Today, the Hilton Foundation has expanded its ideology to help not only people, but also the planet. President and CEO Steven Hilton, Conrad’s grandson, made sustainability a major theme when the foundation decided to build a permanent home.

“The Hilton Foundation’s mission is to help the poorest of the poor,” explains Susan Van Atta, president of Van Atta Associates, the landscape architect chosen for the new Hilton Foundation headquarters. “So, it seemed appropriate to Steve that if you were to build a new office building, that you would do it in a way that’s sensitive to the environment and conserving of resources. It was his dream for the foundation to have its own office building, and for that building to be a reflection—directly or indirectly—of its values.”

A canvas ready for green.
The Hilton Foundation’s new building will soon boast two green roofs—the larger covers 3,400 square feet, while the smaller one, on the lower level, will be populated with stones and moss gathered from the building site.

Hilton’s dream became a reality when he acquired 61 acres at the base of the Santa Monica Mountains in Agoura Hills, California, approximately 30 minutes outside of Los Angeles. “The existing setting is really beautiful,” Van Atta says of the building’s site, which rests at the bottom of a foothill known as Ladyface Mountain. “Especially for someone like Steve Hilton, who loves the California native flora. There was a lot on the site from which to derive inspiration.”

But Hilton wasn’t the only one who found the site inspirational; the city did too. When it approved the Hilton Foundation headquarters in March 2011, the Agoura Hills City Council did so on the condition that the foundation replace 1,000 rare plants from the site at a 2-to-1 ratio. At that point it was clear: landscape architecture would be a huge part of the project’s design.


Landscape Architect Van Atta Associates
Client Conrad N. Hilton Foundation
Architect ZGF Architects
General Contractor Matt Construction

Enter Van Atta, whose seven-person firm has specialized in sustainable landscape design since its founding in 1985. In order to meet city requirements, Van Atta’s first focus was stabilizing and grading the slope, which allowed the city to safely widen the thoroughfare that provides access to the site. Second, unsurprisingly, was water management. Because one of the foundation’s strategic initiatives is to “increase sustainable access to safe water for people in severe need in developing countries,” the site of the new headquarters needed to serve as a model for sustainable water-use and storm-water design.

The landscape team chose a passive irrigation system that uses bioswales and rain gardens to capture, store, treat, and use all water that falls on the site. Assisting this process is a computer-monitored controller with low-volume irrigation heads, which will save up to a million gallons of water every year. Separately, roof runoff is captured in a subsurface Firestone EPIC System that irrigates the native turf area above it. Even the ornamental fountain is powered by rainwater. “Our overall approach to watershed management has to do with celebrating it and making it beautiful and obvious, as opposed to putting it in pipes and hiding it,” Van Atta says.

What Hilton did want to hide—or camouflage—was the building itself, in order to help the structure blend into its natural surroundings. The building uses glass and rock, and it has a low profile that hugs rather than obstructs the view of Ladyface Mountain.

“In an augmented way, it’s as though this building is tucked into a natural landscape,” says Van Atta, who designed two green roofs whose materials reflect the Santa Monica Mountains for the office building. The first green roof, which covers 570 square feet on the lower level, is composed of rocks and moss gathered on-site. The second, a more extensive system nearly six times the size of the first, uses pre-grown sedum trays to minimize the heat island effect and naturally cool the building below.


Certification LEED Platinum Plus (pending)
Site Slope stabilized to reduce erosion, oaks transplanted to strategic locations
Landscape Native plants include oaks, coastal sage, herb garden, and fruit trees
Water Rain gardens for natural filtration, cistern for rainwater capture, passive irrigation
Roof Dual native-plant green roofs total nearly 4,000 square feet
Renewable Energy Solar panels double as shade structures

The philosophy that drives the green roofs is evident throughout the site, which is lush with vegetation, including native grasses, coastal sage, chaparral species, and oaks. “We love oak woodlands here in California,” Van Atta says. “They’re a really attractive plant community. So, we’ve created a new oak woodland between the parking lot and the building. We’ve planted hundreds of new trees, which provide shade and some screening from the street.”

Old trees are just as important as new ones. Although many preexisting oaks had to be removed for construction, several were saved and placed conspicuously around the landscape. One, for instance, is in the center of a closed courtyard that’s used for special events. “The courtyard really celebrates that oak tree, which would have been lost if we hadn’t transplanted it,” Van Atta says.

Other features might not be as pretty as the oaks but serve important purposes: solar panels in the parking lot shade cars and help make the building net zero in terms of energy, and on the south side of the structure is an edible garden with fruit trees and herbs.

It’s a far cry from the foundation’s previous headquarters, which was a leased space in Century City. “They didn’t have anything to say about the landscape as people who leased their space,” Van Atta says. “Century City is very urban and car-dominated. Steve [Hilton] went out of his way to find a beautiful setting for an office building that was natural as opposed to urban. That’s unique.”

Hilton Foundation’s plan for growth is just as sustainable as its headquarters’ landscaping; the building completed in fall 2012 is only phase one of a four-phase project that will be constructed over the next 25 years.

“This new home in Agoura Hills will prepare the Hilton Foundation for the time it will double in size and staff,” reads a statement on the Hilton Foundation website. “My father, Barron Hilton, [85], has pledged his intent to follow in the footsteps of his father, Conrad Hilton, and contribute 97 percent of his entire net worth at the time of his passing. This new project will allow us to grow accordingly into the future.”