Net zero energy, LEED Platinum project raises the bar on eco-friendly office design.
For its new headquarters in Los Altos, California, the David and Lucile Packard Foundation put its building budget where its mouth is. The philanthropic organization, whose four program areas include conservation and science, asked San Francisco-based EHDD to design a net zero energy, LEED Platinum building that would serve as a model of cutting-edge green building techniques. “They wanted to achieve net zero in a way that was replicable, and that showed the path forward for others to follow,” said project manager Brad Jacobson. “It was not just a one-off thing, not just a showcase.” The building’s facade was fundamental to its success as an example of sustainable design. “We were surprised at how significant the envelope is, even in the most benign climate,” said Jacobson. “Pushing the envelope to really high performance made significant energy and comfort impacts, and could be justified even on a first-cost basis.”Deep overhangs, exterior movable blinds, shade trees, and balconies reduce solar gain along the building’s southwest elevation. (Jeremy Bittermann)
EHDD began by considering the building’s siting. Because the street grid in Los Altos is angled 40 degrees to the south, orienting to the street would result in a long southwest elevation. The architects asked daylighting consultants Loisos + Ubbelohde what penalty this would entail. “They said you have to keep all solar gain out of the southwest facade; if you do that, the energy penalty will be in the realm of less than five percent,” recalled Jacobson. “But you really have to do an excellent job on sunshading. That was our mission.” EHDD designed deep overhangs over much of the facade’s southwest face, and added balconies and shade trees for additional protection. Where the glazing remained exposed, they installed external movable blinds from Nysan that operate on an astronomic time clock. “The blinds worked really well,” said Jacobson. “We were surprised how easy they were to commission and get working, and how relatively robust they are.”
Thermal bridging was another area of concern for the architects. EHDD worked with Atelier Ten on thermal modeling of the wall, and discovered that any metal stud wall would sacrifice performance. They opted instead for wood stud construction, and switched to 24 on center framing to reduce thermal bridging through the framing structure. For insulation, the architects added one-inch external mineral wallboard from Roxul. On advice from structural engineers Tipping Mar, they installed FRP plates to separate external elements like balconies from the main structure.
Because of the building’s location, EHDD did not initially consider triple glazing for the Packard Foundation offices. “We wrote it off at first,” said Jacobson. “We thought, that can’t be cost effective in this climate.” But Integral Group’s energy analysis convinced the design team otherwise. The improvement in comfort allowed by triple element windows from Serious Materials (now Alpen HPP) was such that the architects were able to eliminate a planned perimeter heating system, resulting in an estimated savings of twice the cost of the glazing upgrade. “It’s a really good envelope,” said Jacobson. “We did heat sensor testing of the building, and you can really see that it’s working as it’s supposed to. You don’t see the studs, and the windows are not leaking a lot of heat, so that’s been a real success.”
The architects clad the building in local and sustainable materials, including FSC-certified western red cedar, stone sourced from within a 500-mile radius, and architectural copper. “Architectural copper is a really interesting material,” observed Jacobson. “It’s actually about 80-90 percent recycled because it’s valued. It doesn’t need refinishing and it patinas nicely. For a building being built to last 100 years, it has a good shot at never needing to be refinished or replaced.”
Jacobson summarizes his firm’s approach to the design of the Packard Foundation headquarters as “Passive House light.” “At the same time we were doing a Passive House for a climate science researcher we’d worked with in the past,” he said. “We were working on both and learning from each. It’s a different type of building, but a lot of the same principles apply: good air sealing, eliminating thermal bridging, and pushing the envelope further than you think makes sense.”Triple-element windows significantly improved comfort and resulted in a net first-cost savings. (David Duncan Livingston)