Energy Efficient Strategies
The campus includes a variety of energy efficiency strategies, like a roof-mounted solar energy system which provides energy for more than one-third of the hot water use. Below the surface is a 750,000 gallon thermal energy storage (TES) tank. This has several key positive impacts:
- Chiller plant capacity was reduced by about half from the peak loads, significantly reducing the chiller capital costs, space requirements and refrigerant charge. The TES tank absorbs the peak fluctuations in cooling demand without additional chiller capacity. The chiller cost savings went a long way towards paying for the tank itself.
- Air-cooled chillers could be used with no energy penalty compared to water-cooled chillers since they operate primarily at night during periods of low ambient temperatures. This saved about 2.6m gallons of water per year compared to water-cooled chillers.
- The ability to adapt the chilled water plant for future expansion or energy rate structure changes can be achieved by simply changing the operational strategy of the TES tank.
“A sustainable campus was a natural result of the foundation’s overall philosophy, keeping in line with values to be a good steward and positive addition to the neighborhood. We share this [LEED-NC Platinum] award with our many partners on the project – who all shared a common goal to build the right building for foundation staff to do their best work, while keeping an eye on mitigating impact to the local community.”
- Martha Choe, chief administrative officer for the Bill & Melinda Gates Foundation
In order to achieve the design team's rainwater harvesting goals, Arup's plumbing engineers, working with partner firms GGN and KPFF, had to verify how much irrigation water was needed for several acres of planting and how much evaporation was likely to occur from tens of thousands of square feet of water features. The result was a 940,000-gallon tank that’s the size of 1.5 Olympic-sized swimming pools. Located in the corner of the basement that didn’t have anything else programmed for the space, it saves the campus 2.5 million gallons of water each year.
Early in the schematic design stage, Arup's acousticians brought a portable SoundLab to the Foundation and NBBJ offices to demonstrate differing levels of speech privacy they could achieve with various wall partition constructions.
Identical prototype offices were mocked up from each manufacturer, and the Arup acoustics team took real sound recordings of the acoustic performance and speech privacy level that each provided. For this sound modelling exercise, NBBJ and key foundation stakeholders visited Arup’s permanent acoustically isolated SoundLab in San Francisco to listen to the difference.
The SoundLab helped the client and design team understand how a variety of design aspects impact the acoustic environment, which in turn influenced both comfort and productivity in the Foundation's offices.