Exploratorium’s new waterfront home dips into the Bay for radiant system
When it comes to celebrating the new Exploratorium museum project, located at Pier 15 along San Francisco’s Embarcadero, the engineering and systems design professionals at Integral Group tend to take it a bit … well, personally.
“From the outset, our client was determined that its new home be as sustainable as possible, so we knew the Exploratorium would be a perfect match with our own corporate commitment to green values,” says project manager Joseph Wenisch, who then adds that other factors have also spurred Integral’s enthusiasm for the project.
“While it is exciting and gratifying to work on a project that will leave a huge and lasting mark on the entire Bay area, the Exploratorium is also a very cool institution that occupies a prominent place in the cultural and educational life of San Francisco,” he continues, noting that the museum draws 500,000 visitors annually and another 26 million to its website. Attendance at the new site is estimated to exceed one million.
The Exploratorium’s current home at the Palace of Fine Arts in San Francisco’s Marina District was erected nearly a century ago for the 1915 Panama-Pacific International Exposition.
At the heart of San Francisco’s waterfront, the newly renovated facility at Pier 15 promises to offer a compelling contrast in terms of breathtaking vistas, visitor amenities, and an impressive assortment of architectural and engineering innovations. Built in 1931 and vacant for a number of years, the more than 800-ft-long pier has undergone a gut renovation, including major structural repairs to its pilings to make it earthquake-safe for the next century.
Slated for completion by the end of 2012, the massive construction project will yield approximately 330,000 sq ft of indoor and outdoor space. A new mezzanine level will house classrooms, conference areas, and offices. The finishing touch is an all-glass Observatory that anchors the back of the new complex at the end of the pier’s 800-ft projection into the bay.
All these upgrades and alterations were done within strict historical-preservation guidelines, with the idea of returning the building to its original look. As a consequence, certain architectural aspects, such as the façade and many of the windows, could be repaired and cleaned but were otherwise left unchanged. Some alterations, such as the addition of solar panels to the roof, won approval. Others, such as insulating the walls to prevent heat loss or gain, were disallowed.
“Historical preservation was a factor in virtually every design decision we made,” says Wenisch.
NET-ZERO AND LEED®GOLD GOALS
When the Exploratorium becomes fully operational in the spring of 2013, its goal is to become the largest net-zero energy museum in the United States, if not the world. True to the spirit of the Exploratorium — and the nature of net zero — achieving such an ambitious degree of energy efficiency will require monitoring and tinkering over time.
Targeting LEED® Gold certification, the new Exploratorium will have many notable green features, including solar power, a bay water radiant cooling system, a dedicated outside air system, and multifaceted water savings.
The building’s entire annual electrical consumption will be fully offset by a 1.3 megawatt-AC, PV solar-panel system erected on the rooftop of the Pier 15 structure.
Even without the photovoltaics, the renovated facility is projected to be 57% more efficient than the ASHRAE 90.1 baseline standard for a typical U.S. museum, thanks in part to its innovative use of water from the San Francisco Bay. Depending on the season, the latter will function as either a heat sink or a heat source for a radiant heating and cooling system that covers approximately 90% of the floor space.
The job of raising or lowering the temperature of that bay water to meet comfort demand will be handled by eight, 50-ton, water-to-water heat pumps, made by Multistack. These electric chilled heaters feed a four-pipe system that carries either hot or chilled water to a 200,000-ft network of crosslinked polyethylene (PEX) tubing. Made by Uponor Inc., the tubing is embedded in concrete slabs on two levels and spanning 82 different heating-cooling zones. Each zone has a control valve and a thermostat to switch between heating and cooling, whatever the need.
Bay water will be continuously pumped in and out of the building. First, it moves through low-pressure microscreen drum filters to sift particles larger than 30 microns. Then it circulates through an UV-ray sterilizer that keeps the system free from plant growth.
The filtered water is then transferred to a 4,000-gal concrete tank beneath the pier before moving to a pair of titanium heat exchangers. Each exchanger is designed to handle half the load during normal operations and two thirds during maintenance periods. Depending on the need for heating or chilled water, the bay water exchanges heat with the “condenser water” circulating on the opposite side of the titanium units. Variable-speed pumps then move the condenser water to the chiller heaters and to the tubing network embedded in the floors throughout the building. The bay water never moves beyond the heat exchangers. That’s because salt water would corrode the heat pumps and other mechanical components in just a few months.
Once the heat exchange process is complete, the bay water returns to its source —completely unchanged and with no chemical treatment, as stipulated by the local permitting authorities. All of the above is accomplished in a single space inside Pier 15, called the Bay Water Mechanical Room, whose operations will be available for viewing by museum visitors.
No other type of water-heating equipment is used in the building, nor is there any use of fossil fuels except for highly limited cooking purposes in a small restaurant — thus, the net-zero carbon designation.
SUCCESS THE SECOND TIME AROUND
The new Exploratorium is distinctive and even unique in many ways. But it is not the only renovated pier on The Embarcadero to employ radiant slab heating and cooling. Nor is it the first to attempt to save water and energy by using bay water with such a system.
Completed in 2001, the renovation of Pier 1 also employed these cutting-edge technologies. Unfortunately, while the building’s heating and cooling systems have continued to function properly, there were problems with the use of bay water at the outset.
“They ended up replacing the bay water system with a cooling tower,” says Wenisch, who also acknowledges that the Pier 1 situation “had an impact on the planning of the Pier 15 renovation a decade later. We had to fight through the negatives associated with that earlier project.”
But Integral believes that the bay water-driven radiant slab system at Pier 15 will avoid the problems of its counterpart a half-mile away down The Embarcadero, on its way to becoming “a great and long-lasting example of how to do green design.”