Wenisch says radiant heating and cooling was an appropriate choice because of the building’s open spaces and the system’s energy efficiency. Traditionally, a radiant system is connected to a chiller with a cooling tower, but historic-preservation requirements at the pier and local mandates about maintaining access to public walkways precluded a cooling tower’s construction. In addition, the traditional way to heat buildings in San Francisco is with gas-fired boilers. Because of net-zero carbon goals, the team analyzed other options and discovered water-to-water heat pumps offered a good alternative with quick payback.
Wenisch says 100 percent free waterside cooling can be achieved for at least six months of the year because the bay is at an optimal temperature and the water can bypass the heat pumps. When more cooling is necessary, the heat pumps lower the temperature of the building’s chilled water, and the bay acts as a heat sink. During winter, the bay water is around 50 F and is used as a heat source for the heat pumps. “In winter, instead of using boilers, we’re using compressors run backward to make hot water,” Wenisch says. “It’s still low-temperature hot water—100 F— compared to the typical 180 F—that allows the heat pumps to operate very efficiently.”
To maintain the Exploratorium’s participatory pedagogy, the design team placed the building’s bay-water-related equipment in one room, creating an exhibit. “It’s so exciting that we can learn from our own space and share those lessons with others,” Bartels says.
The main exhibit spaces—90 percent of the building—feature a dedicated outdoor air system; there is no return-air ductwork in these spaces, which maintains good indoor air quality. (Spaces with higher occupancy have return air to help control humidity generated by people.) “Because we’re using radiant rather than using air to do the main heating and cooling, the code requirement for ventilation air is quite low so the air handlers are smaller than a standard air handler for a traditional HVAC system and we didn’t need nearly as much ductwork,” Wenisch notes. Air is relieved passively through louvers and historical vents at the clerestory roof.
Precious Spirit
Although the Exploratorium’s initial opening in 1969 produced little fanfare, there was much anticipation for its reopening in April 2013 in Pier 15. Would the new space be true to the museum’s philosophy? Would it also be faithful to San Francisco’s rich waterfront history? The answer, Bartels says, is yes. “There was a worry in the community that we would somehow change the soul of the Exploratorium,” he says. “But people immediately saw it was still the Exploratorium, just brought to the pier and expanded. That was the architects and construction folks paying attention to details. Everybody was together in wanting to keep the precious spirit we had developed in the palace intact.”
Although this wasn’t a project about making a splashy design statement, L’Italien feels strongly about maintaining San Francisco’s history and is pleased the community feels the same. “Many people who look at the pier will not see the nuance and will see it as it always was. We wanted to be sure we froze it in time; this is what the pier looked like at the dawn of the 21st century but also how it lived through most of the 20th century. It has battle wounds and blemishes that we felt were important to share. It might not have been an appropriate solution for all clients but we really felt it was for the Exploratorium. I’m really happy to say people who were the biggest naysayers said we really nailed it. That to me is what is ultimately most important: This is still the Exploratorium just in a very different place.”