Fully appreciating the marvelous new addition to the St. Louis Art Museum (SLAM) means appreciating the unseen.
The best museum buildings do nothing to distract attention away from the exhibits. In designing the St. Louis Art Museum’s new East Building, David Chipperfield Architects and HOK pushed materials to new limits and tested the ingenuity of engineers, project managers, and craftspeople to give a deeper and fuller meaning to the concept of a building without distractions.
Think about the typical features of a modern building: the fluorescent lights, light switches, security cameras, fire sprinklers systems, and voice and data systems. They’re in the art museum addition, but they’re invisible. Add in the special systems that an art museum needs to protect its treasures, such as glass break detectors and heaters to eliminate drafts and maintain constant temperatures. They’re there, but they’re invisible, too. There are no drafts, switches, or obtrusive lamps or cameras to distract from appreciation of art.
One of the most innovative features of the East Building is a coffered ceiling with 300 skylights. The ceiling lets natural light flood into the collection galleries and public spaces, giving visitors a dynamic viewing experience that changes as the light changes outdoors.
“In a typical project, you have a structure covered by studs and drywall, but in this case the structure was the finish. The ceiling structure was the finished ceiling, and it was concrete,” said Matthew Pfund, vice president, Tarlton Corporation, who directed the project. We were pushing materials way outside normal tolerances to satisfy the design intent It was really cool stuff if you love technical challenges in construction,” he said.
In almost any concrete garage or basement, thin cracks and “bug holes,” or air pockets and pits, are visible, but not in the East Building’s coffered ceiling. “The coffers are so smooth are really attractive,” said SLAM spokesman Matt Hathaway.
Breckenridge Material stepped up to develop the concrete mix that met the architects’ requirements for strength and a smooth, unpitted surface. “They needed a high viscosity paste that wouldn’t separate and would give them the finish they wanted,” said Jeffrey Whidden, senior vice president, Breckenridge Material Co. Most unusual for concrete, the architects’ esthetic requirements included crisp, g0-degree corners.
The architects had called for using self-consolidating concrete. “Probably less than three percent of the concrete used globally is self- consolidating concrete, and probably less than one-tenth of a percent is self-consolidating concrete used for architectural purposes, because it is hard to make and hard to make repeatedly,” Whidden said. “This is a rare use of the material.”
Breckenridge Material and the concrete contractor, McCarthy Building Company, went to extreme lengths to make sure they got a consistently smooth finish.
“We used 3/8-inch aggregate instead of 3/4-inch. We dedicated a plant to make just this, and we made sure that no truck carried more than one load of it, because we didn’t want it affected by residue in the truck. We used only clean trucks. And we had 10 practice pours with McCarthy, then two more on mock-ups, so that they could see how to do their forms to get a smooth finish. They were so careful they were vacuuming forms before each pour,” Whidden said.
“There is a tremendous amount above the coffers and in the concrete, and that is what was tough to do,” said Steve Briesacher, project manager for Guarantee Electrical Contractors.
Below the skylights, and above the coffers, are motorized horizontal shades that open in the daytime. On top of the coffers are 1300 fluorescent lights that shine up on the shades to reflect light down when there is not enough natural light. Within the coffers are 6g4 light spreaders with ultraviolet light filters to diffuse the light and protect the art. At the center of each light spreader is a vertically mounted extruded aluminum light track, from which hangs an incandescent light.
The museum’s curators can set foot-candle thresholds for each gallery to control the amount of light in each space separately with automated lighting controls. Working with photo sensors hidden in the ceiling, the lighting controls manage the shades and supplemental artificial lighting to illuminate the room as the curators want based on the amount of natural light coming through the skylights.
The coffer walls are only nine inches wide. Within that nine inches, “you have to get power for the incandescents in the spreaders, power for the shades, power for the fluorescents, voice and data systems, glass break detectors,andcameras,”Briesachersaid.”Patronscan’tseethem,butthey are all there. That is what was difficult to do.”
And those are just the electrical systems. They share room with a temperature control system and a fire sprinkler system. There are 417 600-watt heaters mounted below the glass to eliminate down drafts. Sprinkler heads for the fire protection system installed by Ahern Fire Protection are hidden in the diffusers.
“All the raceway systems and security systems are concealed within the concrete. That, and coordinating all the systems to look like nothing is there was the biggest challenge. It was a difficult task figuring out how to make it work, but we did it. We’re extremely proud that you don’t notice them,” Briesacher
The light spreaders, by the way, were made by a local metal fabricator, Troco, for half of what a European company was going to charge.
The heating, ventilating, and air conditioning (HVAC) system also had to be invisible, but air ducts would not fit behind the coffer walls. In addition, “Curators didn’t want vents in the walls, so we have an underfloor system,” Hathaway said. St. Louis-based William Tao & Associates worked closely with Chipperfield and his engineering consultant, Arup, to design a system that met their temperature, humidity, acoustic, and esthetic standards.
“It is almost a displacement type system,” said John Whitacre, the lead mechanical designer. Air is delivered at very low velocities through the floor and the return air vents are on the room edges at the top of the coffers.
Very low velocity air flow was a major issue, so you don’t feel air moving,” Whitacre said
Air handlers deliver air to the floor cavity at 65 degrees instead of the 55 degrees that is standard for an overhead system. “We want 65-degree air so that we don’t freeze people’s ankles,” he said. In order to get dehumidification, the cooler coil has to discharge air at 55 at degrees. That air then passes through a return air coil that warms it to 65 degrees. Doing that instead of prevent temperatures from fluctuating more than two degrees from the set temperature or the humidity from changing more than five percent are hidden from view.
The grills also offer access to hidden electrical power and data outlets for those exhibits that need power or data.
“The floor and grills are very, very strong,” Whitacre said. Flooring Systems, Inc., installed the floors.
The quest for invisibility even extended to parts of the doors. H&G/ Schultz Door supplied all of the interior and exterior doors for the new building.
“The most important things are what you don’t see,” said President & CEO Jay Manzo. “The 16-foot sliding doors, which weigh 1,000 pounds each, needed custom- made, heavy-duty tracks installed in the concrete. When you pour the concrete, you are done. You can’t cut or adjust the track after that. It has to be right. You don’t see that.
On the front entrance doors, you don’t see the automatic door closers buried in the concrete. When they are installed, they have to swing properly once the concrete is poured, because you can’t change them after that. “What you see are great esthetics. What you don’t see is all the engineering that went into the project behind the scenes,” he said.
The behind-the-scenes effort was exceptional. “The planning on this job was unlike any other I’ve been involved with,” said Pfund.
In Tarlton’s yard, they erected a big mock-up of the interior of the East
Building, turned to the same orientation as the museum so that it got the same light direction, then outfitted with the same skylights and motorized shades so that they could test light levels to make sure that the design was optimal for art work.
“We wanted to prove the design before we built it for the museum,” Pfund said. In addition to testing light levels, they poured sections of concrete and lifted them with a crane to see what they would look like. They also worried about wear from special events. They even poured red wine on floors and concrete surfaces and then cleaned it up to see if it would stain.
“We planned out everything and built mock-ups so the owner could see what Pfund said. The only exceptions to the mock-ups were the structural, mechanical, electrical, and plumbing systems, which were done in a 3-D building information model.
“It was a very unique project, the kind that only happens once or twice in a lifetime,” Manzo said.