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Enjoy this blog from Dec. 19, 2014.

Shedd Aquarium’s magnificent octagonal skylight got a facelift this year. The cutting-edge project brought the 4,500-square-foot glass surface into the energy-efficient 21st century while preserving its historic Beaux-Arts appearance.

The roof of Shedd's rotunda featuring blue glass panels edged by wave motifs.

During the eight-month tear-out and installation, quarter-inch wire glass was replaced with inch-thick dual thermal-pane glazing set in insulating thermal-pane frames. The new glass keeps heat from escaping the building while reflecting solar radiation to reduce the “heat island effect” that can raise the city’s summer temperature. The new glass is more impact resistant (think hail) than standard glass, and it’s even sturdy enough to support the weight of four workmen.

Bob Wengel, Shedd’s vice president of facilities, oversaw this massive upgrade, which took from February until October. He had many considerations going into the project.

His first concern was the ongoing operation of the aquarium. “I could not shut the building down, even though we were taking the roof off section by section,” he says. To keep the elements out, as one-eighth of old skylight was removed, the opening was covered with temporary roofing made of 2-foot-by-4-foot plywood sheets laminated with a modified rubber roof membrane. Neither the guest experience nor the animal care was interrupted or impaired during the process.

He also had to decide on the best site for scaffolding to give workers access to the roof, between six and eight stories up. The structure took up a minimally intrusive footprint in the aquarium’s loading dock area.

Measurements for the new framing and glass had to be meticulous because the skylight was built in a shop near Milwaukee, transported to Shedd, erected in place and installed. Bob was determined to avoid the cost and intrusion of a crane for materials handling and heavy structural work, so everything was moved by way of the scaffolding.

A construction worker works on fastening new glass panels on the roof of Shedd's rotunda.

The old steel frame was replaced with a coated aluminum one, and then the precut panes of glass— 277 of them—were set by hand.

The new panes are longer, wider and 480 fewer than those in the old skylight, a change that had to be approved by the Landmarks Preservation Council of Illinois and the Chicago Plan Commission for compatibility with Shedd’s National Historic Landmark status and the Lakefront Protection Ordinance, respectively. Representatives of the groups reviewed a full-sized mockup of three glass panels as they would appear in daylight and at night.

The aquarium took pains to replicate the historic shingled look of the horizontal rows of glass by using wedge-shaped moldings. “If you look at pictures of the original skylight and the new one, it’s pretty darn close,” Bob says. The landmarks and lakefront reviewers agreed.

Glass color was another challenge because the skylight panes being replaced were not the originals.

“We didn’t have a color photo of the building from the 1930s,” Bob says, “but we made assumptions based on the time period of what color the glass might have been.” The result was a historically acceptable dark, vaguely green tint.

One of the biggest challenges was how to temporarily remove the rows of cresting waves that appear to roll up the hips of the dome to the trident-topped finial, giving the building so much visual energy. Each row of crests consists of five sections, weighing about 800 pounds apiece. The contractor, Berglund Construction, devised a contraption that lifted the lead crests out of place and suspended them over the work area, again eliminating the need for a crane.

“This thing showed up,” Bob says, “an aluminum framework with winches and bow cranks. They installed it and literally cranked up the crests.”

The machine enabled the workers to clean and treat the metal waves, which are about 10 inches high, clean and coat the I-beams supporting the crests, install flashing and sealants around the new skylight frame and lower the crests back into place. “The thing was awesome,” Bob says.

But there was more work to do than replacing the skylight. Two levels of flat roof over the rotunda received all-new covering, damaged interior bricks were replaced, deck concrete was repaired, and rotunda ventilation systems were updated.

A historic image of the roof of Shedd's rotunda, topped with Neptune's trident.
Scaffolding surrounds the roof of Shedd's rotunda.

If the skylight was an engineering feat, the repair or replacement of sections of the aquarium’s stunning terra-cotta ornamentation was an artistic one.

“A lot of the terra cotta was cracked, broken, or spalled,” says Bob. Like pottery, terra cotta is made of clay that is heavily glazed and fired. It’s a durable building material, but after 85 years of exposure on the lakefront, a number of pieces needed repair.

About 50 damaged sections had to be replaced, including some of the blocks of sea turtles and eels that go around the crown of the building. They were removed and patched enough to make molds. Then new pieces were cast in glass fiber reinforced concrete, or GFRC, by a company in New York. “It’s a way better product that holds up to the weather,” Bob says. The pieces came back a perfect match in color and finish.

In addition to being responsible for maintaining the facility and preserving the landmark status of the original building, Bob is Shedd’s champion of sustainable practices in the areas of energy, waste and water. “Our goal is to divert 80 percent of construction debris from landfills,” he says. “We probably diverted 85 percent on this job. There was very little that couldn’t be recycled.”

He is also constantly looking for better ways to lower Shedd’s energy use. In a recent energy-efficiency evaluation among six U.S. aquariums, Shedd came out on top.

“We had the lowest energy consumption and,” Bob points out, “we’re the oldest facility.” Shedd beat the benchmark for overall energy conservation by 15 percent, and with the new high-performance skylight, he estimates that Shedd’s energy usage now is 20 percent better than the standard set.

Bob didn’t have to wait long for visual proof that the new insulating glass panes are keeping the heat in and the cold out: He arrived at Shedd one December morning to see a fresh coating of snow on the dome, with no sign of melting, probably for the first time ever.

—Karen Furnweger, web editor

The rotunda renovation project was done thanks to generous support from the Public Museum Capital Grants Program from the Illinois Department of Natural Resources–Illinois State Museum.