The West Conservatory greenhouse is the centerpiece of the $250 million Longwood Reimagined project, the most ambitious progression ever made to the century-old garden. Photo courtesy of Longwood Gardens/Bill Hill
The team is scheduled to open the turf on November 22 by installing the plants and commissioning the numerous construction systems. Photo via Daniel Traub
In 1998, six marketing firms operating in other parts of the United States began meeting every six months to break up the most productive practices. No one could have predicted that a quarter of a century later, the group, called PeerCon, would go beyond its original foundation. purpose and directly enable the $250 million Longwood Reimagined Project, an ambitious 17-acre redevelopment in the center of historic Longwood Gardens near Wilmington, Delaware.
Fast forward 20 years to a 2018 PeerCon assembly in Seattle, attended by Greg Sawka, president and CEO of Bancroft Construction Co. , an original member of the organization and Longwood’s director of construction. At the time of the assembly, Sawka was making pre-construction plans for the task in Kennett Square, Pennsylvania. ItArray is undoubtedly the company’s most vital and sensitive project.
The biggest challenge to solve is the 32,000-square-foot West Conservatory, a metal greenhouse designed through WEISS/MANFREDI Architecture. The Longwood Reimagined icon, scheduled to open Nov. 22, features a subtly asymmetrical pleated roof with doubly curved elements, few repeats and tight tolerances.
The project, more confusing across a lawn that would be open to public construction, includes seven main internal and external parts, adding a total of 190,000 square feet divided into five different construction types and interconnected through concrete tunnels to a common power plant in the basement. under the greenhouse.
The expanding program was so multifaceted that Sawka Concept Bancroft needed help. Then, in Seattle, breaking with PeerCon tradition, he floated the idea of teaming up with another original member, GH Phipps Construction Cos.
Two years have passed. COVID-19 hit and work slowed down a bit for Phipps. Veteran Superintendent Bruce Schneider, who had been with Phipps since 1977, not only hired him for a task, but he was also lured by a swan song at the peak of his career earlier. retire. And he delighted to run in the botanical gardens.
“The stars aligned,” says Sawka. Instead of fully partnering, Bancroft and Phipps signed a loan agreement with Schneider in March 2021, when the structure began in Longwood.
The agreement “represented an important step forward for our peer organization,” says Schneider, Longwood’s chief superintendent. “I would also do it with our counterpart partner organizations. “
The 17-acre Longwood Reimagined progression along Crystalline Ridge expands the lawn crowd west of the centennial East Conservatory. Rendered courtesy of WEISS/MANFREDI with Reed Hilderbrand
Schneider passed on his new knowledge to Phipps, whether it was how to manage a larger team on a large-scale task and how Bancroft prepares the drawings. He was so inspired by the assignment that he temporarily informed his nephew, Mike Guillan, a 20-year Phipps Veteran, to sign up for him as one of the 4 superintendents of the assignment. The uncle and nephew live in a space in Longwood Gardens on campus and walk to work.
Schneider called the task “challenging and fabulous” and called it a “spectacular job” to finish a career. These feelings are shared through other team members, who describe it as an inspiring, challenging, collaborative and collegial opportunity.
The West Conservatory is a “work of art,” says Michael Lopuszanski, senior assignment manager for GMI Contractors, for the greenhouse construction.
Lopuszanski and others can thank Paul B. Redman, the garden’s president and CEO since 2006, for the opportunity to be galvanized. For the mastermind of Longwood Reimagined, the task is the realization of a vision to “document the afterlife and look to the future” of the 1,100-acre garden, which dates to 1921, and further delight the 1. 6 million annual garden visitors.
Redman set the tone for the task as a collaboration of all parties involved, garden management, horticulture staff, and the nearby community.
“The partnership between Longwood and Bancroft is extraordinary, and that’s not the case in this industry,” says Sawka, who led Bancroft for 10 of his 25 years in the role and has been involved in many of Longwood’s nearly 50 jobs. since 2007. “This [project] can be a style of doing things well,” he says.
The many curves of the greenhouse were across the curves of the Lord and Burnham greenhouses that once occupied the site. Photo courtesy of GMI contractors
Sawka recalled the appointment with his client this spring. It was Friday, around 6 p. m. , after a torrential downpour on the East Coast. Sawka out of town. His phone rang. It was Redman, who rarely called.
“I don’t forget to think, ‘Uh-oh,'” Sawka said, worried there was something in the place. Redman temporarily allayed his fears. He had called to say that as he drove past the rear into Longwood after the storm, he saw Tony Ingram, Bancroft’s senior director of appropriations, alone, shoveling dust on the road. “Paul’s message was, ‘We’ve got a smart one in Tony,'” Sawka says. “I already knew that, but it was smart to listen to it. “
For Longwood Reimagined, which Sawka says is on time and on budget despite schedule fixes caused primarily by COVID-19 and source chain issues, Bancroft is acting as structure-at-risk manager, with guaranteed maximum value of $226. 3 million.
The redevelopment is funded through $200 million from tax-exempt bond sales, $10 million in donation expenses and a $40 million donation from the Longwood Foundation, the personal foundation created through the garden’s creator, Pierre S. du Pont, for the operations of the nonprofit educational institution.
The well-known Lord and Burnham greenhouses and adjacent car park have become the crest for the new West Conservatory. Photo courtesy of Bancroft Construction
Longwood, Bancroft, and the design team began working together on the expansion in 2017. Formal quarterly meetings from 2018 to 2022 helped build “a culture of continuous improvement in our processes, communications, and problem-solving,” Ingram says.
Longwood Reimagined, which includes a reshuffling of the flow of guests, spreads the public west of the century-old East Conservatory along Crystalline Ridge, which overlooks the famous fountains to the south.
The main pieces of the project, with the exception of the box of 128 geothermal wells just to the south, are located along the ridge: the greenhouse, with its 232 to 141 feet above ground, replaces the displaced greenhouses. The tiny Cascade Garden is a new 3,800-square-foot greenhouse that retains the only existing design in North America by famed Brazilian landscape architect Roberto Burle Marx. Other key elements include an administrative and educational building called the Grove, a new dining place and event area at the foot of the East Conservatory overlooking the main fountain, a bonsai courtyard, and a tiered water lily.
The other heights of the pleated roofline offer the guest the feeling of being in a cathedral, under the highest peak, or a more intimate delight on the sides. Photo courtesy of GMI Contractors
For the glasshouse architecture, “we were inspired by the cathedral effect created by Longwood’s groves of trees and the curved geometries of the Lord and Burnham greenhouses that were previously on the site,” says Marion Weiss, a WEISS/MANFREDI partner. The lines of trees in the grove are “continued” into the glasshouse by lines of structural steel tree columns with curved limbs.
WEISS/MANFREDI designed a more intimate guest experience along the two long sides of the conservatory, where the gabled roof is lower, and a more exalted experience through the long middle segment, which tops out at 48. 5 feet. Five longitudinal roof elements, called gutters, are curved to half their length, either in plan, in segment, or both, to create the image of an even longer building, Weiss explains.
The “Greenhouse’s Mediterranean Garden celebrates Longwood’s cultivated gardens and wild landscapes,” explained through water, stones, and plants, says Kristin Frederickson, principal of landscape architect Reed Hilderbrand. To reflect this, the West Conservatory features indoor pools to create a floating building effect.
The structural engineer’s task was to lengthen and detail the expressed design so that “it was barely there,” says Jay Taylor, a retired senior director at Magnusson Klemencic Associates (MKA). This was not easy to do, because “it was not obvious how to translate architecture into a structural solution,” he adds.
Taylor knew that a popular solution would not work. In search of inspiration, he animated through two previous MKA projects in Seattle with highly incorporated and expressive metal and glass structures: Amazonian Spheres and the Olympic Sculpture Park Pavilion.
MKA spent from April 2018, when the concept was defined, to December 2019, fine-tuning the details, working with turnkey design greenhouse supplier, Roschmann Steel and Glass Construction, in Germany. “It takes a lot of work to make it look simple,” Taylor says.
For the glazed roof, the framework is composed of thirteen rows of wooden columns in the short direction and secondary metal in the long direction, resting on a single-level reinforced concrete base. The trunks are composed of two widths. flanged elements (WF), one for each member. At other heights, the trunk WFs are divided into two asymmetrical, taut and curved limbs, regularly hooked at their ends.
Concept graphic courtesy of MKA*Click on the symbol for more details
WEISS/MANFREDI has established a constant radius for curved branches, but each tree reads because the elastic characteristics of the branches differ, causing the trunk heights to be different, Taylor says.
Hollow structural tubes, called purlins, and curved shaped plate gutters are enlarged longitudinally between the frames of a traditional glass roof and the trees. X-shaped tension bars hold the frames laterally.
The design and alignment of each tree column and roof metal is imperative to ensure the giant skylight’s operable windows fit perfectly on top. Photo courtesy of GMI Contractors
The construction is symmetrical with respect to the central transverse axis, at the point on line seven of the 13th, but there is no axis of symmetry in the longitudinal direction. This set is metallic, explains GMI’s Lopuszanski.
Belt-to-frame and channel-to-frame connections have intentional openings for conduit. This allowed the conduit to sit on top of the metal elements, invisible from the ground, as the architect desired. “It’s rare for a structural connection to be designed and detailed based on the length of the electrical conduits,” says Hannah Bonotto, an associate at MKA.
For the greenhouse infrastructure, WEISS/MANFREDI specified passive and herbal heating, cooling and ventilation to minimize operational carbon emissions. Greenhouses are “inherently unsustainable,” says Michael Manfredi, spouse of WEISS/MANFREDI.
Even without a greenhouse, “it’s difficult to create a microclimate for both visitors and plants,” says Scott Frank, co-director of mechanical, electrical and plumbing engineer Jaros Baum.
Using the style to simulate herbal ventilation scenarios, the team was able to choose tolerable situations for the plantations and visitors. The result is “a design that will have particularly environmental and energy functionality compared to a traditional approach,” says Frank.
Nico Kienzl, founding director of Atelier Ten’s New York office, says that “passive methods must prevail,” there is perimeter heating and fans, especially to minimize fogging of windows in winter.
All formulas are incorporated using construction controls. For radiant heating and cooling, tubes are incorporated into the walkways. A horizontal formula of buried earth tubes directs ventilation air to the walkways, taking advantage of the constant temperature of the soil. During extreme weather conditions, additional heating and cooling coils in air treatment assemblies further refine the air temperature.
Unique heating of the root zone for plantings, including hydronic tubes, helps to maintain desired temperatures.
A geothermal energy formula and electric water-to-water heat pumps supply hot and cold water. In winter, heat is drawn from geowells in the ground to supply low-temperature hot water for warmth. In contrast, in summer, cooling is achieved by transferring heat from buildings to the ground.
For natural ventilation, the façade features automatically operated windows, located near the floor or near the tops of the roof. A steam piping snowmelt formula is incorporated into the design of the windows and mullions.
Bancroft sequenced the paintings to balance the desires of lawn operations and visitors. Although the projects had other start dates, they overlapped. Preparatory paintings for the West Conservatory will begin in March 2021. The demolition of the old grove was delayed until excavations were necessary at the West Conservatory. Work then begins on the restaurant and event space, followed by the new Cascade Garden and Waterlily Court.
There were many challenging situations early on, plus the wonder of having to upgrade the existing greenhouse’s main steam source before starting on the giant greenhouse. The team accelerated the update.
Finishing the paintings at height, such as installing ductwork and other pipes on the roof members of the giant greenhouse, was tricky because it was done from elevators situated at heights of 20 to 50 feet above the slab. Bancroft ordered that the ceiling paintings begin as soon as crews finished installing a bay of metal and glass, before cleaning the slab for waterproofing. “This required making plans for the number of elevators that could run in each structural bay and the series of trades that run east to west between glass and metal,” says Bancroft’s Ingram.
Once completed, the elevators were removed and other work began on top of the structural slab, adding waterproofing and installing the prefabricated walkways that delimit the indoor pools, four feet above the structural slab. The crews then carried out the final aerial tasks. from the elevators to the walkways, in preparation for interior landscaping.
Even the 17-acre structure site, which includes six gardens with pavers, drains and more, as well as extensive landscaping around the structures, were not easy to coordinate. The landscaping schedule, logistics, and effects on the structure were all factored into the design. it planned discussions and required closer-than-usual coordination between domestic and foreign trade, Ingram says. The co-positioning of business partners has helped facilitate this, he adds.
Graphic courtesy of WEISS/MANFREDI
A major challenge was the delay in the delivery of electrical switchgear, ordered based on the announced delivery time of 56 weeks. The Bancroft team was able to work directly with its business partners and suppliers to reduce the supplier’s revised 86-week delivery estimate to approximately 15 weeks. Permanent power had to be available in time for the start-up of critical equipment, adding chillers and air handling units. This made it imaginable to begin completing the paintings.
By wonderful chance, the lawn and assignment team had to close their doors for 4 days, starting on September 4th, because an inmate escaped and hid in the area. Bancroft and Longwood were able to coordinate with local and state authorities to access the site. for the essential watering necessary for newly planted landscapes.
A bigger challenge was that the cooler scheduled to start was prepared for the week of closure. In anticipation, the supplier’s representative had come from out of town. To allow the start, start as planned and avoid a After two months of delay, the police escorted a small team to the site.
The Western Conservatory is the most confusing task. To begin with, “the production required an enormous effort,” says Marco Bürner, commissioning director at Roschmann, who signed a turnkey contract for the building worth $27. 1 million.
The war between Russia and Ukraine has confused both the production and shipment of the glass, which is manufactured near the Russian border. For protection reasons, the design team did not leave the factory. They had to settle for virtual meetings.
One of the many demanding production situations makes each of the approximately 1,400 roof panels unique, says Bürner. Two visual models and a functional model were used to expand the glazing system, all of which were manufactured in Germany. It would be best to make the mock-up of the functions in a control facility in York, Pennsylvania, to be closer to the design team.
Metal fabrication is also a challenge, especially due to the curved elements. Connections from curved elements to direct WF elements are taken into account.
“The metal profile bends so much that it warps,” says Bürner, adding that the team had been alerted to the option, but “was surprised that it happened at this point and at each and every connection. “
MKA’s Bonotto explains: “When you bend a limb, you take on a dimension. » The WF is elongated on one side, which is tightened, and compressed on the other.
Structural slab waterproofing, comprising water basins, irrigation systems and more, essential to protect the central application plant in the basement. Photo courtesy of the Roschmann Group
Bonotto and other members of the structure team traveled to the manufacturer’s factory in Germany to find an alternative solution. The solution is to notch the ends of the bent members and then fill them with welded metal. This way the ends of the curved elements would fit into the direct elements. The filled notches were then filled so that they were flush with the direct beam and not visible at all in the expressed metal structure.
Shipping congestion and the COVID pandemic have affected metal deliveries. There were no boxes available, the ports were overcrowded and there were huge queues, says Bürner.
An alternative solution was to use rolling trays instead of containers. Another was to replace the ports. ” We replace ports many times at both ends and use 3 ports in Europe and almost every port on the east coast,” says Bürner.
Working at Longwood was also a challenge. There was almost no learning curve during editing because there were few repetitions, says GMI’s Lopuszanski, a Roschmann replacement. Each row of columns was different because the trees are not arranged in a normal grid. The solder on the case has been adjusted, which is tricky. And the thousands of parts had to be perfectly compatible in 1/16 combination,” he adds.
Without teamwork, it would have been highly unlikely that the greenhouse could have been built; Total station that examines each and every component and their subsequent assembly and installation; and a virtual dual to locate piece by piece in the puzzle. “We built this using more of a three-dimensional style than drawings,” says Lopuszanski.
The assembly of the metal structure was carried out using a modified rod structure method. In preparation, blacksmiths welded a joint, usually composed of a shaft and its pinion, onto laser-level metal tables at waist height, before tilting the joint and reducing it into position with a crane.
Blacksmiths built the north-south moment frames in 4 sections. The goal was to move from east to west, but the bent metal in the center didn’t arrive in time, so the installer, Roma Steel, jumped to the west side. There were considerations about the game, but midfield members “came right in,” Lopuszanski said.
The meeting was ordered to begin at the row of columns on the north side, furthest from the crane to the south, which had a 4-column span. This allowed the other crews to paint “without being near the crane,” says Steve Hardeski. , general foreman of Roma Steel. The next line of columns started in the south and moved north, from north to south and so on.
Tensioners and other transient metals stabilized the frames and kept the shafts plumb until the secondary metal blocked everything and made the design self-supporting. “There was the same amount of welds on the floor,” Hardeski says.
The highest peak had its own tree. We had to attach the gable” to the two trees already installed in the pipe, explains Hardeski. To make the highest section compatible, blacksmiths had to use clamps, wedges and connecting bars, he adds.
The steel paint job began in late June 2022 and was finished in late October, more or less as planned, Lopuszanski says.
Currently, the completion of the work, the addition of plants, the filling of the pools and the commissioning of all the systems is underway or will begin soon. “We’re in the home stretch,” says Redman of Longwood. The transformation is meant to serve as a style for other Americans. gardens, he adds, but “if others are encouraged to expand or expand, that would be wonderful. “
Nadine M. Post, ENR’s Buildings Editor-at-Large, is an award-winning journalist with forty-five years of experience covering trends, issues, innovations, controversies and ambitious projects. The Post has written about many industry giants, adding up to 10 ENR winners. And it has covered disasters, failures and attacks, adding the 1993 bombing and the destruction of the World Trade Center in 2001. Project stories come with the remodeling of the World Trade Center; the Burj Khalifa, 828 meters high; Disney Concert Hall in Los Angeles; and the Bullitt Center and Rainier Square Tower in Seattle. In 1985, Post wrote McGraw-Hill’s e-book Restoring the Statue of Liberty (1986) for restoration architects Richard S. Hayden and Thierry W. Despont.
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