The lakeshore campus of Loyola University in Chicago is packed with buildings, much like the surrounding neighborhoods. Most universities guard carefully their available vast green spaces and open malls, and Loyola is no different. But in the third largest city in the United States, as in many dense urban areas, universities are sometimes forced to make tradeoffs in an effort to accommodate growing student populations.

As part of Loyola’s $500 million expansion program, a new 70,000-square-foot digital library was envisioned. It would link to the existing Cudahy Library and fit into one of the only available open spaces on Loyola’s campus — a small, open lawn tucked behind a dormitory on the shore of Lake Michigan. As part of the long-term plan, the adjacent dormitory would later be demolished to create a new quad unifying the east end of the 65-acre campus.

Building on a rare open space along the lake might seem counterintuitive, but the design team, led by Chicago architect Solomon Cordwell Buenz (SCB), saw an opportunity in this challenge. The key would be transparency — create an open building that allowed students in the library and on the future East Quad to visually connect to the precious lake. While the second, and equally important, focus would be efficiency, the building’s transparency couldn’t sacrifice the university’s high standards for an energy-efficient and cost-effective building that met its long-term goals.

The now complete Richard J. Klarchek Information Commons has proven a success on both fronts. Achieving a LEED Silver rating while keeping the cost below $22 million, the new library has now been open for longer than a year and has been well received by the university for its low energy use, which is nearly 50 percent less than the minimum requirements outlined by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). And the students have been just as responsive to the open, flexible use of the 24-7 facility — even occasionally getting there early to watch the sunrise through the building’s nearly panoramic view of Lake Michigan.

Collaboration for sustainability and transparency
To achieve this vision for transparency and aggressive energy efficiency, the SCB-led team worked together to integrate and optimize many systems in this state-of-the art jewel. Based on a detailed site analysis by climate engineer Transsolar (which included factors such as year-round temperatures, wind speed, and solar radiation), the team developed an energy solution including passive control, natural ventilation, and radiant heating and cooling.

The exterior of the double-skinned, west-facing window wall on the information commons is two-way, cable net glass. this component ensures the building’s transparency and views of Lake Michigan from the campus’s east quad — a key objective for Loyola university. Mark Beane/Loyola University Chicago

Many building components play a part in this effort for energy efficiency: the west-facing, double-skin glass façade system (a first in Chicago), the east façade’s operable windows facing the lake, shading devices, the under-floor air distribution (UFAD) system, and even the structure. A loop of radiant PEX tubes cast in the exposed barrel vault floor structure serves to heat and cool the space radiantly.

Building operation — The building operates in four modes depending upon the time of year and weather.

Natural mode occurs approximately 52 days per year. On moderately cool days (50˚F-68˚F) with low humidity, the east windows open to allow in fresh air, where it travels along the precast concrete ceiling to cool the space without drafty conditions. The air is pulled out through the west double-skin wall cavity and naturally exhausted out the top due to the vertical pressure differential created.

©Solomon Cordwell Buenz and James Steinkamp, Steinkamp Photography The radiant precast concrete floor system — a first in chicago — achieves the energy efficiency and long-term lifecycle project goals for Loyola university.

Hybrid mode occurs approximately 62 days per year. On slightly warmer days (68˚F-75˚F), the natural mode is augmented by circulating unconditioned (60˚F-68˚F) water from the university’s chilled water plant through the radiant floor/ceiling structure tubing, cooling spaces via the vault ceiling over time and using just 1/20 of the energy of a traditional forced air system.

Cooling mode occurs approximately 50 days per year. On Chicago’s hot, humid summer days (75˚F-95˚F), the east windows close while the west wall continues to exhaust warm air. The radiant structure cooling system is augmented by the UFAD system with displacement ventilation.

Heating mode occurs approximately 202 days per year. Most of the year, the temperature is cool enough (lower than 50˚F) to require heating. Hot water from the building’s boiler system is pumped through the radiant structure tubing, heating up the ceiling slabs while the UFAD system gradually delivers warm air, see Figure 1.

Figure 1: Structural engineers at Halvorson and Partners collaborated closely with all other design team members to integrate the structure with the other building systems. the building operates in three modes during the year: heating (55 percent), cooling (15 percent), and natural ventilation (30 percent). the system is designed to use 43 percent less energy than ASHrAe 90.1 – 2004 minimum requirements, and ongoing monitoring confirms energy savings are actually greater than anticipated. ©Solomon Cordwell Buenz

All of the building systems are controlled to transition automatically based on input from the roof-top weather station. In addition, during all modes, the automatic blinds on both facades are controlled based on the sun’s movements and intensities. Low-iron, argon-filled glass was used on both curtain walls for further energy efficiency.

The vision of transparency was always maintained in balance with the priority of energy efficiency. The open curtain walls on the east and west façades provide the first obvious gesture, and their careful design to be energy efficient and integral in the building’s energy systems ensured their viability. The curtain walls’ structures, including the west wall’s cable-stayed system and their supports, were carefully detailed to keep all elements to a minimum size

Everything between the two curtain walls was as minimal as possible, as well. Architecturally, the open plan was designed to achieve this goal. And structurally, the thinnest profiled structure possible was developed to be visually exposed and allow maximum clear views thought the building to the lake. The same holds true for the secondary structures, such as for the pair of feature stairs at the building entry.

Structural design story
Upon completion, the four-story structure integrates various systems and components for optimal efficiency of both cost and energy. The floor structure combines specialty precast concrete barrel vault slabs and ordinary precast concrete plank slabs supported by cast-in-place post-tensioned girders. These are supported by interior cast-in-place concrete columns and architectural precast concrete exterior walls, which double as structural shear walls for the lateral load resisting system. In addition to this primary structure, a double-skinned glass wall on the west façade is supported through a two-way cable net system, which is anchored to the ground and roof level and the shear walls at each end of the building, and a pair of cantilevered feature stairs, which serve as entry features to the library.

Although the final structural system of the building is relatively simple, the collaborative process required for such a complex, integrated design proved to be the real challenge. Several structural systems, including cast-in-place, precast concrete, and many combinations of the two, were studied before the final system was agreed upon by the team as the most cost-effective, easiest to erect, and least disruptive to the transparency of the architecture.

To minimize costs, every structural component of the building was scrutinized by the design team and Pepper Construction, starting with the foundations. Most four-story, concrete buildings in Chicago can be founded on spread footings. However, with the heavy precast slabs and a spacious 30-foot by 30-foot grid, and the soil condition just 30 feet from the shore of Lake Michigan, the spread footing option was not viable. A continuous mat or deep caisson foundations were the remaining available options. Loyola was wary of the caisson option, since they could not recall if the Lake Michigan seawall tiebacks, which would be located right below the new library, still existed. There were also indications that the tie-backs, if remaining, were still an integral part of the seawall. Pricing of the two foundation schemes favored the caisson option by nearly 20 percent, so it was necessary to verify if in fact the tiebacks remained. A deep earth scanning over the site was performed and the analysis concluded that the tiebacks had been removed. The scheme moved forward with a caisson foundation.

As with the foundations, the gravity load carrying system went through several design iterations as well to minimize cost and integrate the architecture with the mechanical systems. Since the slabs were to be used as a thermal mass for radiant heating and cooling, they had to be exposed. A 9-inch, two-way, post-tensioned floor slab would have been ideal but was eliminated in favor of a one-way slab with girders to support the large, curved slab openings that were integral to the lobby and elliptical stair designs. As the design evolved, Transsolar indicated that greater surface area would improve the performance of the radiant slab, while SCB was promoting a structural floor with a constant depth. Ultimately, everyone agreed to girders with a one-way concrete joist system, although SCB felt that the barrel-shaped profile between the joists was more aesthetically pleasing and would also integrate better with its lighting design concept.

Halvorson and Partners Minimal structure inherent in this project is evident in the cantilever feature stairs for the information commons.

Unfortunately, this mutually agreeable solution for a cast-in-place, barrel-vaulted joist system would be costly to construct. Pepper Construction would be forced to decide between building many barrel vault forms to be used only once or twice and sacrificing valuable schedule time in order to reuse a limited number of custom forms.

It was clear that the barrel vault slabs would be the most cost-effective if they were precast. With this decision, the design team revisited the concept for the whole building to be constructed from precast components. Although precast columns and girders would have been less expensive, the cantilevered spans and curved girder profiles could not be achieved easily with precast, and the corbels required for the girder-to-column connections would clutter the clean, exposed structure SCB envisioned.

The ideal shape for the precast slab is 16 inches deep by 10 feet wide and typically 30 feet long. Fortunately, the barrel profile worked with the lighting design and the radiant heating and cooling. The precast subcontractor, Advanced Precast, could easily produce all the typical and atypical lengths of slab while the columns and girders were being formed and placed for each level. Also, installation of the radiant tubing into the barrel vault forms was simpler in the controlled environment of the precast plant. With the win-win solution that this decision provided, the design team could see that the iterative solutions and team collaboration was worth the effort.

The post-tensioned girders were designed such that the bottom of the girder matched the bottom of the barrel vault slabs and the profile of the exposed edge of the girder gave the appearance of a thinner element. However, a 16-inch-deep girder was not sufficient for the 30-foot spans, even if post-tensioned, so the girders were extended above the top of the precast slabs and into the raised floor system.

As a final cost-saving measure, the precast barrel vault slabs and cast-in-place girders and columns were used only within the middle 70 percent of the building — the area with the exposed structure, an integral part of the transparent architecture. The structure within the solid-looking “bookends” at the north and south ends of the project is comprised of precast columns, girders, and hollow core plank. In lieu of using cast-in-place or precast shear walls, clad in the stone to achieve the aesthetic of the bookends, architectural precast walls were designed as both the gravity and lateral force resisting system.

Richard J. Klarchek Information Commons at Loyola University Chicago Owner Loyola University Chicago Structural engineer Halvorson and Partners, Chicago Design architect Solomon Cordwell Buenz, Chicago Contractor Pepper Construction, Chicago Construction manager Pepper Construction, Chicago Geotechnical consultant AECOM (formerly STS Consultants), Chicago MEP engineer Elara Engineering, Chicago Climate engineer Transsolar Klima Engineering, Germany
By the numbers:	Richard J. Klarchek Information Commons at Loyola University Chicago
Size, shape, and type
Number of square feet:	67,000
Number of stories:	4
Structural system types:	Precast barrel vault floor structure (and exposed ceiling) with integrated radiant heating/cooling; supported by cast-in-place post-tensioned girders and cast-in-place floor structure
Foundation type:	Grade beams supported on belled caissons bearing on stiff clay (hardpan) approximately 65 feet below grade
Construction quantities
Tons of structural steel:	20 (at the fourth floor conference room enclosure)
Barrel vaulted slab sections:	125
Square feet of deck:	60,000
Number of footings/piers:	32 belled caissons
www.vitopalmisano.com Spotlight: Halvorson and Partners Q&A with the SE Halvorson and Partners (HP) Principal Gregory J. Lakota, S.E., P.E. (GL), discussed aspects of the Richard J. Klarchek Information Commons at Loyola University Chicago with Structural Engineer Editor Jennifer Goupil, P.E. (JG). JG: What inspired you during the design process for the Commons? GL: I was inspired by how much energy the building was going to save and that there was an opportunity for the structural design to be integrated into the energy-saving mechanical system. JG: What was your first task to get started on the design? GL: As with most projects HP is involved with, the first step in the collaborative design process is to talk with the owner and architect to find out their goals and vision for the project. Then we start to layout a range of structural options that could complement the vision. For the Commons, there were two keys to the vision: transparency and energy efficiency. Because the project is situated on the last remaining lake-front site for Loyola’s main campus, the university and architect envisioned as transparent a building as possible to maintain views of the lake. However, neither the university nor the design team wanted to compromise energy efficiency to achieve this visual transparency. The university remained focused on the long life cycle and energy costs for the project. JG: What types and how many structural systems did you and your team evaluate for this project? GL: Various combinations of plain reinforced and post-tensioned cast-in-place concrete versus precast columns, walls, and slabs and girders were studied to determine the most cost-effective option. A key charge was to find the most cost-effective solution to achieve an absolute minimum floor structure depth (for transparency mentioned above) while integrating the PVC piping for the radiant heating/cooling system (for efficiency mentioned above). The feature stair structure also needed to be as transparent as possible, so we avoided columns or hangers and again designed the structure with absolute minimum depth. JG: Did this project have owner-required sustainable design goals such as USGBC LEED or Green Globes? GL: Loyola University had energy efficiency and cost goals for this project; they did not have a LEED certification goal. However, because long-range planning for minimizing energy use drove the energy-efficient design, the project ultimately achieved a LEED Silver rating. Firm Facts Halvorson and Partners is headquartered in Chicago and was founded in 1996 by Principal Robert A. Halvorson, S.E., P.E., F.IStructE. The company employs 42 people and provides services for new construction, existing building renovation, forensic engineering, and expert witness in the commercial, residential, hotel, education, healthcare, retail, and convention center markets.

Gregory J. Lakota, S.E., P.E., is a principal at Halvorson and Partners. He has spent the last 17 years collaborating on landmark projects — from iconic high-rise towers to intricate museum and university buildings. He can be reached at 312-274-2403 or via e-mail at glakota@halvorsonandpartners.com.