David Rubenstein Forum
Firm: Primera Engineers, Ltd.
Owner: The University of Chicago
Description:Original or Innovative Application of New or Existing Techniques: The Rubenstein Forum has a make-up air handling unit, two dedicated outside air handlers (DOAS), and two variable air volume (VAV) air handling units with energy recovery to provide conditioned air to the spaces during all occupied hours. These units are heated by a hot water system served by three high efficiency gas boilers and cooled by a chilled water system served by two heat exchangers, which draw from the existing campus chilled water loop. Most of the net square footage of the Rubenstein Forum utilizes demand-controlled ventilation through carbon dioxide sensors and occupancy sensors; these sensors can also override the BAS controls, if needed. VAV boxes are implemented throughout the building to ensure enough conditioned and ventilation air reaches each space based on desired temperature and humidity.
In addition to the energy recovery (both single wheel and series wheel arrangements) on the air handling units, staggered startup of equipment to minimize peak in rush current and campus global zone temperature resetting allows the University to better manage peak energy use. The building also uses chilled beams in an innovative way for cooling and heating. It draws its chilled water from the campus chilled water loop while using heat exchangers to serve as a pressure break between the campus and building cooling systems. In addition, it uses multiple secondary loops to allow for higher temperature differentials. VAV boxes are also implemented in a creative way so that every space is properly ventilated while continuously adjusting outside air rates to zones, along with zone temperature setpoints. The Rubenstein Forum air handling systems utilize fan arrays (with individual fan control within the array) allowing for a large, stable operating range. Multiple fans within each array can shut down, not just modulate, to provide greater flexibility and fan energy savings. The building also contains a dedicated make-up air system serving only the kitchen which includes high efficiency kitchen exhaust fume hoods that regulate exhaust and make-up airflow (energy) based on cooking intensity and occupancy to provide some additional energy savings.
Future Value to the Engineering Profession and Perception by the Public: The interior of the Rubenstein Forum, and its systems, are just as stunning and imaginative as the building’s exterior. The architect’s unique design lent itself to some creativity when designing the engineering systems and sparked a fresh take on making it more energy efficient and sustainable. In addition to the use of energy recovery in such a unique building, the Rubenstein Forum implements chilled beams tapped off of the existing campus chilled water plant for perimeter cooling. Chilled beams are still on the rise as a viable perimeter cooling option, so the Forum could serve as a pioneer for the advancement of this cooling method. Special care was also taken in designing the air handling unit fan arrays in the facility. They allow for individual fan control within a single array, which allows for a large operating range. Additionally, multiple fans within each array can modulate or shutdown to provide greater flexibility and fan energy savings, even during the COVID-19 pandemic. Finally, the dedicated make-up air system serving only the kitchen with high efficiency exhaust hoods allow for better regulation of fumes and provide additional energy savings.
Social, Economic and Sustainable Design Considerations: The University of Chicago is committed to achieving a sustainable campus, with a goal to reduce University greenhouse gas emissions by 50% before 2030. Considering campus buildings contribute to approximately 70% of the University’s greenhouse gas emissions, high-performance buildings are a top priority for the University. Awarded LEED Gold status for sustainable design, the Rubenstein Forum helps with this goal. The HVAC design includes a dedicated outdoor air system with energy recovery and chilled beams, using campus chilled water for cooling and condensing boilers for heating. The electrical design included the necessary power distribution for building systems and operations and for audio-visual needs. Energy services included development of the whole building energy model, including façade analysis optimization and life cycle cost analyses of various system options. While a concrete payback period is unknown, 29% annual energy cost savings compared to an average building of this type is substantial and will provide a return on investment every year, thanks to models done by the architect and the structural engineering consultant. A 40% reduction of energy use (compared to ASHRAE 90.1-2007 levels) will have a positive effect on the environment. As a result, nine LEED points were achieved from the Energy and Atmosphere Optimize energy performance. In addition, the Rubenstein Forum has a relatively low reliance on natural gas/fossil fuels compared to its use of electricity, which further increases its positive environmental impact. In terms of site EUI, the proposed model improves by 40%.
Complexity: The building’s cantilevered, post-tensioned structural design demanded highly coordinated pathways for the building’s systems, especially within the tower section. To maximize program space on every floor, equipment was placed in highly shielded locations on the roofs with shaft space minimized using a decoupled ventilation system. A perimeter heater was required for each cantilevered floor which was coordinated in structural shallow trenches to allow floor spaces to be maximized while providing a highly effective heating system for human comfort. Additionally, because of its intricately designed structure, the Rubenstein Forum has a much higher difference between gross sq-ft. and net sq-ft. than a typical structure of this type. This made it difficult to model and size mechanical equipment because the load calculations became much more complicated. This resulted in the need for higher level care to be put into the calculations of the project and required many iterations as the building itself became more refined over time. In addition, having to tie into an existing chilled water plant that serves a large campus was not an easy task. But this was required to implement the innovative chilled beam design for perimeter heating. Great care and thorough analysis were needed to ensure that the existing plant was not adversely affected.
Exceeding Owner Needs: Primera, and the rest of the project team, ensured that two of the University’s most important goals were met upon completion of the Rubenstein Forum - using sustainable practices and materials and having a positive impact on our surrounding community. Primera’s work featured a flexible and energy efficient HVAC design as well as an electrical design that includes the necessary power distribution for building systems and operations in addition to audio-visual needs. The use of energy recovery wheels, temperature setbacks, occupancy sensors, lighting controls, and demand control ventilation are inherent in the BAS control strategy. Likewise, Primera’s team developed the whole building energy model, including life cycle cost analysis of various options, resulting in notable energy savings. In response to the client’s second goal, the recently completed project not only brings much needed meeting and event space to the University’s campus and its faculty, but it also offers an inspiring all-purpose space for the local community and clients outside of the university that promotes an open exchange of ideas.
The University of Chicago