In today’s world, so-called “high-performance, sustainable” facilities are a dime a dozen. But many of these buildings rely on overly complex mechanical systems to carry out their mission. While these systems may meet design requirements, they routinely fall short of performance expectations — a direct result of the mismatch between elaborate systems and the often-limited resources of the facilities personnel expected to operate them.
The new Ray and Joan Kroc Corps Community Center in Chicago’s West Pullman neighborhood posed a unique challenge to local MEP designer ESD (Environmental Systems Design, Inc.): to deliver a high-performance, sustainable building while incorporating MEP systems that are manageable and fit for purpose.
Featuring an aquatic center, sports training facilities, a gymnasium, classrooms, offices, and a 600-seat auditorium, Chicago’s 160,000-sq-ft Kroc Center also required a diverse MEP design to meet the demands of different environments under the same roof with systems that can be monitored and controlled on site and remotely, around the clock by both highly skilled and novice facilities personnel.
Key to successfully meeting these challenges was prioritizing, in order, passive strategies, then highly efficient mechanical systems, and finally incorporation of a robust and highly con-figurable building monitoring, automation, and control system. Brought on board early in the design process by developer International Facilities Group (www.ifgroup.cc), Chicago, ESD was first tasked with quantifying the energy benefits of various passive efficiency strategies under consideration. Through detailed understanding of stakeholder preferences and collaboration with the entire design and construction management team, with a focus on total cost of ownership and innovative use of proven technologies, ESD designed environmentally conscious MEP systems that fit the budget, are practical to operate and maintain, and can reliably provide comfortable and productive environments that support the Kroc Center mission.
Working closely with Antunovich Associates (www.antunovich.com), Chicago, the project’s architect, ESD first looked at the building’s massing and orientation and performed preliminary energy modeling analysis using DOE-2 software, eQUEST 3.63. This analysis served to quantify various opportunities utilizing available solar resources to heat the building’s interior spaces. For example, since both the Kroc Center indoor competition and leisure pool environments need to be heated year-round, they were designed at the southern wall in order to benefit from southern sun exposure.
The glazing and lighting control system throughout the building was engineered to balance two conflicting ideals: to maximize solar visible light transmittance limiting artificial light usage and to minimize thermal conductive losses through the building envelope associated with additional glazing. Early coordination with the architectural and construction teams also included detailed evaluation of appropriate envelope construction including vapor barrier location, insulation R-values, glazing U-values, and glazing shading coefficients. Together, these steps, informed by detailed energy analysis, resulted in a building envelope that incorporates best practices, is code compliant and accommodates project energy performance goals (Figure 1).
Once passive strategies were incorporated into the design, the next step was to select the MEP systems. With critical input from WE O’Neil (www.weoneil.com), Chicago, the project’s general contractor, construction, energy, and maintenance costs were carefully considered to identify systems with the lowest total cost of ownership.
HEATING AND ENERGY RECOVERY
In order to meet the building’s large space and service water heating demand for its pools, showers, and locker rooms, a modular variable flow, high-efficiency natural gas condensing boiler arrangement was designed. Four relatively small modular boilers (39 boiler hp/each) were specified to meet Chicago’s high winter heating demand with high turndown capacity to efficiently meet the lower (but still significant) summertime demand.
As an energy conservation measure, heat recovery from the pool dehumidification process was used as the first source of heat for the pool water. While waste heat from the dehumidification process is typically rejected via condenser coils to the outdoors, the year-round heating requirement for the Kroc Center pool water provided a unique opportunity to take advantage of this conflicting process, transferring the heat from one process to another.
To serve a diverse community with demand for both family recreational and adult fitness facilities, the Kroc Center includes two distinct aquatic environments, each with unique space and water temperature requirements. Two pool dehumidification units serve the leisure pool and spa area (DHU-1 and DHU-2), while another unit serves the competition pool area (DHU-3). Each dehumidification unit was designed with a single heat recovery loop with the waste heat from DHU-1, DHU-2, and DHU-3 providing the first source of heat for the leisure pool, the spa, and the competition pool, respectively.
Consideration was given to the development of a centralized energy recovery system to facilitate greater energy recovery from the dehumidification systems for input into the hydronic heating system. Given the high heating demand of the leisure and spa pool areas, careful analysis revealed that the theoretical energy efficiency improvement achieved through the utilization of the remaining waste heat was very nearly offset by the increased distribution pumping energy necessary to be interconnected to the hydronic heating system. Again, detailed analysis of a great idea resulted in avoided cost and avoided system complexity in favor of practicality and equivalent effectiveness.
The large exhaust and ventilation requirement for the locker rooms also presented an opportunity to recover waste heat. A dedicated packaged energy recovery unit was designed to fix the ventilation and conditioning needs, while recovering energy from the exhaust airstream. An air-to-air plate type heat exchanger was selected to conform to local prohibition on any communication between exhaust and ventilation air streams in this application. Despite such prohibition precluding the use of total enthalpy wheels in this application, the unit is still able to recover 58% and 67% of the sensible energy during cooling and heating, respectively.
COOLING AND VENTILATION
When designing the cooling and air distribution, the team looked at multiple options:
- Option 1: Chilled water plant
- Option 2: Evaporatively cooled rooftop AHUs
- Option 3: Water cooled direct expansion (DX) rooftop AHUs with central condenser water system and cooling tower
- Option 4: Water cooled DX rooftop AHUs with ground coupled heat rejection system
- Option 5: Air cooled DX rooftop units (DX RTUs)
A detailed cost comparison was performed that included typical evaluation of installed and energy costs and which also studied the impact on the number of operating personnel required to properly maintain the various systems. Total building energy performance was carefully evaluated for each option, with a keen eye on the details.
It is often assumed that evaporative cooling systems (whether centralized chiller plant or water/evaporatively cooled DX units) are significantly more efficient than their air cooled DX counterparts. It is critical that performance evaluations account for nuanced system details and not simply published equipment efficiencies. For example, factors such as the addition of glycol or recirculation pumps for freeze protection of chilled water systems and chilled/condenser water pumping energy significantly affect overall system performance and must be accounted for properly.
In this case, given the amount of horizontal piping distribution, associated pumping energy and need for freeze protection, it was found that specifying premium efficiency air cooled DX rooftop units with high energy efficiency ratios (the units specified had typical EER values over 11), the system was only marginally less efficient than a evaporatively cooled or ground coupled system, while still exceeding the ASHRAE 90.1-2007 minimum energy performance. Critically important to the system selection was the fact that, compared to the alternatives, the air cooled DX RTUs would simplify and streamline the center’s mechanical infrastructure from a controls and maintenance perspective. The considerable maintenance burden and costs associated with managing an evaporatively cooled system were not justified in this case, given the marginal energy benefits.
The owners and developers of the Kroc Center had a clearly defined vision for their BAS. The BAS had to be reliable, configurable to serve users of varying levels and web-enabled to facilitate remote monitoring and operation. In support of the Salvation Army’s mission to provide job training and development of individuals from the community, it was essential to design the control system to accommodate users with varying experience levels, while providing the most experienced engineers with the capacity to remotely monitor and operate the facility as well.
The Honeywell WEBs-AX BAS platform specified utilizes a Web Supervisor (server application) and four JACEs (i.e., Web integration controllers). Honeywell ComfortPoint BAC-net DDC controllers were installed to monitor and control all HVAC equipment, while other equipment with communicating packaged controls was also integrated to the BAS. This open and highly configurable framework allows for review and adjustment of any parameter from any remote location — essential to a chief engineer managing the 24/7/365 not-for-profit facility without the benefit of second and third shift expert support. The BAS design features alarms and alerts that are sent directly to the chief engineer’s email, alerting him immediately of any situations that arise. The system’s remote monitoring and control capabilities are also used by Kroc Center facilities personnel as a training tool, allowing the chief engineer to remotely login to demonstrate appropriate response and system adjustments to less experienced engineers seated onsite at the operator’s workstation.
Creating a facility based on sensible design was a chief goal for the Kroc Center, Chicago. Targeting LEED® Silver, the center features a number of other sustainable elements, including a daylight dimming system throughout the perimeter spaces of the facility, a 32,700-sq-ft green roof and low-flow plumbing fixtures throughout the locker rooms, toilet rooms and pantries.
Beginning with efficient and practical mechanical systems, a flexible BAS and other sustainable measures, the building’s exterior envelope and MEP systems come together to create a building that is as practical and unique as the Kroc Center vision itself.