Exploring the high demands for higher education facilities: HVAC
The design process for higher education facilities has its own set of challenges and requirements. Engineers discuss the current trends, challenges, and experiences with college and university facility projects regarding HVAC.
Keith Hammelman, PE, Senior Vice President, CannonDesign, Chicago
Tom Hickey, PE, Plant and Building Services Market Leader, Stanley Consultants, Muscatine, Iowa
James Newman, PE, CEM, BEMP, LEED AP BD+C, High Performance Design Team, Leader, EYP Architecture & Engineering, Boston
Jose I. Torres, PE, MBA, Project Manager/Mechanical Engineer, RMF Engineering Inc., Raleigh, N.C.
CSE: Have you specified distinctive HVAC systems on any college/university projects? What unusual or infrequently specified products or systems did you use to meet challenging HVAC needs?
Fisher: We have used geothermal heat pumps at the College of Marin and Ohlone College located in northern California. These projects were challenging to design in terms of available space for wells, and it was difficult to fine-tune the controls. Getting the timing right on the scheduling and commissioning all of the components were demanding tasks.
Foster: Double-wall façade is a system that we have applied for several university projects. This system was used to reduce peak loads and allow for downsizing or use of radiant-based heating/cooling solutions.
CSE: Have you specified variable refrigerant flow systems (VRF), chilled beams, or other unique HVAC systems into a college/university building? If so, describe its challenges and solutions.
Foster: Valence units in resident hall applications save on floor space and eliminate fans, which results in lower maintenance.
Fisher: For Soka University of America in Aliso Viejo, Calif., we are designing a VRF system as part of the overall energy efficiency strategy. We have used chilled beams for Las Positas College in Livermore, Calif. These systems are straightforward, easy to maintain, and energy-efficient, with the biggest hurdle being capital costs and commissioning.
CSE: What unique HVAC requirements do such projects have that you wouldn’t encounter in other projects?
Hammelman: A unique aspect of college and university projects is that you will actually encounter a wide variety of building types that require different types of HVAC systems to meet the demands. A typical college/university may have residence halls, classrooms, laboratories, health care buildings, performing arts, recreation centers, and sports arenas. These varying building types require an HVAC engineer to plan on using a different type of HVAC system to suit the needs of the building. For example, a residence hall may be served from a VRF technology, and a performing arts facility may be better suited to be served from a displacement ventilation system.
Fisher: With indoor air quality being a primary consideration of today’s buildings, we have done computation fluid dynamic air transfer analyses on laboratories to ensure we aren’t transferring hazardous fumes to other parts of buildings.
Newman: Working on college/university campuses provides a unique set of opportunities, given the multiple and differing building types, each with its own set of user requirements. The best way for design engineers to mitigate the challenges of tackling new high-performance design strategies is to conduct as much early research/analysis as possible and communicate their findings with the owner and design team for integrated discussion and informed decision making. Communicating the potential challenges as well as any energy/financial analysis can often eliminate any unsuitable options right from the start. With a narrowed focus, this can allow more time and effort to be spent on design options with high potential for success within the project, as determined by the performed analysis.
Foster: Radiant-based cooling projects require special attention to the internal and external cooling requirements, infiltration control, and latent loads. Loads need to be low enough to allow for chilled sails or chilled ceilings to be used, infiltration needs to minimized to avoid condensation, and the latent loads need to be controlled through the air system.
CSE: When retrofitting existing facilities, what challenges have you faced and how have you overcome them?
Hickey: Existing ductwork is often not well-documented and not accessible for field verification. The flow path needs to be confirmed through field testing.
Hammelman: Retrofitting existing facilities is always a challenge, because you are often constrained by the existing structural systems or the fact that the facility must remain operational during construction to serves\ a crucial need to the college that isn’t replicated elsewhere on campus. Take, for example, the HVAC system replacement project we completed for the University of Chicago’s law library. This project required us to keep the facility operational during the HVAC system replacement while working within a building with about 12 in. of clear space for horizontal distribution at each floor. The limited existing clear space at each floor level required the use of a vertical distribution system for the low-pressure supply ductwork. All of the medium-pressure ductwork and associated terminal air boxes were located within the penthouse space, and vertical distribution controlled by VAV boxes at the top level of the facility (ventilation risers) was routed in multiple locations through each floor of the building. To maintain occupancy of the facility during construction, we provided a temporary exterior-mounted air handler to supplement the existing systems while they were reconfigured during construction, with temporary distribution routed exposed at the 6th floor while the interstitial distribution was replaced.
Torres: One of the challenges we’ve faced is documenting the existing performance of the HVAC systems versus the “as-built schedules.” We’ve combated this problem by performing an “as-found conditions survey” of any existing HVAC system that will be reused in an existing facility. We typically hire a test-and-balancing agency to measure the existing conditions of any fans, pumps, and AHUs that will be reused in a project. This exercise will allow you to proactively correct any deficiencies in the existing system and provide you with real-time performance of the MEP systems.
Foster: We recently completed the renovation of a 120,000-sq-ft 1950s-era university building that previously only had window air conditioners and a challenging floor-to-floor height. The low floor-to-floor height required ductwork to be minimized, so a radiant-based heating and cooling system was used for all offices and classrooms. Additionally, liquid desiccant dehumidification was used to address peak latent loads.
Fisher: Meeting energy efficiency requirements is the biggest hurdle with existing buildings. We often find restricted space on roofs that are not structurally sufficient to support new equipment, such as economizers, chillers, cooling towers, and other equipment that replaces inefficient rooftops of through-the-wall units.