Examining higher education facilities: HVAC and plumbing
John Holbert, PE, LEED AP, Senior Principal/Client Executive, IMEG Corp., Rock Island, Ill.
Donald Horkey, PE, LEED AP, Principal, DLR Group, Minneapolis
Kent Locke, PE, NCEES, Associate Principal/Branch Manager, Bailey Edward, Fox River Grove, Ill.
Dennis P. Sczomak, PE, LEED AP, Senior Vice President, Peter Basso Associates, Troy, Mich.
Blake Smith, PE LEED AP, Project Manager, RMF Engineering, Raleigh, N.C.
Jason Sylvain, PE, Partner, National Higher Education Practice Leader, AKF Group LLC, New York City
Matthew Wiechart, PE, CxA, LEED AP, CEM, Principal/Senior Mechanical Engineer, TLC Engineering for Architecture Inc., Orlando, Fla.
CSE: What unique heating and cooling systems have you specified into such projects? Describe a difficult climate in which you designed an HVAC system.
Horkey: With the prevalence of high-performance HVAC systems requiring year-round chilled water and the predominance of high-pressure steam distribution systems on campuses, we have seen an increase in alternative chilled-water generation systems designed into projects. For example, using dry coolers for chilled water generation in winter for cold climates. There also has been more emphasis on absorption and electric chillers in combination to generate campus chilled water. This allows the institution to use real-time pricing to inform which equipment will be used for chilled-water generation.
Smith: We provided the design to renovate an existing space to become the lab for an electron microscope, which is an extremely precise piece of equipment that needs a critically stable environment to operate correctly. The room cannot fluctuate by 0.25°F over a 20-minute period, and temperature must be maintained while minimizing any air velocity. Other constraints included the room’s ambient noise-pressure levels had to be very low, so the HVAC and room construction had to be designed to limit noise we created and mitigate exterior noise.
Sylvain: Working in the Northeast, the climate is less difficult and more of a benefit. On a recent project, our company was able to use natural ventilation to provide code-required ventilation for a 100,000-sq-ft consolidation of a university’s humanities department. The project uses perimeter heating and cooling systems (fan coils and valance units) with operable windows for ventilation. In addition, this project has been designed to meet LEED v3 and will be occupied in the fall of 2020.
Wiechart: Design of chilled-beam systems in hot-humid climates has gained traction. There are at least three in the central Florida area for college and universities. These systems require dedicated outdoor-air systems that mitigate moisture in the airstream. The systems are energy-efficient as compared with a typical chilled-water distribution with VAV systems. Another unique design is using the indoor air quality procedure to limit ventilation to the building. By using an absorptive filtration system, outdoor air to the building can be reduced when compared with the ventilation rate procedure (typical design).
Locke: One university has an existing geothermal field they want to use for a new building on campus. Through data logged over time and information regarding the soil conditions, we were able to determine the field was adequate for the heating. However, we need to add supplemental heat-rejection equipment for the cooling cycle. The geothermal field would be the first stage and the cooling tower the second stage to meet the load requirements of the new building.
CSE: What unusual or infrequently specified products or systems did you use to meet challenging HVAC needs?
Wiechart: Geothermal systems coupled with water-source heat pumps help provide individual control in student housing projects while maintaining energy efficiency.
Sylvain: Over the past couple of years, our company has been working with multiple universities to design systems with valance units at the perimeter. Valance units are passive heating and cooling systems typically installed at the perimeter ceiling of a space. They are essentially a dual-temperature coil inside an architectural enclosure with an integral condensate drain pan. They induce airflow through the coil, heating or cooling the spaces.
Smith: Our design incorporated a decoupled chilled-water system for radiant-chilled wall panels to minimize room temperature swings and handle sensible loads. A separate blower coil with building chilled-water sound attenuation for humidity control and space pressurization were used.
CSE: What types of high-velocity, low-speed (HVLS) fans or other strategies are owners and facility managers requesting in such facilities?
Sczomak: We have used high-volume, low-speed fans, which are particularly well-suited for high-bay rooms in college/university athletic facilities. We have used them to provide air movement, attaining the same level of athlete comfort at a higher room temperature, thus reducing air conditioning demands. During winter, the HVLS fans also reduce the stratification of warm air in the upper part of the room, reducing heat loss through the upper walls and roof. Care should be taken to coordinate placement of these fans with lighting to avoid unwanted strobe effects.
Smith: Our company has incorporated HVLS fans in fitness centers for both the looks and conditioning of occupants. The HVLS fans give the opportunity to raise the space temperature setting if desired.
Wiechart: In automatic-retrieval facilities, these systems are used to mix air without the incorporation of ductwork. In recreation and wellness facilities, the equipment is used as an architectural feature and again to mix the air while minimizing ductwork.
Horkey: Depending on the type of facility, the architectural design of the facility drives the types of destratification strategies and fans we have implemented. Owners, facility managers, and the design communities’ understanding of how to apply this technology, and the benefits to occupant thermal comfort and energy savings, is pushing the use of these systems.
CSE: What types of air balancing do you typically include in your designs? Describe an example.
Sylvain: Depending on the type of project (new, gut renovation, or cosmetic renovation), AKF has different levels of balancing that we design into our documents. For a new or gut renovation project (with all new equipment), we typically would provide for full testing and balancing of all new hydronic and airside systems at the completion of the project. This testing would be completed by a National Environmental Balancing Bureau (NEBB) or Testing, Adjusting and Balancing Bureau (TABB) certified professional and verified by the commissioning agent. For a cosmetic renovation or gut-renovation project (using some existing equipment), we would typically ask the university to take prereadings on all equipment anticipated to be reused. Then, assuming the existing equipment has adequate capacity, we would design our documents to provide full testing and balancing for all existing and new hydronic and airside systems at the completion of the project. This testing would be completed by a NEBB- or TABB-certified professional and verified by the commissioning agent.
CSE: When working on educational facilities, describe the HVAC ventilation system, which might include hoods, fire-suppression systems, or other specialized ventilation systems.
Locke: The ventilation load in educational facilities is higher due to the large people load. In some cases, the HVAC system is used more like a make-up air unit, or what they call a dedicated outside-air unit (DOAS). The return/exhaust from the spaces served by the unit typically enters an energy recovery unit, which will preheat/precool the outside air prior to exhausting this air. Terminal AHU units provide the additional heating and/or cooling required to maintain space setpoints. The return/exhaust air quantity is typically less than the supply air since there is toilet exhaust, fume hood exhaust, and kitchen hood exhaust that might also affect the overall balance of the building.
Wiechart: A ventilation system for educational facilities is not a one-size-fits-all answer. General office space typically will have an AHU mix air in the return airstream to provide ventilation. Large classrooms typically will have a dedicated unit with dedicated outdoor-air coils to condition the outdoor-air ventilation due to the required volume. Student unions will have systems that deliver air to the dining and kitchen areas as dedicated outdoor-air system to make-up air to these spaces. Finally, research labs that have many lab hoods will have variable air systems that have dedicated outside air. The air will vary based on space pressurization and hood-sash positioning. These systems use fast-acting valves and sophisticated controls.
CSE: How have you worked with HVAC system or equipment design to increase a college or university’s energy efficiency?
Smith: Large assembly spaces are being designed from a programming perspective to be extremely flexible to the occupant for many uses by all groups on campus. This produces a challenge from an HVAC perspective to design a system that can handle the peak worst-case scenario condition but also turn down efficiently for most normal use. AHUs will typically be VAV and track carbon dioxide to modulate outside-air rates. Reduction in outside-air intake when it is not needed can result in significant savings. Airside economizer controls also allow for free cooling during certain times of the year.
Wiechart: Energy efficiency starts at the inception of the project by evaluating building architecture for insulation and fenestrations as well as massing and orientation. Using early energy models to evaluate multiple design approaches and design decisions as they relate to energy and cost can be evaluated and vetted. Through this iterative process, systems can be selected and designed. The major energy-conservation effort is on the operation of the system through controls. Setbacks, occupancy, and optimization of the system is the key to better energy conservation.
Sylvain: In most universities and based on the energy code, it is common to design an HVAC system to include a heat-recovery system. On a current project, our company is working to design a system that uses both heat recovery and then relief air as outdoor air to a make-up air unit (MAU). This system is a double win in terms of energy efficiency. The AHU with the heat-recovery system has a very large occupancy load that is driving up the outdoor-air requirements, and the MAU serves a kitchen. On this project, we have designed the kitchen to have a wider temperature range than normal occupied spaces. This allows the return air to pass through the heat-recovery system, becoming relief air that would typically be exhausted out of the building. During specific conditions, the relief air is directed back to the outdoor intake for the MAU. This allows the MAU to see a reduced load and the university to benefit from maximum energy efficiency from the systems.
Horkey: There are numerous ways that we have helped our clients improve campus energy efficiency. Campuswide energy master plans are a great tool to assist campuses at a high level and establish overarching energy goals. Performing individual building retro-commissioning projects is a great way to tune up the building and identify potential HVAC system or equipment improvements. Once the issues and solutions have been identified, design and implementation strategies can be incorporated to correct the issues. When the design and construction is completed, the new strategies can then be optimized by commissioning the new work.
CSE: Describe a project in which you specified a specialty piping, hydronic, or pumping system for such a facility.
Wiechart: Trevor Colbourn Hall used chilled beams for cooling spaces. The system uses polypropylene piping, which was not insulated to provide that chilled-beam water to the chilled beams. The piping is thermally welded with some resistance to condensation, versus a metallic piping system (copper or steel). The ability to not insulate the piping system saved costs, which allows the system to have a better return on investment. With the chilled-beam system design, the return water from air handling equipment is distributed through a separate piping and pumping system, which increases the chilled-water temperature difference. This greater temperature difference reduces overall pumping flow needs and increases chiller plant efficiency.