Building efficient colleges and universities: HVAC and sustainable buildings/energy efficiency
- Don Harrisberger, PE, LEED AP, Principal Engineer, Southland Engineering, Los Angeles
- Timothy J. LaRose, PE, Vice President Development, Education & JENSEN HUGHES Academy, JENSEN HUGHES, Warwick, R.I.
- Julianne Laue, PE, LEED AP, BEAP, BEMP, Senior Energy Engineer, Mortenson Construction, Minneapolis
- Robin Mosley, PE, LEED AP, Associate Partner, Syska Hennessy Group Inc., Newport Beach, Calif.
- Liza Sandman, PE, Project Manager, RMF Engineering, Charleston, S.C.
- John Teeter, PE, Mechanical Department Manager, Dewberry, Raleigh, N.C.
CSE: What unique HVAC requirements do college and university facilities have that you wouldn’t encounter in other buildings?
Laue: College and university facilities vary in nature and can include many building types including residence halls, dining facilities, classrooms, offices, labs, medical, parking, etc. Each building type has their own HVAC design requirements with differing maintenance requirements. Understanding the facility maintenance team’s tolerance for newer systems, different manufacturers, new sequences of operation, etc. is key to developing HVAC requirements for new or renovated buildings. By looking at the design through a total cost-of-ownership lens that includes maintenance and replacement of systems as well as operator experience with the HVAC system, the true value of the designed systems can be identified.
Mosley: Most campuses have central chilled-water, steam, or hot-water utilities. These are brought into the building to serve built-up air handling units (AHUs) and heat-exchange equipment. Many universities meter these services to provide accurate billing of the energy usage for each individual building. Integrating these systems for the benefit of the whole campus is critical. Maximizing the Delta T of the chilled water on the campus central plant is done through smart use of these services within the new or renovated building and their associated terminal AHU coils, heat exchangers, etc.
Teeter: Many college and university buildings have multiple functions or usage in the same building. One building may house laboratories, research spaces, administrative spaces, lecture halls, and classrooms, all of which may have vastly different requirements for temperature, humidity, filtration, exhaust, and ventilation.
CSE: Have you specified distinctive HVAC systems on any such facilities? What unusual or infrequently specified products or systems did you use to meet challenging HVAC needs?
Teeter: In a recent project, one research area required lower temperature and humidity setpoints that could not be achieved with traditional HVAC systems. This single space in a much larger building required a separate desiccant system to achieve the design criteria. In addition to the desiccant system design requirements, thermal and vapor barrier separation from the surrounding spaces needed to be carefully coordinated with the design architect.
Mosley: I have used vertical flooded shell and tube heat exchangers to replace inefficient pressure-reducing stations on select projects. This method enhances the building and campus energy efficiency when steam is used.
CSE: Describe situations in which you designed unusual acoustics or sound-dampening systems for college or university facilities. What were the challenges, and how did you resolve them?
Harrisberger: LEED for schools imposes challenges to HVAC design that require us to work closely with acousticians to meet the 45dBA requirement and limit sound between classrooms. Equipment placement and isolation are important to ensure vibration and noise do not transfer to learning spaces. Selection of air distribution is important to meet both the thermal demand as well as acoustics. The return-air path also needs to be addressed to limit sound transfer between spaces.
CSE: Have you specified variable refrigerant flow (VRF) systems, chilled beams, or other types of HVAC systems into one of your college or university structures? If so, describe its challenges and solutions.
Teeter: Typically, larger college and university facilities have centralized chilled-water distribution systems. In most cases, colleges and universities prefer not to introduce VRF systems when centralized utilities are available. With VRF systems and the associated quantities of refrigerant, compliance with ASHRAE 15: Safety Standard for Refrigeration Systems and Designation and Classification of Refrigerants can complicate the overall design. Chilled beams can be implemented in facilities where ventilation requirements are lower and where the engineer can be confident that the building envelope will remain tight. Dew point measurement and control becomes critical when considering the use of chilled beams. With both VRF and chilled-beam systems, implementation of an outside-air processing system is a must.
Mosley: I have used chilled beams to serve laboratories that have a high sensible-heat gain. This helps to efficiently cool these spaces while greatly reducing the fan’s energy consumption and eliminate wasteful reheat energy.
CSE: What types of DOAS are owners and facility managers requesting to keep their facility air fresh?
Mosley: Many campus facilities staffs understand and embrace the use of DOAS systems to serve spaces in conjunction with radiant systems, such as chilled beams. This greatly reduces wasteful reheat energy and ensures the spaces are adequately and effectively ventilated with controlled air of the precise quantities needed at all times.
Teeter: In general, I have not had much experience with owners and facility managers specifically requesting dedicated outside air systems. In facilities with high outside-air loads, I think more often than not, the engineer is the one recommending these types of systems.
CSE: Energy efficiency and sustainability are frequent requests from building owners. What net zero energy and/or high-performance systems have you recently specified in college or university facilities (either an existing building or new construction)?
Mosley: I have been involved with several projects recently that have been striving to achieve net zero energy. The biggest challenge we always encounter is, firstly, getting the building energy-use intensity as low as possible. Then we focus on the available area for the PV system. In many cases, the shape of the building’s roof and self-shading become challenges when endeavoring to maximize the solar PV system output.
Laue: In energy-efficient, sustainable, net zero buildings, the mantra is “reduce then produce.” Whole-building energy-reduction strategies begin with massing and orientation, envelope design, incorporation of passive systems, design of active high-performance HVAC systems, high-efficiency lighting and electrical, and good building controls. Once the building has maxed out the potential for energy reduction, production strategies can be explored. The two we typically see are solar hot water and solar PVs. Both require a lifecycle analysis to determine financial feasibility. Grants, rebates, incentives, and funding sources should be studied.
CSE: What types of renewable or alternative energy systems have you recently specified to provide power for such projects? This may include photovoltaics, wind turbines, etc. Describe the challenges and solutions.
Laue: A remodel project at the University of Chicago, called the Keller Center at Harris Public Policy, will have 9% of the total building’s energy be provided by grant-funded rooftop PV panels, a system planned to expand to provide nearly 18.5% of building energy needs as funding becomes available. The challenge for this project was funding: Even though the system would pay for itself in a reasonable period, the university did not have the construction capital to include it. Grant money was secured to pay for the system.
Mosley: Fuel cells are being considered by universities. These present challenges for integration into the campus systems as well as other challenges due to their lifecycle-long payback. Therefore, power purchase agreements are favorable for these systems.
CSE: What are some of the challenges or issues when designing for water use in such facilities? What types of low-flow fixture, water reuse, or other techniques have you designed?
Laue: Facilities maintenance teams can be particular about the manufacturers and model numbers of plumbing fixtures used within their facilities. By having a standard product, they are better able to stock spare parts and replace damaged fixtures. Also, maintenance personnel are leery about being the first to try low-flow fixtures, particularly in existing buildings. Plumbing fixtures require a balance between water efficiency and a client’s interest in new technologies.