Designing higher education facilities: HVAC
The world is getting more high-tech, and the colleges and universities preparing students to work in an increasingly advanced environment must keep pace. HVAC systems, indoor air quality, and other related issues are discussed.
- David P. Callan, PE, Vice President, McGuire Engineering, Chicago
- Michael Chow, PE, CxA, LEED AP BD+C, Member/Owner, Metro CD Engineering, LLC Powell, Ohio
- Essi Najafi, FE, Principal, Global Engineering Solutions, Bethesda, Md.
- Mike Walters, PE, LEED AP, Principal, Confluenc, Madison, Wis.
CSE: What unique HVAC requirements do colleges and universities have that you wouldn't encounter on other structures?
Najafi: What makes the design of college and university buildings unique from an HVAC design perspective is the challenge of meeting the stringent energy code and LEED requirements of today while using the existing and often antiquated infrastructure. This infrastructure includes central campus steam boilers, dormitories originally designed to use natural ventilation, and roof structures that were not designed to hold rooftop equipment. Modern energy code requirements are pushing design engineers away from steam systems, while the campus engineers still desire centrally located heating and cooling equipment for maintenance purposes. Additionally, recent changes to the IECC requirements for building envelope construction and sealing have made use of natural ventilation difficult, if not impossible.
CSE: What updates in fans, variable frequency drives, and other related equipment have you experienced?
Najafi: In addition to the advent of the electrically commutated motor, traction has been gained in this industry for fan-array technology. Within the past 10 years fan-array driven air handling equipment has become commonplace in locations such as university hospital and laboratory spaces where redundancy is required, but there is not sufficient space to install two or more air handling units. The fan array allows maintenance to be performed on failed fan components while still providing HVAC services to critical spaces.
CSE: What indoor air quality (IAQ) challenges have you recently overcome?
Najafi: We were recently tasked to provide HVAC infrastructure for a new biosafety level (BSL)-2 laboratory that was installed in a space previously used as a locker room. The building in which this laboratory is to be constructed was originally built in 1975 as a public health building that included athletic, administrative, and locker room spaces. Our task as designers was to provide redundant air handling capability, variable air volume control, and energy recovery. The challenge with this design was the location. The laboratory was located on the ground floor, with an active gymnasium directly overhead and a small mechanical room located in the basement below. There was insufficient space in the mechanical room for redundant air handling equipment, so we provided a single (100% outdoor air) air handling unit with a fan-array air system and redundant cooling and heating coils. Variable air volume terminal supply and exhaust units were employed to minimize the waste of energy for this 100% outdoor air system. Additionally, redundant strobic fans were used to provide variable exhaust flow while maintaining exhaust air discharge velocity. To further reduce energy waste, a glycol run-around coil heat recovery system was installed in the exhaust and outdoor air ductwork.
CSE: In your experience, have alternative HVAC systems become more relevant?
Walters: I do think alternative HVAC strategies are increasingly becoming the norm. Some strategies-like chilled beams-are still difficult to advance through a design process with many constraints. I've found that demand control ventilation has very wide applicability (research labs, offices, variable occupancy academic environments, etc.) and offers a valuable mix of well-placed technology, simplicity, energy savings, and ventilation quality.
Najafi: Alternative HVAC systems are beginning to gain traction in the industry as their time in service increases and energy conservation requirements become stricter. In particular, we have seen a significant increase in the call for variable refrigerant volume (VRV or VRF) systems.
CSE: In densely packed dorms and student housing, how do you achieve optimal HVAC and air quality?
Najafi: Residence hall renovation projects can be extremely challenging. These spaces were designed for natural ventilation and have limited ceiling space for ductwork and piping. To circumvent this issue, we use a dedicated outdoor air system with corridor distribution to the living spaces. Heating and cooling (where required by the owner) is provided with chilled/hot water fan coil units or VRV units.