What unique heating or cooling systems have you specified into such projects? Describe a difficult climate in which you designed an HVAC system for a college or university project.
Tom Syvertsen: We’re seeing a lot of buildings requiring summer reheat paired with year-round specialty cooling spaces that require 24-hour operation as technology continues to grow. While not necessarily unique at this point, this is a good application for heat recovery chillers that are super-efficient when you have simultaneous heating and cooling loads. A small chiller sized for the summer reheat load or the winter 24-hour cooling load also allows the larger plant equipment to be off and not running at low capacity to satisfy these loads.
Randy C. Twedt: We designed an anatomy lab for a large university and specified chemical detection to convert the air handling unit from recirculation to 100% outside air depending on the chemical levels detected. This resulted in substantial energy reduction for the lab.
Kristie Tiller: HVAC system requirements are changing with the demand for increased energy efficiency. More and more, we are designing with variable refrigerant flow (VRF) systems. These dynamic systems have always been great for minor renovations, which we do a lot of at LAN. Recently, we’ve designed new construction projects with a full VRF HVAC system. This solution has a smaller, more flexible footprint than your larger chiller and air handling unit systems, is aesthetically pleasing to the owner and architect and has a greater energy efficiency than most systems.
Casimir Zalewski: This is a difficult question to answer. Working in multiple regions, we see each region asking us to incorporate different features to become more sustainable. So, what may be normal in one region may not be normal for another. For example, in Texas we have been requested to provide 18° or 20°F chilled water systems that require series cooling coils to improve central plant efficiency. These southern buildings also require specialized cooldown modes or continuous cooling operations to minimize central plant demand by having many buildings entering occupied mode simultaneously. In a cool climate, running a central system continuously through the night would be counter intuitive to save energy. By the same token, in colder climates, the use of condensing boilers with perimeter heat is common to minimize running central air handling systems during unoccupied cold night hours keeping energy usage down to a minimum, but such a practice would be rare in a hot southern climate. Similar issues appear with economizer types and functions, natural ventilation and building construction in general. Practicing in many regions and climate zones makes the designer question “what is unusual?” unusual.
For existing buildings, what HVAC, outdoor air, UV-C, bipolar ionization or other indoor air quality strategies are you designing?
Casimir Zalewski: Recently, I have seen an increase in the acceptance of dedicated outdoor air handling systems with specific focus on the flexibility on the amount of fresh air provided to each space. There is more of a desire to limit potential cross-contamination of filtered return air between spaces and occupants. Clients are more interested in limited recirculation between rooms. As part of system design, the question of in-room recirculation with respect to air turn over and filtration from central dedicated outside air is of more interest. Specifically, what are the terminal or zone level control equipment and what are their capabilities.
Tom Syvertsen: Our recommendations have typically stayed within the tested strategies of ASHRAE–specifically their recommendations from the Position Document on Infectious Aerosols.
What unusual or infrequently specified products or systems did you use to meet challenging heating or cooling needs?
Randy C. Twedt: A new product that we are using more frequently is a SMART glass technology. Halio smart tinting glass is responsive and reacts to sun on the building. SMART glass technology can dramatically reduce cooling loads to the space via actively adjusting and minimizing solar heat gain through the windows.
Casimir Zalewski: Recently, I have seen an increase in the use of decoupled ventilation and heating and cooling systems. I wouldn’t classify variable flow refrigerant or chilled beam/radiant heating systems unusual, but there has been an increase in the use and application of decoupled systems to address heating and cooling needs.
How have you worked with HVAC system or equipment design to increase a building’s energy efficiency?
Patrick McCafferty: It’s important to remember that the COVID prevention upgrades outlined in ASHRAE’s April guidance document are aimed at fighting a pandemic. These are not the new gold standard in HVAC design. If we fail to make this distinction, we run the risk of overdesigning all our future buildings, which would be unnecessary, expensive and counterproductive to our long-term energy goals. After all, the success of any business depends not just on surviving the COVID crisis, but on building lasting resilience — and a key part of building overall resilience is continuing our commitment to creating more sustainable, energy-efficient buildings to help combat climate change.
Tom Syvertsen: Recovering energy every logical place you can, paired with identifying and maximizing opportunities for “free cooling” or “free heating” based on equipment selection or operations help optimize the design and reduce both energy usage and carbon footprint.
Randy C. Twedt: Often for networks of university lab buildings, we design complex control systems that allow the buildings to perform at maximum efficiency. For example, the integration of the exhaust hoods and HVAC systems in the buildings is important to allow the systems to ramp up and ramp down depending upon occupancy, which increases efficiency while reducing costs. It is also important for users to have the flexibility to modify their environments when they are occupied.
Casimir Zalewski: HVAC systems and equipment are required to meet some peak system demand determined by the project’s need, municipal codes and standards or industry guidelines and standards. While there are requirements for part load performance, much of the actual performance is based on how the building operates most of the time. Most buildings are not operating at peak loads most of the time, so how the system and equipment transition and operate between peak and more often between varying part loads will determine the buildings’ overall efficiency. We strive to understand transitions and define differing part load values to provide temperature control sequences, including resets, time delays, deadlands and staging guidelines, to system programmers to maximize energy efficiency. We are also seeing more acceptance comparative energy trending to benchmark system performance and flag deviations.
What best practices should be followed to ensure an efficient HVAC system is designed for this kind of building?
Casimir Zalewski: We strive to understand transitions and define differing part load values to provide temperature control sequences including resets, time delays, deadlands and staging guidelines to system programmers to maximize energy efficiency. We are also seeing more acceptance comparative energy trending to benchmark system performance and flag deviations.
Tom Syvertsen: Perform an LCCA at the onset of a project to compare different systems and select the one that is the most efficient. Use energy recovery systems to the fullest extent practical. Ensure all systems have adequate turndown to avoid wasting energy during the majority of the year when heating and cooling loads are not near peak. Work with the architectural team to achieve the most energy-efficient envelope the project can afford. The best way to save energy is to not need as much of it in the first place.
Randy C. Twedt: As an integrated A/E firm, our design approach combines BIM and Building Performance Analysis results to “remodel things less,” better capitalize on our architecture and engineering practices, proactively communicate performance opportunities and inform a data-driven approach to design. HVAC systems can no longer be designed without regards to other disciplines. Involving cross-discipline efficiency measures is critical to ensure all sustainable design features are working synergistically.
What unique HVAC systems have you specified for campus dorms? How do you help engage and educate the students with this design?
Tom Syvertsen: We have implemented window sensors that shut off the heating/cooling (for example, a 4-pipe fan coil unit) in a dorm room when the window is opened. This avoids wasted energy and other unintended issues that could be caused by bringing warm/moist outdoor air into the building while the cooling system is operating. This provides a practical example to students about energy usage and promoting a healthy building environment.
What is the most challenging thing when designing HVAC systems in such buildings?
Randy C. Twedt: Space allocation is a constant challenge. There is often tension between the design team, seeking the highest ceilings possible and the contract, looking to reduce costs. Routing the HVAC systems is often the element that suffers due to the dynamic.
Kristie Tiller: College/university buildings are built to have a long life span and the spaces within these buildings often change function throughout the years. The challenge lies in maintaining proper space conditions throughout the evolution of each space. This can be accomplished through well planned initial design and well thought out renovation down the road. During initial design, we must ensure that we are tying into existing plants properly while also balancing overall economics from an energy use and long-term maintenance standpoint. University buildings are built to last decades and must be properly maintained to protect the integrity of its systems. The HVAC challenge is to design an effective, efficient, flexible and easily maintained system that meets university guidelines and ties easily into existing systems.
Tom Syvertsen: Keeping it simple. A building with unusual or complicated equipment, interconnected systems and complex sequences for controls may be extremely energy efficient, but it needs to be workable to the owner. If they cannot understand or maintain the systems, then there is a good chance they may disable energy-saving features or bypass some of the technology. It’s a fine line to walk–systems that are super-efficient on paper do not actually save any energy if they are not ultimately used.
Casimir Zalewski: Maximizing energy efficiency in buildings typically requires facility personnel to accept either a system or equipment they are not as familiar or comfortable with, modes of operation that are different or more sophisticated controls and monitoring. In any of these cases, reaching an understanding with the many groups on how this building may act or operate differently can be challenging. For example, traditional gas fired boilers or chillers operated most efficiently when fully loaded. With the widespread acceptance of condensing boilers and variable speed chillers, these systems typically operate best at part load. Running the condensing boilers or variable speed chillers the way the traditional systems operated will reduce system efficiency and negatively impact the investment. So, the challenge is not in just the design and construction of such buildings, but the programming and ultimately how the building systems are being operated.