Focus on specialty structures: HVAC and plumbing
Wayne E. Allred, PE, LEED AP
Allred brings 30 years of electrical engineering experience to his position as Principal and Regional Director of the company’s Orlando unit. His career choice was inspired by growing up on Florida’s space coast, watching Saturn V rocket launches and other events.
Scott Foster, PE, LEED AP
Foster joined AEI in 2007 and now serves as managing principal. He was a 2016 Consulting-Specifying Engineer 40 Under 40 award winner.
Kevin Lewis, PE, LEED AP BD+C
Senior Vice President/Venue Practice Director
As Senior Vice President/Venue Practice Director, Lewis has managed the design of more than a dozen LEED-certified sports projects. Before joining the company, he received collegiate scholarships for baseball and track.
Robert V. Hedman, PE, LEED AP BD+C, WELL AP, Fitwel Amb.
As principal, Hedman serves as co-head of the mechanical department, oversees staff and managers numerous large projects. He focuses on coordination between disciplines and systems integration with architectural and structural design components.
CSE: What unique heating or cooling systems have you specified into such projects?
Foster: The upper Midwest experiences many hot humid days as well as many that are subzero. Such systems as in-floor radiant heating and cooling, ceiling fans and variable air volume chilled beams help meet the demands of both conditions. Systems that allow for reduced outside air help reduce the impact of the extreme design conditions.
Lewis: We are seeing a lot of venues located in difficult climates that want to take advantage of outdoor/indoor spaces. We have been innovative in how we handle these situations and really try to take advantage of new concepts that allow the patrons to be comfortable, but yet still enjoy being outside and close to the action.
Hedman: Our projects located in New York City use utilities with rates that are generally the highest in the nation. Generating and storing ice using thermal energy storage systems allows chillers to operate during off-peak hours when utility rates are significantly lower. Shifting energy demand to off-peak hours reduces the electric demand rate and cost. Another benefit of thermal ice storage is the chiller plant can be reduced by up to 30% to 50%.
CSE: What unusual or infrequently specified products or systems did you use to meet challenging heating or cooling needs?
Foster: The VAV chilled beams used on Northwestern’s Ryan Walter Athletics Center were a unique product, the Adapt Parasol by Swegon. Chilled beams are often provided with constant air volume that can require reheat to avoid subcooling spaces. This VAV system allowed for reheat to be removed while still maintaining space temperatures.
CSE: How have you worked with HVAC system or equipment design to increase a building’s energy efficiency?
Lewis: We focus on load reduction first, energy efficiency second and then turn our attention to renewable energy sources. Tackling the building in this order has been successful and led to several LEED certified projects that have been above and beyond the local energy codes.
Foster: Overall HVAC system selection is key to energy efficiency with regards to mechanical systems. Traditional all-air systems, involving large air handling units with large fans, use a lot of fan energy. At times, this is the most cost-effective upfront approach, but more passive radiant hydronic systems can have a significant energy savings for a slightly higher capital cost. Geo-exchange systems are also a good system choice to reduce energy use.
CSE: What best practices should be followed to ensure an efficient HVAC system is designed for this kind of project?
Foster: It is the responsibility of the engineer to gain the best understanding from the building owner on how he or she intends to actually use the spaces within the building. HVAC design is based on a lot of assumptions, from load calculations to occupancy scheduling. While we cannot predict the future, the more we can match those assumptions to the intended reality, the better a system functions and meets the building’s needs.
CSE: What is the most challenging thing when designing HVAC systems in such buildings?
Allred: We currently have a performing arts center in construction. The acoustical hall has been designed to achieve N1 sound rating. The sound requirement required close interaction between the architect, mechanical engineer and acoustician on the project. Challenges included the acoustic joints with ductwork, which was required to be insulated for sound and required to be fire rated to meet the rating of the penetration. The hall also includes a moveable cassette (four-story structure for adaptable stage configurations), which required an umbilical ductwork connection to provide comfort cooling during performances. Current design trends have included architecturally expressing the structure in performance spaces. This has limited where ductwork can be routed in an agreeable fashion and at times has required the ductwork to be exposed and a feature of the overall design.
Foster: A common struggle for engineers when planning out for mechanical systems is finding space for large air handling units, fans and duct systems in mechanical rooms. Mechanical rooms must be sized large enough to not only house the equipment, but maintain access space for repairs, replacement and regular maintenance. Another challenge for HVAC engineers is designing efficient systems that meet the high cooling requirements of all-glass structures with significant solar heat gain. Engineers encourage architects to specify well insulated glazing systems or strategically place envelope openings, to maximize daylight while retaining the most energy possible within the building.
Lewis: The biggest HVAC challenge is changing the mindset on construction methods that have been in place for some time. To drive innovation requires new methods and techniques that haven’t always been used and that sometimes causes increased cost to cover the unknown. Working with the design and construction team collaboratively, we can devise innovative solutions that still work within the budget.
CSE: In historic structures, describe a project in which the plenum space or upgraded mechanical systems posed challenges.
Foster: Currently under renovation is the Abbott Hall Black Box Theater at Northwestern University, converting offices and catering/kitchen spaces into teaching theater spaces. The combination of large existing structural elements and new ones and limited floor–to–floor height was challenging to coordinate. Also, theaters require a lot of sound attenuation devices and intentionally oversized ductwork to eliminate noise. Located directly on the roof of the theater spaces, custom air handling units had to be specified with low noise fans and compressors. Coordination of the ceiling spaces of the theaters required special attention so the air distribution and fire protection systems didn’t clash with the lighting/theater track systems.