Best practices for designing HVAC systems in government buildings
Learn how to specify HVAC systems for government and military buildings
- Chris Ankeny, PE, LC, LEED AP BD+C, Associate/Senior Electrical Engineer, Clark Nexsen, Virginia Beach, Va.
- Mark Chrisman, PhD, PE, Health Care Practice Director/Vice President, Henderson Engineers, Kansas City, Mo.
- Randall Ehret, PE, Technical Director | Electrical, ESD, Chicago
- Todd Garing, PE, LEED AP BD+C, Vice President, Mueller Associates Inc., Linthicum, Md.
- Rob Jordan, PE, FPE, LEED AP, Mechanical Department Manager, Burns & McDonnell, Kansas City,
- Julene May, PE, PMP, Chief, F-35 Beddown Program Management Office, Stanley Consultants Inc., Eielson AFB, Alaska
- Jon Sajdak, PE, Associate Fire Protection Engineer, Page, Austin, Tex.
- Troy Windom, Automation Manager, Dewberry, Raleigh, N.C.
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 government, state, federal, correctional and military project.
Rob Jordan: Burns & McDonnell has designed unique preconditioned air systems for several military aviation projects. A preconditioned air system allows for pumping cooling air directly to the aircraft inside a maintenance hangar. These systems are typically required for cooling the avionics systems in the aircraft during testing procedures and need to provide air at 35-40 degrees Fahrenheit at a pressure of 5 psig to any or all of the aircraft as quickly as 30 minutes after the system has been activated.
We recently completed the design for MEP systems for a passenger terminal and air traffic control tower for the U.S. Army Garrison at Kwajalein Atoll, located in the Marshall Islands. Kwajalein’s climate is considered one of the most corrosive marine atmospheric environments in the world, which presented a unique challenge on this project. Our goal was to deliver facilities designed to a minimum life of 50 years.
Chris Ankeny: For two enlisted dining facilities on the Marine Corps Base Camp Pendleton, California, NAVFAC Southwest’s design requirements were studied closely. The sunny and arid climate of southern California informed the engineering solutions for the projects. Through the use of efficient HVAC equipment, a highly-performing envelope, low-energy lighting and extensive on-site PV panels, these LEED Gold certified buildings achieve a 34% cost savings over the baseline ASHRAE model. The HVAC systems and the interior/exterior lighting systems are modified by specific building automation systems (BAS) controls that respond in real time to daylight levels, environment temperature levels and occupancy.
What unusual or infrequently specified products or systems did you use to meet challenging heating or cooling needs?
Chris Ankeny: A unique mechanical system for Davis Barracks included radiant floor heating and cooling slab systems; a first on the West Point campus. The systems are controlled by a direct digital control (DDC) building management system (BMS), which includes window open/closed sensors to ensure temperatures and humidity are monitored and adjusted within narrow tolerances to optimize radiant system performance.
We have used geothermal pump systems for a handful of projects where the conditions related to site and building load were favorable.
How have you worked with HVAC system or equipment design to increase a building’s energy efficiency?
Chris Ankeny: HVAC systems that are designed to increase building energy efficiency incorporate elements including exhaust air energy recovery, variable speed pump and fan motors. We are always looking for opportunities to recover energy and water.
Rob Jordan: In accordance with UFC 1-200-01, Burns & McDonnell performs a complete building energy model and life cycle cost analysis of multiple HVAC systems. This allows comparison of the systems to select the cooling or heating system that will provide the lowest overall 40-year cost. These steps in the design process happen before the 35% submittal and show that we have reviewed multiple system options and equipment efficiencies to achieve an energy efficient building that fits the needs of each unique facility and its users.
What best practices should be followed to ensure an efficient HVAC system is designed for this kind of project?
Chris Ankeny: Overall, energy modeling combined with life cycle cost analysis leads to the most efficient HVAC system for the project. DOD projects also include energy mandates that must be complied with to help each branch achieve its goals for energy efficient buildings.
What is the most challenging thing when designing HVAC systems in such buildings?
Randall Ehret: One of the most challenging mechanical aspects for the McCormick Place COVID Alternative Care Facility was using the existing air handling units serving the exhibition halls. These halls are served by a number of constant volume, variable temperature air handling units, sized to handle convention loads consisting of large groups of people, heat generating equipment and large volumes of outside air at peak design conditions. These units do not have the ability to reduce the volume of supply air to match the significantly reduced loading now required for the Alternative Treatment Center and maintain proper space and humidity temperatures. In addition, the operating criteria for the facility required the maximum amount of outside air with minimal recirculation back to the space. This was an additional challenge as heating and cooling coils are sized based on minimum code required outside air. To overcome this situation, we calculated the maximum amount of outside air that could be brought into the space based on outside air conditions and developed a spreadsheet for the authorities use so they could adjust the amount of outside air to each air handling unit thus providing the maximum amount of air changes to the spaces each hour.
Rob Jordan: Each federal, government or military facility has unique challenges in terms of climate, user system preferences, installation design guidelines, facility-specific Unified Facilities Criteria requirements and security requirements. One of the biggest challenges is evaluating the various system and equipment options that are available to meet all pertinent requirements of the facility, then analyzing and determining the best system for the facility given its unique needs.
Chris Ankeny: The cost of HVAC is challenging. Regardless of building orientation and the amount of glazing, the capabilities and limitations of the specified HVAC system will have the biggest impact on the facility’s energy performance. I would also mention an important aspect for DOD projects is knowledge of numerous UFC (unified facilities criteria) documents to ensure compliance with all requirements.