Class A office building system design

Class A office buildings are among the toughest projects an engineer can work on—complex structures, demanding clients, and advanced technology.

By Consulting-Specifying Engineer February 24, 2016


Daniel G. Dowell, VP Energy Performance Contracting Sales, ABM, Raleigh-Durham, N.C.

Kurt Karnatz, PE, CEM, HBDP, HFDP, LEED AP, President, ESD, Chicago

Lance Kempf, PE, Director of Mechanical and Electrical Engineering, LEO A DALY, Minneapolis

Brian Michelson, PE, MEP Design Phase Manager, Mortenson Construction, Minneapolis

Joseph H. Talbert, PE, ARM, Project Manager, Aon Fire Protection Engineering, Lincolnshire, Ill. 

CSE: Please describe a recent Class A office building project you’ve worked on—share details about the project including building location, building type, team involved, etc.

Lance Kempf: LEO A DALY was commissioned by the SAC Federal Credit Union, Nebraska’s largest credit union, to assist with site selection and provide master planning, programming, complete architecture and engineering services, and contract administration services for its new corporate headquarters campus in Papillion, Neb. The design for the headquarters reflects SAC’s close culture, collaborative work environment, and commitment to the community. The headquarters rests on a strong brick foundation, a metaphorical representation of SAC’s member-owner base. We were tasked with creating a collaborative, energetic, and forward-thinking headquarters that accommodates SAC’s growth and also reflects its unique standing as a leader in the business community. The new 94,000-sq-ft, four-story headquarters houses as many as 250 employees, enabling the consolidation of all corporate departments including operations, human resources, marketing, lending, finance, quality assurance/compliance, and information technology. The facility includes a branch credit union with both drive-up and external ATM options, and staff amenities consisting of a lounge with food service, a health and fitness center, and a community room. The ground-breaking was in 2012, and the facility opened in May 2014.

Kurt Karnatz: We recently completed a 25-story, 950,000-sq-ft multitenant office tower for Al Hilal Bank in Abu Dhabi, United Arab Emirates. The all-glass building envelope with high floor-to-floor heights presented a unique challenge in developing effective and sustainable engineered solutions while meeting energy code and Estidama requirements (a building performance rating system). Functionally, the goal was to create highly flexible lighting, power, fire protection, and cooling systems that could support multiple tenant configurations and loads. To achieve this, we created a modular ceiling and floor grid that does not require modification to support multiple configurations.

Brian Michelson: This project was designed and constructed before I started working at Mortenson. Located in downtown Minneapolis, it involved turning a vacated 90,000-sq-ft, four-story department store into offices for Centerpoint Energy. The building is located at a light rail stop at the intersection with Nicollett Avenue. RJM Construction was the general contractor and HGA was the architectural firm. The HVAC was design-build by Egan Co. The electrical design-build portion was by Muska Electric. The project was designed and constructed with the goal of achieving U.S. Green Building Council LEED Silver CI.

Joseph H. Talbert: Aon Fire Protection Engineering (Aon FPE) is involved in many projects for Class A office buildings, both new projects and renovation of buildings. One recent project involved a high-rise office in Europe working with U.S. and European architects. Another project a few years ago was a high-rise office building in Seoul, South Korea, involving U.S. and Korean architects.

CSE: What business development techniques are you using to gain Class A office building clients and/or projects?

Karnatz: We channel our business development activities around our ability to demonstrate empirical proof that our approach to analytics, development of solutions, integrated design, and implementation creates measurable competitive advantage for our clients. We demonstrate this through understanding our clients’ enterprise goals and business drivers and then developing solutions that achieve their desired economic, environmental, and experiential outcome targets.

Joseph H. Talbert: Over the years, Aon Fire Protection Engineering (Aon FPE, and its predecessor organization Schirmer Engineering) developed long-term relationships with architects such as Skidmore, Owings & Merrill, Gensler, smdp, and Smith+Gill, to name a few. By establishing these relationships, Aon FPE has become the firm that these architects turn to when they have a need for fire and life safety expertise for high-rise and supertall high-rise buildings.

CSE: How have the characteristics of Class A office building projects changed in recent years, and what should engineers expect to see in the near future (1 to 3 years)?

Talbert: The characteristics of Class A office buildings have changed significantly over the past 4 decades. Forty years ago, the Willis Tower (then the Sears Tower) was an anomaly because it was a fully sprinklered building. Now, a Class A office building without sprinklers would be an anomaly. In addition, the electrical communications capabilities of Class A offices from as little as 20 years ago would be undesirable in new Class A office buildings now.

Michelson: Projects are trending to more mixed-use with retail space, restaurant, and residential occupancies included in the total project. The future will probably see more building owners looking for exit strategies that would allow for resale within 5 years of construction completion. Building owners also are looking for ways to have tenants pay for improvements and utilities consumed. This moves HVAC system selection toward components that make that easier. Central chiller and boiler plants are the backbone of a water source heat pump system and are used when most of the building will be leased to multiple tenants. BIM has now reached the point where it is required by owners and general contractors, and not just because that is what the architect is using. Mechanical, electrical, and plumbing (MEP) design/build contractors are embracing BIM and are investing the time and resources to make it work.

Karnatz: The general notion or definition of a Class A office building has both subjective and continuously evolving components. There are basic givens or prerequisite requirements for power, cooling, flexibility, amenities, etc., that are necessary to satisfy both the current and future needs of the occupants. We are focused on creating highly integrated and symbiotic buildings that are authentic and empower and facilitate the occupant through awareness and control. As engineers, we need to understand how to leverage rapidly developing and maturing technologies, edge-device logic, the so-called Internet of Things, and analytics to create buildings that are predictive, responsive, adaptive, diagnostic, and self-healing. Advances in the application of technology in building systems along with increasing expectations and demands of building occupants make the coming years incredibly exciting for engineers in building design.

CSE: On what aspect of Class A office building projects do you see the most emphasis being placed by building owners? In what areas is your firm doing the most engineering work?

Michelson: In addition to first costs, energy and operating costs seem to be driving most building-owner concerns. More time is spent in energy modeling along with increasing HVAC-zone sizes to improve energy efficiency while reducing initial first cost.

Talbert: All aspects of fire and life safety features are being given great emphasis today, especially automatic sprinklers, fire-detection and alarm systems, and protection of means of egress. In addition, to allow architects greater design freedom for new Class A office buildings, performance-based design (PBD) is often used to provide adequate fire safety for special building features such as tall atria, which would not be allowed by strict compliance with the building code.

CSE: Describe your experience working with the contractor, architect, owner, or other team members in creating a BIM model for a Class A office building project.

Talbert: BIM models are becoming the standard for design of new Class A office buildings. On one recent project, the BIM files were not sufficiently complete to describe an atrium. The BIM files had to be completed to a greater degree to allow the use of computation fluid dynamics fire modeling to analyze the smoke control requirements. This is a common issue because the fire and life safety requirements for PBD designs must frequently be developed early in the design process.

CSE: Describe a recent retrofit of a Class A office building (or the updates to make the building into a Class A facility). What were the challenges and solutions?

Karnatz: We recently finished a complete HVAC, lighting, and plumbing retrofit of a 1.4-million-sq-ft office building in Chicago. Throughout the construction process, the 30-story building remained fully occupied with the exception of three "swing floors." Working in an occupied building added considerable cost to the project, but was necessary to maintain the desired tenants. Using a highly integrated BIM process, and integrated project delivery approach, we worked closely with the owner and contractors to establish existing-condition baseline models that were then used to model retrofit options and analyze options costs, savings, constructability, logistics, schedule, and return on investment. Creating detailed models allowed us to accurately analyze the implications and advantages of all options in making the best systems selections. This provided us the ability to focus on the greatest engineering challenge of the project—engineering the process of complete system replacement while maintaining occupancy and business continuity over the 4-year design/construction duration.

Talbert: If an existing building does not have sprinklers, smoke detectors, and smoke-control systems and is being retrofitted, it will probably require updated fire pumps and HVAC system modifications. If it was built before the Americans With Disabilities Act was adopted, substantial modifications to the fire alarm system will be required. These modifications may require total replacement of the fire alarm system.

Michelson: The challenges at the 90,000-sq-ft, four-story department store included re-use of existing air handling systems that also served as atrium smoke-exhaust systems; using chilled water and steam from a district energy plant, but the lines passed through an existing high-rise building; a small data center to be located on the first floor; an existing control system that was pneumatic and needed to be replaced by direct digital control (DDC) where practical; and the fact that the original department store had very few window openings on its two exposed exteriors and part of the project involved a three-fold increase in the number of exterior windows.

Our solutions: New exhaust fans were installed for the atrium and the air handling unit (AHU) controls were revised so they could provide make-up air when the atrium smoke-exhaust system was activated. The only concern for the chilled water and steam was that the owner of the connected high-rise submetered the steam to the new office space and would shut off the steam too early in the spring. The data center solution involved two AHUs served by chilled water that was available year-round from the district energy plant. Space was tight and the units were stacked one above the other. Most of the pneumatic control system was replaced by a DDC system. Some actuators and the steam-to-hot-water heat exchanger were left alone and are still pneumatically controlled. The original AHUs were sized for high-density people loads and high lighting loads. The current energy code requirements for lighting resulted in systems that were oversized, so the increase in windows did not require an increase in system capacity.