Engineering flexible office buildings

Office buildings need to have the ability to accommodate myriad types of businesses and activities to meet the needs of tenants. Here, engineers with experience on such buildings share their knowledge, lessons learned over the years, and emerging trends.

By Consulting-Specifying Engineer February 14, 2017

Respondents Cory J. Abramowicz, PE, HBDP, LEED AP, Associate, ESD (Environmental Systems Design), Chicago.

Matt Chandler, PE, LEED AP BD+C, BEAP, Senior Engineer, KJWW Engineering Consultants, St. Louis.

Andrew B. Horning, MS, LEED AP BD+C, Associate & Project Manager, Bala Consulting Engineers Inc., King of Prussia, Pa.

Julianne Laue, PE, LEED AP, BEAP, BEMP, Senior Energy Engineer, Mortenson Construction, Minneapolis.

Matthew Pastore, CxA, Director of Design-Build Services, GHT Ltd., Arlington, Va.

John Yoon, PE, LEED AP, Lead Electrical Engineer, McGuire Engineers Inc., Chicago.

Mike Walters, PE, LEED AP, Campus Energy Market Leader, MEP Associates LLC, St. Paul, Minn.

CSE: What’s the No. 1 trend you see today in the design of office buildings?

Cory Abramowicz: The biggest trend in the market we’ve seen lately is increased monitoring and measurement of energy within the building. This includes adding more meters to submeter chilled water, hot water, electricity, domestic hot water, and outside air because building owners want the flexibility to include or not include services in the tenant leases-and use these services to market to potential tenants. Additionally, tenants want more amenities, such as access to fitness centers, additional conference spaces, and a diverse mix of retail shops and/or restaurants located within the building. They’re also increasingly interested in knowing not only how much cooling, heating, and electricity they’re using, but also how these services are being distributed. Companies are seeking more sustainable methods to fulfill sustainability initiatives, which is where high-end and flexible controls, technology, and modern systems play a big part.

Matt Chandler: There is increasing awareness of integrating building design with occupant well-being. For example, locating the stairs to be equally convenient and accessible as the elevators promotes stairs use. Another example is moving the majority of the built spaces to the interior of the building and including clerestories so more occupants have access to natural daylighting.

Andrew B. Horning: I’ve noticed increased flexibility for collaboration.

Julianne Laue: Our clients are asking for building designs that help attract and retain quality team members. They are looking for buildings that inspire health and wellness, are full of natural light, and are flexible and adaptable for future needs.

Mike Walters: A considered move to low-entropy/near-room temperature heating (~120°F) and cooling (~60° F) systems. This is often in the context of district energy or campus-type settings to drive the lowest possible energy use. From a system perspective, this is often reflected as chilled-beam systems, variable refrigerant flow (VRF) applications, or even standard variable air volume (VAV) systems with larger air handling unit (AHU) coils.

John Yoon: In multitenant office buildings, we’re seeing more emphasis on providing in-house amenities (shared conferencing facilities, fitness centers, Wi-Fi lounges, "party decks," pop-up restaurants, etc.). What’s unusual about this is we’re seeing building owners providing these amenities for buildings located in central business districts of large metropolitan areas. You would expect that the inherent advantages of being in these types of locations-being in the middle of everything-would make these types of amenities redundant. However, there is a pervasive fear among building owners that if such amenities aren’t provided, they’ll be left behind in the competition for new tenants or even in retaining existing ones. It’s unclear if this trend is sustainable. Constructing, and more important, operating and maintaining these facilities does severely impact a building’s financial bottom line. It may ultimately be nothing more than a passing trend, like the outlandish employee fringe benefits that characterized tech companies in the dot-com era. Only time will tell.

CSE: What other trends should engineers be aware of for such facilities in the near future (1 to 3 years)?

Laue: Engineers should be ready to be "optioneers,"and provide a range of options that look at comfort, reliability, controllability, energy efficiency, first cost, and code compliance. These options will need to be laid out so the owners fully understand the overall impacts they can expect.

Yoon: With the growth of the distributed-generation market, decreasing overall demand, and stagnant electricity rates, we expect to see major efforts by utility companies in pushing for massive overhauls of electricity-rate structures. In this current deregulated environment, most traditional utility companies seem to be struggling with finding new revenue streams so that they can meet the expectations of their shareholders. In an odd twist, many states are forcing their regulated utility companies to enact consumer energy efficiency programs, which if successful, can only further reduce revenue for the utilities. The "answer" that many regulated utility companies are embracing is shifting from usage kilowatt-hour-based rates to demand kilowatt-based rates. The primary argument by utilities is that demand-based rates more accurately reflect the true cost of delivering electricity. With the deployment of smart meters, such rates changes are now more technically feasible. The only hurdle is legislative, and there is a significant lobbying effort in many statehouses to make this happen. So why does a change in electrical utility-rate structures matter? The two greatest costs for most office building owners are taxes and utilities. The prevailing expectation is that demand-based rates will significantly increase utility costs for most buildings. Taking this into consideration, simple energy efficiency considerations in base building mechanical, electrical, and plumbing (MEP) system design isn’t enough if rate structures do change. MEP design will eventually also have to address maximum concurrent demand, "capacity factor," and other seemingly foreign concepts.

Horning: Engineers should be aware of a less-built environment with accessibility to informal meeting spaces-i.e., bench-style workstations with huddle/scrum/war rooms for four to 10 people and modular furniture and wiring kits of parts to address office-space churn.

Chandler: Many of the current and future trends include evolving technologies, such as electronic room-scheduling displays outside of shared conference spaces. These room schedulers integrate with the scheduling software used by the occupants and display real-time information on stationary and portable electronic devices, eliminating the need for daily updates of posted paper schedules. New wireless audio/video (AV) technologies also are becoming more prevalent, potentially reducing the need for fixed inputs in the floors or walls. In addition, video/media walls and digital displays are growing trends. Open offices with shared conference space promote a collaborative environment, and we are seeing an increased use of furniture solutions and demountable partitions in lieu of fixed construction as well as interior offices and clerestory windows to promote access to daylight.

CSE: Please describe a recent office building project you’ve worked on-share details about the project including location, systems engineered, team involved, etc.

Chandler: We provided the mechanical, electrical, and technology design on a 500,000-sq-ft office building currently under construction in St. Louis. The building is comprised of 12 stories of office space, a lower level for parking, storage, and utility spaces, and includes a bookstore, café, and public safety center. Systems include campus chilled water, high-efficiency boilers for hot-water heat, a dedicated outside-air unit, an AHU per floor, VAV boxes and fan-terminal units for zone-level control, LED lighting, daylight dimming controls, a voice-evacuation fire alarm system, and an emergency generator for life safety and optional standby loads.

Laue: Kohl’s Innovation Center in Menomonee Falls, Wis. The team included Mortenson as the construction manager and MulvannyG2 Architecture as the architect. Ring & Duchateau was the commissioning authority (CxA) and Hargis Engineers performed monitoring and evaluation of the basis of design. The Kohl’s Innovation Center transformed an existing 300,000-sq-ft manufacturing building into a new corporate office space for more than 1,650 employees. The building’s open concept features modular cube-type workstations, collaborative spaces, and five mezzanines containing offices, conference rooms, elevators, and restrooms. The facility also features a full-service kitchen, servery, and an auditorium with seating for 1,500 people. Sustainable features include five clerestory assemblies and large windows for interior daylighting, low-flow plumbing fixtures, LED lighting and underfloor air-distribution (UFAD) HVAC systems with a high-efficiency heating and cooling plant, trash/recycling stations, three solar trees, and plug-in electric vehicle charging stations.

Horning: We recently engineered the 240,000-sq-ft fit-out for FMC Corp., a large chemical and products company, across 11 floors of a 49-story mixed-use development in Center City, Philadelphia. Our firm was the core and shell and tenant MEP/fire protection (MEP/FP) engineer for the project. The base mechanical system consisted of floor-by-floor water-cooled VAV systems. FMC was moving out of legacy space with enclosed perimeter offices. Working with FMC and granum A/I as project architect, the mission of the project was to create an open, flexible, state-of-the-art workspace. We used HVAC and lighting zoning to provide office neighborhoods by department, as well as provided flexible meeting spaces and heads-down work areas. The charge from the design team was to protect the window wall, so there were no perimeter offices in the typical workplace. All hard- and soft-walled offices were interior spaces, and we designed our perimeter zoning to handle the exterior skin loads. In addition to the typical workplace and executive space, we also had the challenge of putting a full-service cafeteria and kitchen on the 25th floor of a 49-story high-rise, including designing kitchen exhaust with a rated grease duct to the high roof. Plus, we designed standby power to selected tenant areas from a lower-level diesel generator.

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

Horning: Both the core and shell and tenant projects were designed in Revit. Our design team participated with the architectural teams, the construction manager’s BIM coordination team, as well as subcontractors to build a federated model by floor to maximize coordination. We found this method to be highly successful and productive for the whole team. Chandler: On a recent project employing a design-assist approach, the contractors were brought on board early in the design process and worked in conjunction with the design team to create the BIM used for coordination and construction. We used a collaborative method in which we remained the engineer of record while using the contractor’s fabrication and construction model for final coordination and documentation. The information was provided just in time, with building construction starting as the shell and core model was completed and fit-out construction following as the fit-out design was completed. The model was used throughout design and construction to coordinate between trades and to communicate with the owner. The contractors and the design team held multiple weekly and biweekly meetings during the process to incorporate cost-saving techniques, maintenance-friendly designs, and time-saving installations without sacrificing the integrity of the building.

Yoon: The concept of BIM is still relatively nebulous for many office building owners. They say they want it, but they aren’t entirely sure what they are asking for. Once they get a final work product, they aren’t sure what they should do with it. In such cases, defining and managing those expectations is our primary challenge. Something as simple as explaining the concept of the level of detail is incredibly useful for these types of clients. For projects where energy modeling is part of the scope of work, having accurate and complete BIM becomes critical. However, the architect’s focus during creation of the BIM often doesn’t align with our energy modelers’ requirements. What should be straightforward tasks, such as exporting geometry data from a model, can become coordination nightmares. Gerber file extension exports end up becoming "all-or-nothing" affairs, with a handful of small and seemingly inconsequential architectural errors in the model bringing the entire process to a grinding halt.

CSE: Have you designed any such projects using the integrated project delivery (IPD) method? If so, describe one.

Chandler: One of our recent projects was similar to IPD, bringing the construction manager and subcontractors onboard early in the process for construction analysis, cost estimating, and model development. The design team was the engineer of record and the contractor’s construction model was used to create the final construction documents. There was extensive and ongoing coordination between the design team, construction team, and owner throughout the design and construction phases.

CSE: Describe the commissioning, recommissioning, or retro-commissioning process for an office building project. At what point was your team brought in, and what changes or suggestions were you able to implement via commissioning?

Yoon: In our experience, commissioning projects for new construction have typically been relatively straightforward. On the other hand, it seems no two retro-commissioning projects are ever the same. The dynamic nature of these projects keeps you on your toes. In older facilities, simple tasks can be an incredible challenge-like trying to determine how the original basis of design has been modified over the years with subsequent system modifications. What many CxAs seem to lose sight of in these situations is that the process has to be a shared experience of discovery and education between the CxA and the building operations staff. We’ve been in numerous situations where the operations staff has complained about previous CxAs dictating changes without properly addressing concerns with the operations staff. Another major complaint was that there was often no follow-up to ensure that the recommendations were effective. While in some cases the CxA’s analysis and recommendations may have been valid, when a building’s chief engineer feels that his or her opinions have been slighted or the recommendations are not properly explained, it’s not uncommon for the operation of the building systems to mysteriously revert back to their previous state after a few months.

CSE: Have you designed an office building as part of a "smart city?" If so, describe the project.

Walters: As part of a major campus-revitalization project, we designed a large geothermal heating and cooling system to provide a highly efficient central chilled and hot-water supply system to a cluster of office buildings. The project is currently under various stages of design and construction. The office buildings use a low-temperature chilled-water system (42°F) for dehumidification and cool-water system (approximately 60°F) for chilled beams supplying comfort cooling. Heat-recovery chillers are used in conjunction with thermal-energy storage tanks (hot and chilled water) to provide the central heating and cooling.