Engineering flexible office buildings: electrical/lighting/power and fire/life safety
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 regarding electrical/lighting/power and fire/life safety.
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: Describe a recent electrical/power system challenge you encountered when working on an office building.
Horning: One of our projects currently under construction is a 1.3-million-sq-ft tenant space that requires maximum flexibility. In their current location, this client churns approximately 1,000 workstations per year. To provide that level of future flexibility, we designed a modular wiring system with extended electrical tails to each floor box to provide an additional 15 ft of slack.
Chandler: On a recent project, KJWW presented the owner with options to circuit prewired office workstations. Providing each workstation with a dedicated circuit was costly, and circuiting more than four workstations to a single circuit presented the potential for nuisance tripping of the circuit breaker if high-current draw loads were plugged in, such as space heaters. KJWW presented real-world electrical demands for office workstations using a plug-in electrical meter. This gave the owner confidence to choose the four-workstation/circuit solution and inform users that space heaters would not be allowed.
Yoon: A significant percentage of our projects involve redevelopment/repositioning of existing buildings to use as office buildings. Oftentimes, the buildings are older and/or were used for entirely different functions (i.e., postal distribution centers, cold-storage buildings, industrial facilities, big-box retail stores, etc.). Surprisingly, many owners/developers prefer these types of redevelopment projects in lieu of new construction. While they still represent significant risk due to the presence of hidden conditions (asbestos, subsoil contamination, structural issues, etc.), the potential financial rewards often justify those risks. Many municipalities also offer significant tax breaks for redeveloping these properties, and that alone is often sufficient motivation. However, at the end of the day, the renovated building must be functionally equivalent to a new-construction building for it to be attractive to potential tenants. Ensuring that one of these buildings has sufficient electrical infrastructure to compete with newer Class A office properties can be a significant challenge. For example, imagine redeveloping a 40-story depression-era high-rise office building. Codes have changed dramatically since that building was constructed. Standard practices that were once commonplace-such as live front switchboards, electrical distribution equipment located in egress stairwells, cloth-insulated feeders, among numerous others items-usually necessitate wholesale replacement of that building’s electrical distribution system. Often, the new equipment doesn’t fit in the space occupied by the original equipment, requiring extensive coordination with the owner and architect to identify appropriate locations for new transformer vaults, switchboard rooms, electrical riser space, electrical closets, etc.
Abramowicz: As more building owners want to create additional submetering, a common issue that occurs is the existing electrical closet space within the building is inadequate. Additional submetering often requires additional equipment, and if the electrical closet was originally designed for only the current electrical system and its equipment, finding space for the new equipment without taking from tenant space is difficult. We’ve overcome this by working closely with the architect and owner to reserve undesired tenant space so that adding more submetering can justify the increased price per square foot sought out by the owner.
CSE: How do you work with the architect, owner, and other project team members so the electrical/power system are both flexible and sustainable at the same time?
Yoon: For every owner/developer that understands their vested interest in having a robust and flexible electrical distribution system, there are numerous others for whom these systems are an afterthought-or worse, they consider these systems to be nothing more than money spent on things that they will never see or care about. This isn’t intended to be a knock against owners. These viewpoints generally reflect a lack of understanding of how closely intertwined the electrical distribution system is with ensuring business continuity. Often, owners aren’t motivated to learn until some catastrophic electrical failure occurs. From a certain perspective, this could be considered a failure of the design community. One of the primary services that we should strive to offer is to provide adequate education to allow our clients to make informed decisions. The first step is to open a constructive dialogue early in the design process. While the task of formally documenting owner’s project requirements and basis of design may seem superfluous for some projects, the basic concept is that this level of communication between the owner and the design team can lead to an end product that better meets the needs of the client.
Abramowicz: Flexible workstations are becoming more common as people desire varied work settings depending on the tasks they’re working on or the people they’re working with. These workstations or conference rooms need enough power and connections to allow several users to plug in as necessary, yet be flexible if the users decide they need to reorganize the space. Sustainability can be gained from implementing user-cutoff switches to prevent plugged equipment from remaining on during periods of time the building is unoccupied. This eliminates the low-level power load demands generally seen from electronics such as TVs, computers, and appliances.
CSE: What types of smart grid or microgrid capabilities are owners demanding, and how have you served these needs? Are there any issues unique to these specialty projects?
Yoon: Microgrid applications are rare, with electrical rates in the Midwest at a record low. Unless there are other compelling reasons, such as business-continuity concerns, the rate of return typically doesn’t justify the initial investment. On the other hand, smart grids/smart meters are relatively pervasive due to local utility company initiatives. While the utility companies’ motivation for deploying smart meters may not necessarily align with the consumers’, more savvy clients realize that smart meters represent a valuable tool when trying to take advantage of the energy markets, whether it be a demand-response program or real-time/time-of-use pricing, all of which have the potential to significantly reduce operational expenses.
CSE: What lighting/lighting controls are in high demand for office buildings? Describe a recent lighting design project.
Horning: We’ve had great experiences using an integrated lighting control system design with wireless devices for ease of placement and relocation as needed. The backbone facilities maintenance functionality provided by these systems are attractive to larger tenants.
Abramowicz: Daylight harvesting is not new to the market; however, it is quickly becoming a staple among projects with sustainability goals and, in some states, code requirements. Due to the changing sustainability standards and certification requirements, daylighting is often the most economic option to meet certain certification levels, and according to industry studies, it has the added benefit of increasing occupant satisfaction. Also becoming popular are wireless sensors and control, which benefit both owners and tenants. For the owner, the technology allows the building to reuse the sensors or controls in a new tenant space if a former tenant moves out. The equipment can be reused in its existing location or relocated to an entirely different floor with minimal labor due to it being wireless. For the tenant, the wireless transmitters can be easily relocated within the space or on a desk, as these devices are battery-operated.
Chandler: LED fixtures have become the new norm for building lighting. With a wide variety of cost-competitive solutions, LED lighting is now the basis of design for all new projects and many renovation projects as well. For lighting controls, we are seeing a strong desire for simple, local controls in lieu of centralized lighting control systems. Light-level sensors to take advantage of daylight harvesting and occupancy/vacancy sensors are also typical for projects. The native ability of LED fixtures to provide dimming functions supports this transition to LED. However, because of the focused light output of the LED lamp, we have found it critical to review the size of the fixture, lens type, and lighting color temperature. LEDs can appear quite different from the fluorescent fixtures most people are accustomed to seeing in office spaces.
Yoon: One size doesn’t fit all for lighting controls. We specify everything from traditional relay panel-based systems to individual light fixtures networked together with wireless mesh controls reporting back via a gateway to server resident on the cloud. Ultimately, what gets specified is driven by budget, required functionality, and the client’s desire/tolerance for living on the bleeding edge of technology.
CSE: Describe a recent standby, emergency, or backup power system you designed, and its challenges and solutions.
Chandler: A recent office-building project is served by a triple-ended campus substation serving two double-ended building substations, of which each serves half of the building. A standby generator was provided for life safety systems and critical building functions, and a buildingwide uninterruptible power supply was provided for essential technology infrastructure. Implementing multiple levels of redundancy presented a challenge. The coordination of each system and sequencing was meticulously reviewed to confirm each level of redundancy was accurate. Space and location considerations for a standby generator and multiple transfer switches was also a challenge. The building site was very limited and the owner wanted the generator to be inside the building, so room design, intake and exhaust paths, and sound levels all needed to be addressed.
Horning: One recent challenge was providing backup power to a broadcast television station in a high-rise environment, to keep the broadcast tenant on the air 24/7. After a series of studies by our tenant and core/shell design teams, we were able to design a multiple-unit generator scheme to provide the standby power to the tenant’s systems, including their own standby chiller system, building condenser and domestic water systems, one cooling tower, and miscellaneous systems to keep the station on the air.
CSE: Are office building clients requesting addressable lighting systems? If so, describe the project.
Yoon: Infrequently. It is still unusual to have clients specifically request addressable lighting systems. Typically, when it is requested, that client already has an existing relationship with a particular vendor or manufacturer. Due to the proprietary nature of most lighting control systems, the request is generally intended to maintain a consistent standard across their facilities and avoid retraining/troubleshooting expenses associated with trying to support multiple different platforms.
Chandler: Power over Ethernet lighting and addressable lighting are being discussed early in the design process. The addressable lighting systems are relatively new systems that can greatly improve the energy efficiency of buildings. However, at this time, most owners are selecting traditional lighting systems due to the expense associated with the addressable lighting system.
CSE: What are some of the challenges for fire and life safety system design for office buildings? How have you overcome these challenges?
Abramowicz: Many modern office buildings incorporate architectural ceiling elements that are much more complicated than traditional, single-plane ceilings of the past. Whether in the lobbies or within the tenant spaces, ceiling designs often incorporate partial or complete exposed construction, floating-ceiling elements, open-grid ceilings, soffits, and many changes in elevations. Providing automatic sprinkler layouts that provide proper protection per NFPA 13: Standard for the Installation of Sprinkler Systems is more challenging with these types of ceiling designs. To overcome these challenges, more time has to be spent studying the architectural ceiling design to fully understand the implications. More coordination is needed with other disciplines when exposed construction design is incorporated. Most important, more effort is directed at reviewing sprinkler placement relative to the multitude of obstruction rules and other sprinkler-placement criteria found within NFPA 13. Additional communication is required with architects so they understand where sprinklers need to be placed for proper coverage.
Chandler: Particularly challenging is the location and coordination of notification devices to achieve code-minimum sound levels while maintaining intelligibility, where applicable, without appearing to overdesign the system and being "too loud." Coordination with the architectural design to verify wall and ceiling construction, space usage/occupancy, confirm sound reduction, and calculate decibel levels is required to properly design a fire alarm system in an office building.
Yoon: Meeting pathway survivability code requirements for life safety systems in high-rise office buildings is a major design challenge. When UL rescinded UL 2196: Standard for Tests for Fire Resistive Cables, listings for most fire-resistive and circuit-integrity cables back in September 2012, we were caught off guard. The more common solutions-fire-rated chases, concrete encasements, and other similarly inflexible and cumbersome methods-were difficult to implement and unusually expensive. While UL has since started to reinstate listings for certain fire-resistive cables, there are still holes in terms of product offerings and major limitations in how the listed products can be applied.
CSE: Describe unique security and access-control systems you have specified in office buildings.
Chandler: Integration of access-control/video-surveillance systems into a comprehensive security-management system is becoming the norm in office buildings. New innovations, such as integration capabilities with building systems, are starting to enter into schematic design discussions. These integrations help create a "smart building" approach to design. With this integration, the building can turn on specific lights and cool or heat specific spaces by recognizing people via their security credentials.
Abramowicz: Aside from the typical card-access systems, our use of biometric access control in office buildings is becoming more widespread. These systems use face recognition and iris readers to grant access to the building and other spaces within. Occasionally, highly sensitive areas in office buildings are provided with fingerprint readers for more secured access. We expect to see the implementation of digital credentialing systems as the future standard. As this technology matures, it will become a mainstream component of the intelligent building.
CSE: What are the recent changes or updates you are experiencing for mass notification systems (MNS) in such facilities? Are clients requesting more "active shooter" notification systems, and if so, how is your team designing these systems?
Yoon: We typically have only encountered requirements for MNS in higher education facilities. Due to the funding sources for these systems (typically, government grants), an MNS usually ends up being installed after the fact as a dedicated, independent system instead of being integrated into a base building’s fire alarm system with voice notification. This can be frustrating, given that incorporating MNS-specific devices only represent an incremental increase in the overall cost of the fire alarm notification system.
Chandler: Some clients are requesting a true MNS. However, most clients are requesting voice-evacuation fire alarm systems that allow for manual emergency announcements via the fire alarm system. KJWW is specifying fire alarm systems with auxiliary inputs and additional microphones for these requests. For many clients, this provides the functions they are most interested in without the excessive requirements of an MNS.
CSE: What are some of the commissioning challenges for proper alarm signaling for office buildings?
Yoon: Consistent testing and documentation for voice intelligibility.
Chandler: One of the primary challenges comes from the interface of the fire alarm system and the BAS. There are numerous fire alarm initiation devices that will activate a response in the BAS, and ensuring they all work properly is a time-consuming task. It becomes considerably more complicated in a retro-commissioning project when the physical connections between the systems are not well-documented. In this case, the testing of each initiation device to achieve the desired outcome may need to be completed without fully understanding how the systems are interconnected.
Abramowicz: One of the biggest challenges in today’s code-driven world of fire alarm and emergency communication system design is complying with the requirements of voice intelligibility. Since 2010, NFPA 72 has required emergency communication systems to produce intelligible messages for effective occupant notification. As AHJs continue to adopt the latest versions of the code, engineers must determine what needs to be done to achieve intelligibility. The materials that comprise a room or space (carpet versus tile, exposed structure versus drop ceiling, drywall, concrete, etc.), the presence of different furnishings, and the type of occupancy are just a few major factors that need to be considered when designing for intelligibility. Various software is available today to help engineers meet these design requirements, but that software comes at a premium. Long story short, we no longer live in a world where it is acceptable to just place a speaker strobe on the ceiling in a 20-ft x 40-ft conference room, tap it at 1 W, set the candela rating at 75, and call it a day.
CSE: Describe a high-rise office building you recently worked on. What type of elevator, areas of refuge, or other unique life safety methods did you employ?
Abramowicz: The refuge floors for a tall office building that ESD designed use 2-hour compartmentation for the protection of the occupants on the refuge floor. In addition, the refuge floors are provided with mechanical pressurization to minimize the potential for smoke migration into the refuge area. Additional compartmentation features incorporated into the design include ducts that pass through the refuge floor, which serve other areas to be separated by 2-hour construction, and mechanical rooms on the refuge floor serving only the refuge floor. The pressurization system for the refuge floor is activated by any fire protection or alarm system within the building zones adjacent to the refuge floor. Pressurization fans are dedicated and located in 2-hour fire-rated enclosures. Stair and shaft compartmentalization and pressurization are also important. The overall height of stairs and shafts is limited by stack-effect pressurization gradients. We actively work with the architect to determine the "break points" that will make pressurization work with the code requirements.