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.