Getting it right in mixed-use buildings: Electrical, power, and lighting
Mixed-use buildings—often a combination of retail and residential—are unique structures with varying needs. Electrical systems, power supplies, and lighting systems are a big part of the puzzle.
Michael Albanese, PE, LEED GA, Senior Associate, Kohrs Lonnemann Heil Engineers, Fort Thomas, Ky.
David Callan, PE, CEM, HBDP, LEED AP, QCxP, Vice President, McGuire Engineers, Chicago
Donna Miller, PE, PEng, LEED AP, Vice President, Engineering, WD Partners, Dublin, Ohio
Gary Poole, PE, Principal, Bury Inc., Houston
Andrew H. Smith, PE, CEM, LEED AP, Principal, Jordan & Skala Engineers, Dallas
CSE: Describe some recent electrical/power system challenges you encountered when working on a mixed-use building.
Smith: Coordinating preliminary electrical loads with utility companies to size power to the site can be difficult at times. There is a constant battle of how to service the site, how many transformers are required, and where to locate transformers on a tight mixed-use site.
Poole: It is always a challenge to reconcile code-mandated Watt-power densities with the power for the equipment and lighting that is being installed and the sizing of the system components. We work closely with electrical equipment vendors so that the systems are not sized larger than needed, but still have the flexibility to address future loading.
Miller: The biggest challenges we encounter with electrical power systems are with our renovation projects, particularly partial renovations. We recently contended with a partial-renovation project where neither the original drawings nor as-built documents were available for our use in developing the new design. Our electrical engineers spent a considerable amount of time in the field documenting the electrical distribution system so that we would have a basis for our design. Our second biggest challenge occurs when we encounter the need to engineer multiple utility meters/service entrances for a mixed-occupancy facility. Often when the facility is multiple stories with multiple occupancies, such as a lifestyle center with retail, parking, and living spaces, the coordination of the routing of service conductors and determining the location of metering equipment can become challenging. In this instance, we work closely with the architects to determine the most cost-effective and code-compliant solution.
Callan: Power quality and medium-voltage distribution are always difficult in super-tall structures and large mixed-use buildings. While one might argue that the distribution of subatomic particles needn't occupy so much real estate, we must remember that the safety of inhabitants is important. Basically, the costs and practicality of distributing lower-voltage power throughout a large facility leads to the distribution of medium-voltage power. This often leads to the encasement of potentially lethal power lines in large, space-stealing, concrete pathways. And it necessitates the regular step-down transformation and replication of distribution equipment throughout a building. Lastly, once the huge electrical systems are connected to myriad systems, power quality and harmonics can rear their ugly heads.
CSE: What types of renewable energy systems have you recently specified in a mixed-use building?
Smith: Jordan & Skala has designed photovoltaic (PV) systems on projects that support a small percentage of power. For example, there was a project in San Diego where the roofs were covered with solar panels to power the open breezeway lighting; however, the use of solar and wind on mixed-use is difficult because there are different building types mixed together with different tenant needs. Geothermal is too expensive and would require too large of a well field.
Albanese: A unique project recently completed in Oxford, Ohio, involved a client seeking optimum energy efficiency for an existing multi-use building that included both office and residential occupancies. The proximity of the building to a large pond assisted our engineers in providing a geothermal pond loop system with enough capacity to address the current and future expansion needs of the owner. Ultimately, this system was completed by combining a water-cooled variable refrigerant system with inverter compressors to the geothermal pond loop. This combination improved zoning and energy efficiency for the system.
Poole: While we have designed PV, solar hot water, and ground-source heat pumps for projects, none of them has been for mixed-use projects.
CSE: What unique lighting or lighting control mixed-use projects have you completed?
Poole: One of our long-standing mixed-use clients uses color-changing LED lighting to create a visual "marker" for their facilities. The capabiliities of the newer LED systems are tremendously greater than they were just 5 yr ago.
Albanese: KLH's lighting designers have served on project teams for two major developments, The Banks Phase 1A and U Square @ the Loop (in addition to several streetscape projects, commercial buildings, parking lots, and retail projects). The exterior lighting and controls weren't especially sophisticated for either project, but they attractively accented the architecture. All lighting-certified professionals, they worked with the architect to locate lights and detail mounting so that the residents would not be impacted negatively by the lighting, but it would serve the purpose of highlighting the development and providing a safe environment.