Three Resiliency Strategies for Developers and Building Owners
By: Randall Duke, PE, LEED AP BD+C, vice president, Cosentini Associates Inc.
Winter 2015 2016
An isometric view of electric service equipment elevated above the storm surge level. Cosentini Associates Inc.
Multiple solutions that modify the placement of a building’s mechanical, electrical, plumbing and fire protection equipment can help a structure avoid or bounce back from storm damage.
IN RECENT YEARS, several notable storms have demonstrated the dramatic impacts that rising sea levels and storm surges can have on commercial buildings. A building that is resilient to storm damage is not necessarily able to stay fully operational and functional throughout the storm and its aftermath. This description typically refers to a structure that is able to return to normal operations soon after the storm has passed. Designs that minimize the damage stormwater can inflict on a building make that structure more resilient.
Resilient Building Design and Management
The tasks of designing and managing buildings that are resilient to stormwater present several challenges. Traditionally, mechanical, electrical and plumbing/fire protection (MEP/FP) services enter a building via below-grade service rooms. This makes efficient use of less-valuable basement and garage space while also enabling services to tie directly into underground utility connections. It also makes these services more vulnerable to flooding. The following three approaches can make them more resilient:
1) Critical service equipment — including electrical service, telephone and data services, emergency generators and fuel supplies, fire alarm systems and fire pumps — can be protected in place, in traditional below-grade rooms, through the use of flood-proof construction and water-tight doors. A water-tight door is typically located in front of a conventional door and is only closed during a flood event. Flood-proof construction can have a significant impact on the structural requirements of walls that will need to hold back several feet of water pressure, and can be quite costly. (See “Cost Factors” sidebar.)
2) Critical service equipment can be located above the storm surge level. In many buildings, this means that equipment rooms must be elevated several feet above ground level, requiring additional area for stairs to access them. The relatively high ceilings found on the ground floors of most commercial buildings make it possible to elevate the floor slabs in these equipment rooms and still provide the required ceiling height.
3) Building management can put in place provisions to allow for quick replacement of critical equipment after stormwaters have subsided. For example, a spare domestic water booster pump can be purchased and stored in a top-floor mechanical room. While not ideal, this option does allow the equipment room to remain in the basement or garage and does not impose any significant construction costs. This approach, however, can only be used with equipment that can be removed and replaced in a short period of time. Having the replacement equipment on hand enables managers to avoid having to track down equipment that may be temporarily unavailable due to post-storm surges in demand.
Several options exist for mechanical, electrical and plumbing/fire protection (MEP/FP) equipment placement.
Cosentini Associates Inc.
When one considers these three approaches, it becomes apparent that a different approach may be appropriate for each system, with multiple solutions applicable to different systems in a single building. Some services, like telephone service equipment, are relatively simple to relocate from their traditional below-grade locations. Others, such as electrical service, are subject to utility company constraints such as ventilation requirements and access for equipment maintenance or replacement. No one solution can be applied to every system or to every building; each project must be evaluated carefully in order to develop a solution that meets the project’s physical constraints and the developer’s program and financial constraints.
Three projects engineered by Cosentini Associates in Boston’s Seaport District illustrate this point. The first has adopted a “protect in place” approach with flood-proof construction to protect below-grade electrical service equipment. The second project located the electric utility company pad mount switch outdoors, elevated approximately 12 inches to raise it above the storm surge. Transformers are located within the building on the ground floor, and are also set on pedestals that elevate them above the storm surge. The building switchboards are located on the second floor. At the third project, the pad mount switch is situated on a pedestal at grade, while the transformers and switchboards are located on the second floor.
As with any decision that affects a building, the location of utilities to mitigate effects from flooding and other severe weather events requires collaboration among owner, architect, construction manager, cost estimator, utility companies, structural engineer and MEP/FP engineers in order to develop cost-effective, creative solutions that protect critical systems.
While installing electrical service equipment in the basement or garage level, first floor, or second floor makes little difference to the electrical trade cost of installation, it can have a significant impact on the overall project construction cost as well as other factors.
Below-grade rooms constructed to protect equipment from floodwater require reinforced poured-in-place concrete wall construction engineered to withstand the sidewall pressure of water in the adjoining space. Ventilation ducts must enter the space from above the flood level, which can impact the design of the floor above. These factors will generally increase the overall project construction cost by hundreds of thousands of dollars.
At-grade electrical rooms take up prime space otherwise available for retail or other revenue-generating uses, which can impact a project’s bottom line. Utility company access requirements typically dictate that these rooms be at the perimeter of the building, which can also affect how lively the streetscape will be. But the construction cost impacts of at-grade electrical rooms are minimal, ranging from zero to about $5,000, depending on project size and location.
Second-floor electrical equipment rooms may require a double-height space in order to provide the required ceiling heights. Removable panels or louvers for equipment replacement can affect the building’s facade. The structural reinforcement to support the equipment will result in some increase in the construction cost, which typically ranges from roughly $10,000 to $50,000, depending on the project.