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Tenant and system criteria are keys to making phased renovations work
Another reason for renovating those facilities is that those buildings, whether for the private sector or the government, were designed when energy conservation was not a priority.
The economics and logistics of maintaining and improving federal buildings are the same as in the private sector. To fund capital improvement programs, the federal government relies on rent from tenant agencies. This income stream must be maintained; therefore it is imperative to minimize construction duration. On some renovation projects, tenant agencies must maintain operations and cannot endure any significant down time.
The U.S. General Services Administration has found that one way to maximize rental income while minimizing disruption to government operations is phased renovation. Phased renovation allows a building to remain occupied. The revenue stream, in most instances, offsets the additional time and expense of the phased approach, and is of greater value to the owner than a shorter construction period.
Planning starts with an existing-conditions evaluation. Most buildings built in the ’60s have common challenges, including replacing HVAC and electrical systems; removing asbestos and other hazardous materials; retrofitting modern telecommunications and data communications infrastructure; complying with modern building codes and ADA standards; upgrading fire-protection systems; increasing the building envelope’s thermal efficiency; and improving the work environment.
Sometimes, the owner elects to correct deficiencies as stand-alone projects or as retrofits when a tenant moves out. However, the most cost-effective method is often a full-building, phased renovation.
In a phased renovation, building limitations and tenant-related criteria are primary ingredients in determining how phasing occurs. It is crucial to obtain tenant buy-in at the outset, involve them at all phases, and keep them fully advised of schedules and changes throughout.
Some building limitations become significant when building operations are being maintained, though they are not relevant in a normal unoccupied renovation project — for instance, asbestos abatement containment. Further, all life-safety systems and means of egress need to be maintained in occupied areas. But by far the most significant factor is maintaining HVAC service in occupied areas. How areas are grouped for renovation is determined by how it is possible to isolate those areas with HVAC service.
The impact of the HVAC system in determining phasing can be seen in two projects: the Federal Courthouse and Office Building, Harrisburg, Pa., and the Moorhead Federal Building, Pittsburgh. The Harrisburg courthouse is an 11-story, 225,000-gross-square-foot (gsf) federal office building constructed in 1968. The phased repair and alteration project involved coordination and phasing of 22 different tenant agencies.
The Moorhead Building project is a phased repair and alteration of a 25-story, 783,000-gsf federal office building constructed in 1962. The project is currently in design. Coordination and phasing was required for 55 different tenant agencies.
The Moorhead Federal Building has large air handling units (AHUs) on mechanical floors that service multiple contiguous floors. This design dictated that contiguous floors served by those AHUs needed to be renovated during the same phase.
Other buildings have smaller AHUs on each floor, allowing isolation of multiple noncontiguous floors, as was the case for the Harrisburg building. The ability to isolate HVAC service by individual floors allowed greater freedom in selecting floors to renovate during the same phase.
The typical sequence for phased renovation is simple: vacate tenants from a portion of the building, renovate that space, move tenants from unrenovated space to the newly renovated space, then renovate the newly vacated space, and continue the process until the whole building is renovated. Determining which portions to renovate during which phase, however, is not a simple process and is frequently dictated by tenant criteria.
Renovating whole floors one at a time allows for the shortest construction period and minimal tenant disruption. The ideal goal is to move each tenant from existing space to their final destination in one move. More than likely, however, some tenants will have to move to swing space prior to moving to their final destination. Minimizing the number of moves for each tenant depends on how many floors can be vacated during each phase and the final blocking and stacking of the building.
Blocking and stacking refers to the assignment of floor area locations for tenants. First, existing blocking and stacking must be documented. Next, tenant program requirements, including documentation and analysis of the tenant’s space and functional requirements, must be developed. After extensive interviews, a final housing plan can be developed. This consists of detailed space requirements, including tabular square foot and adjacency information. With that, final blocking and stacking plans can be drawn up.
Consolidating tenants into adjacent space and floors is a major goal for most federal building renovation projects. In the Moorhead building, the proposed stacking plan consolidates the large tenant agencies on adjacent floors. In addition, a buffer floor occupied by smaller tenants was provided between the large tenant floor groupings to allow for potential future growth onto adjacent floors.
Developing the best scenario for moving tenants requires studying many blocking and stacking scenarios until scenarios are found that minimize swing space. Combining single moves with building limitations is the most difficult aspect of determining a final phasing plan.
An economic analysis must determine how much of the building and which floors can be renovated simultaneously. At a minimum, compare the costs of renovating the entire building in one phase; half of the building at a time in two phases; a third of the building at a time in three phases; and one quarter of the building at a time in four phases.
A goal of the phasing plan is to minimize costly swing space. For the Moorhead building, three scenarios were developed and the best selected. Then three additional scenarios were developed; one of those was refined into the final blocking and stacking scenario. The plan included four phases, would take 48 months to complete and required swing space costing $3.7 million.
To further minimize swing space and cut costs, the size of one phase was reduced. With some minor and innovative work, the two AHUs that serve the upper floors were isolated to split the existing top five-floor service into two phases. The proposed plan became a five-phase scenario that ended up with a longer construction duration — 57 months — but a much-reduced swing space build-out, costing only $2.3 million. As a result, the cost of the additional nine months of construction was less than the shorter-phased scenario.
The final phasing plan documents the critical path of who moves to vacate which space, and when. In essence, the restacking of the building becomes the phasing plan.
The Harrisburg building capitalized on the ability to isolate half of each floor. Without a mechanical zoning constraint of grouping multiple contiguous floors, the phasing plan aimed to move tenants to their final destination in one move. In some instances, entire floors were completed in a single phase. In other cases, only portions of floors were renovated.
On phased renovation projects, a partnering approach between facility executives, tenants, architects, engineers and contractors is crucial. By using phased renovation methodology, building owners and facility executives can modernize a ’60s-era building while maintaining occupancy, operations and revenue stream. Capital expenditures can be kept to a minimum with proper planning and optimization of existing building systems configuration. The detailed phasing plan becomes the planning tool for the subsequent successful design solutions, and the multiple construction and occupancy phases of the project.
Charles Enos is a registered architect and principal with Einhorn Yaffee Prescott, Architecture & Engineering, where he is director of the Federal Government Studio for the Washington, D.C. office.
Studies: No Design Flaws in Pentagon, World Trade Center
Two recent studies related to the terrorist attacks on the World Trade Center and Pentagon conclude that the design of the buildings didn’t exacerbate damage.
The Pentagon, in fact, fared well because of its structural integrity, the study concludes. And the World Trade Center, a separate study found, didn’t sustain any more damage than any other building would have in similar circumstances.
The Pentagon’s structural system — spirally reinforced concrete columns supporting a slab, beam and girder system — redistributed the five-story building’s weight to columns not damaged when the airliner struck.
The report, released by the American Society of Civil Engineers, found that redistribution of weight among those closely spaced columns limited the collapse of floors above the point where the airliner struck.
The report recommended features of the Pentagon’s structural frame be considered for structures required to resist progressive collapse:
- Continuity, such as the extension of floor reinforcements through structural supports.
- Redundancy, such as the two-directional framing of floors.
- Energy-absorbing features, such as reinforced columns.
Avoiding progressive collapse has become a top concern since the World Trade Center’s Twin Towers underwent a progressive collapse.
What’s under dispute with the Twin Towers is the exact cause of the collapse. A study by Weidlinger Associates contradicts an assessment by federal investigators who concluded that unconventionally lightweight floor supports in the towers failed.
Matthys Levy, Weidlinger’s chairman, says his firm concluded that the collapse occurred because of intense heat, not structural or design flaws. The impact of the airliners and of flying debris weakened fire-protective coatings, making collapse inevitable given the extreme temperatures.
Larry Silverstein, who holds the lease on the Trade Center, commissioned Weidlinger’s study. At issue is a $4 billion lawsuit involving insurance companies scheduled to go to court in summer. Although Levy discussed the study’s findings, he would not release the report, citing the pending legal battle.
— Mike Lobash, executive editor