6.18 Alterations in Existing Buildings and Historic Structures
The goal of GSA’s alteration projects is to approximate as well as possible the facilities standards described in this book for new projects. Renovation designs must satisfy the immediate occupancy needs but should also anticipate additional future changes. Remodeling should make building systems more flexible.
Alteration projects can occur at three basic scales: refurbishing of an area within a building, such as a floor or a suite; major renovation of an entire structure; and upgrade/ restoration of historic structures.
In the first instance, the aim should be to satisfy the new requirements within the parameters and constraints of the existing systems. The smaller the area in comparison to the overall building, the less changes to existing systems should be attempted.
In the second case, the engineer has the opportunity to design major upgrades into the electrical and communications systems. The electrical and communications services can come close to systems that would be designed for a new building, within the obvious limits of available physical space and structural capacity.
Where a historic structure is to be altered, special documents will be provided by GSA to help guide the design of the alterations. The most important of these is the Building Preservation Plan (BPP) which identifies zones of architectural importance, specific character defining elements that should be preserved, and standards to be employed. See Chapter 1: General Requirements, Applicability of the Facilities Standards, Types of Facilities, Historic Buildings.
The electrical systems in historic buildings often differ greatly from today’s design and construction standards, and frequently these systems need to be upgraded substantially or completely rebuilt or replaced. The end result should be a building whose lighting and other electrical facilities support its modern use while retaining its historic and architectural character. Historic light fixtures, hardware and other period features should be retained and any supplementation shall be inconspicuous to avoid detracting from existing historic building ornamental spaces.
The end user requirements are an important part of the programming information for alteration projects. Close interaction between designers and users is essential during the programming and conceptual design phase to meet the users’ needs without excessive construction costs. The general policies and standards that an administrator would give designers are usually not specific enough.
Alteration design requires ingenuity and imagination. It is inherently unsuited to rigid sets of rules. Each case is unique. The paragraphs that follow in this section should be viewed as guidelines and helpful hints to be used when appropriate and disregarded when not.
See Chapter 3: Architectural and Interior Design, Alterations in Existing Buildings and Historic Structures.
Placing Electrical and Communications Systems in Renovated Buildings
Even more than in new construction, the optimal placement of engineering systems in the building structure is a crucial element in the success of the alteration. Vertical and horizontal distribution of utilities must be integrated into the architectural concept from the outset.
Chapter 3: Architectural and Interior Design, Alterations in Existing Buildings and Historic Structures, Placing Mechanical and Electrical Systems in Renovated Buildings describes some of the strategies available for placement of power, lighting and communications systems.
Vertical Distribution. If new risers are required, they should preferably be located in or adjacent to existing closets.Where there is lack of space, communications risers and electrical risers can perhaps be combined.
Horizontal Distribution. Raised access flooring is highly recommended for large modernization projects. Most of the criteria established for raised flooring earlier in this chapter would apply, except that module sizes may have to be varied to fit existing conditions.
In buildings where raised access flooring is not feasible, horizontal electrical and communications distribution may be located in the ceiling. Fortunately, many older buildings have high floor-to-floor heights, which permit an expansion of the existing ceiling space. Vertical zoning of this space between various engineering systems is critical. The zoning should be established according to the principles described earlier in this chapter or according to existing ceiling zones.
In buildings with decorative or inaccessible ceilings, electrical raceways for power and communications lines can be located along walls, or be incorporated into the design of a molding or a special chase between window sills and floor. Raceways should have some additional space for future changes to the electrical and communications systems.
In buildings with fairly close spacing of columns or masonry walls, it may be possible to locate all receptacles, phone and data outlets in furred wall space. The furring should be treated as an architectural feature in historic buildings. If bay sizes are too large for this solution, systems furniture with built-in electrical service is an alternative. Power poles are also an option as long as they are integrated into the architectural design. Poke-through and flat cable should be avoided.
Building ServiceIf new switchgear is provided, consider sizing it according to the loads provided in the section Electrical Load Analysis, Table 6-1, of this chapter even if less than the entire building is being remodeled at the time.
Secondary Power DistributionNew panel boards should be added as required with ample spare capacity. See section Electrical Load Analysis, Standards for Sizing Equipment and Systems in this chapter. In both large and small remodeling projects, panel boards serving electronic loads should be served from an isolation transformer and sized with consideration given to harmonic currents.
Computer Center PowerNon-linear computer loads should be isolated from normal power. Ensure that the size of the supply transformer for non-linear loads is rated and protected on the basis of input and output current. Provide circuit breakers with true RMS overload protection on the supply and load sides of the transformer and increase the size of the neutral to twice the size of the phase conductor.
LightingGeneral Renovations. For small remodeling projects, existing lighting systems should be matched for uniformity and ease of maintenance. In total building modernizations, the guidelines established in the section Lighting of this chapter should be followed.
In structures with ornamental or inaccessible ceilings, indirect lighting offers many possibilities. Fixtures may be located in wall coves or at the top of low columns or partitions.
Historic Structures. In historic buildings, the quality of the fixtures and the quality of the light are integral to the architectural integrity of the building. The character of many old buildings has been compromised by poor lighting designs. Designers are encouraged to seek imaginative solutions to achieve required light output while preserving the essential visual characteristics of historic lighting, such as variable light levels, highlighting of architectural features, light source color, reflected patterns, and the surface reflectivity of historic materials.
Many historic buildings have beautiful plaster ceilings that do not permit use of lay-in fixtures. Indirect lighting from coves, combined with task lighting, can be a good alternative.Wall sconces are another alternative, particularly in corridors. In public spaces, chandeliers or other decorative fixtures may need to be restored or duplicated.
These fixtures may be retro-fitted with compact fluorescent lamps, reflectors, and other light sources to increase light output and energy efficiency. Use of halide lamps as the sole light source in historic fixtures is discouraged because of differential color shifting that occurs as lamps age.
Reproduction historic lights for significant spaces such as courtrooms may be fitted with multiple light sources and separate switches to allow for multiple light levels. Select lamps providing color rendition as close as possible to that of original lighting. In historically significant spaces requiring increased light levels, apply the following order of preference:
1. Retrofit historic lights with energy efficient ballasts/lamps
2. Add discretely designed supplementary lighting, preferably reflected light, to avoid competing with period lighting.
In historically significant spaces, supplementing of ceiling mounted lights with wall mounted sconces, indirect lights mounted on furniture, or freestanding lamps is preferable to installing additional ceiling mounted fixtures.
The light source is another important concern. Typically, the existing source is incandescent.Where feasible, the
light fixture should be changed to a fluorescent source, with color rendition as close as possible to that of the incandescent light.
Communications DistributionCommunications systems are specified by the client agency, and they will, therefore, furnish raceway systems criteria for alteration projects.