Renovation of cleanrooms presents challenges
Design and construction teams facilitate renovations of existing space to ensure projects are completed on time, within budget, and to the satisfaction of owners.
By Kenneth J. Mouchka and Roger Herndon
Every year in the United States thousands of cleanrooms are built and certified for production purposes. Thousands more are either modified in service, renovated, expanded or built in existing buildings. Designing cleanrooms within existing spaces presents a formidable
challenge to architects, engineering consultants, owners, user groups and building officials throughout the industry. While other projects often take place within existing parameters of production or other circumstances, those cleanrooms that are built in existing facilities represent:
Production areas leased or purchased by start-up companies with no direct experience in cleanroom design, construction or facilities maintenance;
Design and construction problems that must be overcome in spaces that may be ill-suited to cleanroom construction, and;
Projects with conditions of design and construction that may seem impossible to meet.
More often than not, a company in need of clean production space is more interested in “hitting a market window” than in understanding and appreciating the challenges associated with cleanroom design. Marketing in the high-tech industry calls for split-second decision making and fast response. Without sufficient experience in this sport, an owner will spend as little time as possible in design team and contractor selection. Be it big firm, little firm, work load, consultant group mix, experience in the building type, number of cleanrooms designed/certified — there are too many things to consider and score. Many design and construction groups have sufficient experience and are well-qualified to perform in this arena. All things being equal, the owner would be well-advised to find a group that fits the corporate personality and whose participants appear to be committed to the project team for the duration of the project. A positive “chemistry” or “energy” between participants is difficult to quantify on a scoresheet, but is as important a measure of the potential for success as any other aspect of the selection process.
What motivates owners to build their production facilities in existing spaces? At thousands of dollars per square foot, any leverage toward improving square foot costs is incentive enough, no matter what the challenges. Smaller companies in need of cleanroom production space often lack the capital necessary to fund new construction, especially before products are recognized and R&D or pilot yields are at levels that warrant expansion.
What are owner/user group concerns with respect to “new” cleanroom space within existing facilities? The answer is budget, quality and time. But in the high-tech industry, where one is operating in existing space until the operation gets off the ground, these characteristics are usually prioritized as time, quality and budget.
There are two common approaches to the project delivery process: in one the designer and builder contract separately, and in the other, the designer and builder work as a team. Frequently, designers and contractors are selected within the same timeframe, forming a team organized along traditional lines, dedicated to a negotiated methodology of delivering the project. In this case, designer and builder contract directly, but separately, with the owner. Design/build teams, on the other hand, normally with the contractor in the lead, are seen as integrated groups whose purpose is to act seamlessly, and quickly, in developing the project. A design/build team offers the owner a single point of contractual contact. In both cases, an awareness of the problems facing each member of the group is key in delivering a successful project on time, on budget and in a way that enables the owner to begin his production operations on schedule in order to meet marketing goals. Teamwork between the owner, designer and builder cannot be overemphasized.
Owners will become overwhelmed with, and sometimes resentful of, the storm of questions generated by the design team in their search for the proper criteria on which to base their designs. Owner/user groups should be prepared for this, and designers need to recognize that the owner cannot answer everything at once. Prioritizing needs and setting realistic time frames for establishing criteria, developing solutions and working around existing conditions will allow all team members to manage a process that can be frustrating at times, but successful in the end.
Project management
At the outset of the design process, it is important for project managers of key team members, particularly architect, mechanical engineer and contractor, to establish strategies for addressing special concerns. Some key points:
What is the owner`s vision for the project? Does he expect a BMW or a Ford? This will help greatly in allowing designers to recommend materials and solutions that are appropriate to both the vision and the budget. Owner expectations extend to “softer” considerations as well. If he leads a tour through the facility, what message does he want to leave with the customers? Will they be impressed with special architectural features and finishes or do they want to know that this a hard-working, no special frills operation? Are customers interested in the details of the cleanroom manufacturing process? Is security a special concern? Answers to these questions will lead the design team in the right direction when it comes to selecting and recommending finishes or special details and planning circulation systems throughout the facility. Whatever “word pictures” an owner can apply to aspects of this operation will be extremely helpful to the architect, whose often unenvious responsibility is to interpret and coalesce programmatic requirements and corporate vision.
It is important to understand the owner`s decision-making process. Frequently, the design process will uncover philosophical differences within the owner group, particularly between manufacturing and production staff, facilities maintenance, engineering groups and company management. The owner should be prepared to organize and manage the decision-making process to avoid sending contradictory signals to the design and contracting team.
What is the capability of the owner`s in-house staff? Owner staff members are often expected to facilitate the design process by acting as liaison to the design and construction team while discharging their normal duties as well. Overworked staff will not be able to respond to the needs and questions presented to them by the designers or builders in a timely way, effecting the schedule directly and budget eventually. The owner can eliminate this problem by dedicating the appropriate staff members to the effort or placing the burden elsewhere.
Construction within an operating cleanroom, sometimes a 24-hour operating environment, will present special challenges to the contractor. It must be clear, at the beginning of the process, under what conditions the contractor will be required to work. Working arrangements will require careful planning by the owner and contractor, and compromises by both parties will be necessary to allow the work to proceed while quasi-normal owner operations continue. Establishment and maintenance of the appropriate cleanroom protocols by the contractor will require close coordination. The owner should expect to be directly involved in the process to assure the working/production environment will continue to perform as expected. Routine training and monitoring of construction personnel is essential. Establishing expectations for the execution of the work will translate into more realistic budgets and schedules.
Planning and design
Any design problem begins with an understanding of an architectural program. In the case of cleanroom design within existing spaces or in the case of expansion this amounts to understanding the manufacturing or cleanroom process and understanding the limitations of the existing facility.
For architects, understanding the manufacturing process will center on issues of material flow and circulation by staff:
How do raw materials enter the facility? What are material handling and receiving requirements? What kind of equipment is necessary for handling, how much room does equipment need to operate properly, how is equipment serviced and how big do openings need to be in order to navigate easily through the facility?
What steps are taken in manufacturing the product? This is often proprietary information, commonly withheld by the owner. However, the architectural concern here is one of circulation of the product interfering with means of egress from the facility in case of a fire or other calamity. These two circulation issues often clash since the owner`s manufacturing engineers are interested in an efficient, uninterrupted, straight-line flow, while building officials and fire marshals are concerned strictly with life/safety issues. In every case, life/safety will prevail, however, and the product path will have to find another route.
What are the architectural needs of the manufacturing equipment? Without bumping into proprietary information again, the architect will need to know how the equipment gets from the loading dock to its place in the cleanroom. Are openings large enough? Should they be demountable; how often is equipment moved? How heavy is the equipment; should special thought be given to floor slabs, joints or foundations? What kinds of utility services are necessary; how should we clear paths to connection points? Should utilities be delivered from above, below or behind the equipment? What path options are eliminated because of existing facility constraints?
What types of hazardous production materials (HPM) are used in the manufacturing process? This information is frequently difficult to collect from owner/user groups, either because of its proprietary nature or less-than-complete record keeping. However, it will have a direct impact on code classifications of certain areas and lead to requirements for fire separations between building areas and special alarm and fire protection systems. Recent code changes have modified the classification of HPM chemicals and the allowable quantity of these materials that may be stored. This area of design is becoming more frequently addressed by specialty consultants.
How is the product inspected? Inspection is commonly the last step of the manufacturing process and sometimes involves special equipment to physically test the product. This sometimes involves heat or vibration-producing devices whose effects on the surrounding areas of the building need to be mitigated.
How is the product packaged and shipped? Does this packaging require special provisions for handling paper products, plastics, shrink-wrap machines? Each packaging type could have effects on flooring materials, lighting, acoustics and mechanical systems. Product shipping may require different facilities than receiving although these two functions are closely linked.
An examination of an existing building that will receive cleanroom facilities will require the architect to look carefully at column grid spacing, clear height from the floor to the underside of the structure, roof load capacity, floor load capacity and seismic resistance capability.
Column spacing will influence the location and dimensions of clean bays and service chases and sometimes interferes with process flow and equipment locations as well as the ability of the cleanroom layout to be expanded or modified in the future. The cleanroom planner should expect to spend a good portion of this time early in the process exploring these options.
The available clear height of the structure will influence the vertical arrangement of cleanroom ceiling height, filter depth, ductwork, fire protection piping, location of air handlers and available space for servicing elements above the ceiling. In a situation where height is limited, air handlers can be moved to the roof, if loads can be accommodated, and return air arrangements can be through the sidewalls of the cleanroom rather than below the floor.
Roof load capacity can limit the ability to locate major mechanical equipment on the roof without additional structural support. Methods of support for racked utility piping also will be influenced by roof capacity and may require that these loads be floor supported. In any case, an allowance for additional future loads should be considered since cleanroom technology requires constant tinkering, resulting in new loads and unforeseen requirements.
Lateral resistance to earthquake loads has become an increasing concern, especially in the western United States, due to recent code changes and the owners` interest in the ability of their facilities to reasonably withstand a seismic event of a certain magnitude. Existing buildings, designed and built under the requirements of earlier codes with less stringent requirements, may be required to be seismically upgraded as part of new remodeling work. This can add significantly to the cost of a project depending on the type of structure, its height, its configuration, soil conditions and the seismic classification of the area as determined by the building code in effect. Frequently, a seismic upgrade can take the form of additional bracing or shear walls and modification of structural connections. The ease with which a contractor can access the structural frame, without doing serious harm to existing wall, ceiling or floor finishes or the exterior shell of the building, will have a direct effect on costs and schedules.
Walls, ceilings and floors
The selection of cleanroom walls, ceiling and floor systems can vary widely depending on the cleanroom classification, frequency with which equipment is added or changed, cost, durability and maintainability (see “Cleanroom Ceilings, Floors and Walls,” CleanRooms, Dec. 1995, p. 12). Depending on the systems selected, several considerations should be taken into account.
Modularity. These components ordinarily are manufactured and assembled in modular fashion, in 2- or 4-ft increments. Planners should pay particular attention to aligning the modular characteristics of independent components in order to simplify construction or accommodate future changes. The challenge will be to coordinate events happening below the floor (access floor pedestal layout, recessed slab offsets) with events occurring above the ceiling (ceiling suspension system and supporting structural system, ductwork, fire protection head layout).
Recessed vs. raised access flooring. Where return air paths require perforated access flooring the designer and owner are faced with decisions related to the position of the access floor with respect to the existing finish floor of the building. Recessed solutions offer level access to cleanroom spaces and are clearly an operational preference, but in existing buildings may require slab removal, excavation and new forming, pouring and finishing of concrete surfaces. In cases where structural columns penetrate the access floor, foundations may need to be lowered. Raised solutions are by far the least expensive, however, in situations where vertical space is at a premium, they will require more height as well as ramps, with accompanying stairs, handrails and closure aprons. Ramping also requires more floor space in order to meet accessibility requirements.
Wall closures at equipment. Some forethought is necessary with respect to wall system penetration by equipment and the closure of these openings against the equipment. Some wall system manufacturers offer accessories to accommodate these openings. Irregular openings will also require special framing to support the wall system and may have to be removable.
Vision. Windows or relites in cleanroom wall systems are often considered for a variety of reasons. The visual connection between space mitigates worker fatigue, can improve communication among staff members and often occurs along a tour path allowing owners to spotlight special features for clients or investors. If the opportunity presents itself, properly positioned relites can also offer a cleanroom worker a view to the outdoors. Opportunities for positioning relites are sometimes scarce since equipment, panels or utility services frequently occupy these wall spaces. In these cases, positioning relites higher than usual (between 6 and 10 feet) may serve the same purpose and not interfere with these elements. Return air chases also are used for vision purposes, however these require two glazed openings rather than one, and special treatment of the open plenum may be necessary to conceal unsightly items.
Mechanical considerations
Maintaining laminar air flow within cleanroom spaces is central to successful cleanroom design. Although the mechanical engineer will address HVAC equipment design, air changes, velocity, temperature and humidity controls, the architect assumes responsibility for the design of the physical environment that will influence airflow. These factors can take many forms.
Flush is beautiful. Any offset of obstruction extending from a vertical surface will have an effect on laminar airflow. Relite heads and sills, hardware, equipment, piping and similar elements will contribute to the disturbance of laminar flow if not properly treated.
Location of return air plenums will determine airflow characteristics through a cleanroom space. Although the mechanical engineer will provide the architect with the square footage requirements for plenum openings, the position of these openings should be reviewed thoroughly with user groups to assure that fixed or moveable items in the cleanroom will not obstruct the return air path.
The width of a cleanroom will be a factor in cases where low sidewall air returns are employed. Laminar airflow from the ceiling will flow toward these returns, “bending” in such a way as to cause slack air “tents” in the center of the room. These tents are not always avoidable, but knowing they will occur will allow the designer to minimize them or keep sensitive material to one side.
In cases where a fully filtered ceiling is not required, the distribution of light fixtures and filters, and the relationship between filters and return air grilles, will influence airflow characteristics as well. Where filters are “ganged” in certain areas of a cleanroom, slack eddies will form elsewhere in the cleanroom, trapping what may be particulate-laden air.
Cleanroom design and construction clearly has become a specialty practice for architects, engineers and contractors alike. Applying this special knowledge to cleanrooms in existing facilities, remodeling or expansion projects, presents unique challenges. However, understanding the principles of the problem, listening very hard to the requirements of the owner/user group, and applying time-honored practices of architecture and engineering will lead to successful projects. Couple this with a strong team approach involving partners in the contracting community and knowledgeable owners, and you have every chance of achieving what, at the outset, may have seemed impossible. n
Kenneth J. Mouchka, AIA, and Roger Herndon, AIA, are principals in the architectural firm of Boucher Mouchka Larson Architects in Portland, OR.
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Figure 1: Cross-section of a renovated cleanroom.
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Plenum space above Class 10 cleanroom in an existing renovated structure.
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Service bay with plenum access for a Class 10 cleanroom renovation.