Cleanroom Design: Proper Planning and Construction of Ceilings and Their Installations

Fig. 1: Clamping cassette ceilings are non-occupiable, suspended metal ceilings. Lights and air outlets can be integrated into the system almost seamlessly across the surface. (Copyright: Jens Distelberg)

Fig. 2: The Glatt Granulator GPCG was integrated here into a graded support grid ceiling in a cleanroom-compatible manner. (Copyright: Glatt)

Fig. 3: The fully welded cleanroom washing station made of stainless steel, developed by Glatt, is completely free of silicone joints and can be seamlessly connected to all common cleanroom ceiling systems. (Copyright: Jens Distelberg)

Fig. 4: Light fixtures, ventilation outlets, sprinkler heads, and sensors should, as far as possible, always be integrated flush with the ceiling systems. (Copyright: Jens Distelberg)

Clear requirements in current GMP regulations and other applicable standards define how a cleanroom must be constructed. In practical implementation, these meet the needs of the client and must be considered when selecting the system and during on-site execution. An approach to the realization of cleanroom ceilings is explained by Ronny Töpfer, project engineer at Glatt Engineering, Weimar.

What applies to the design of doors, glazing, and walls in the cleanroom naturally also plays a major role in the cleanroom ceiling: All planning questions must be carefully addressed before implementing a renovation or new construction project and clarified in close collaboration with the customer. As part of the concept, questions regarding installations in the ceiling cavity, such as lighting, ceiling fixtures, and air outlets, should already be coordinated early on. It is crucial that all involved trades are closely integrated into the planning process. Glatt Engineering, for example, relies on in-house specialists for HVAC, EMSR, process, black and clean media. This allows all trades to be coordinated directly without friction. When external service providers are involved, they should be integrated into the project structures as closely as possible.

Ceiling systems and their application areas

In cleanroom ceiling systems, there are essentially three types: support grid ceilings, clip-in cassette ceilings, and panel ceilings. They are generally used from ISO class 8 cleanrooms upward. For less stringent cleanroom areas, dry construction and cleanroom-compatible paints are conceivable. As with wall systems, ensuring airtightness through minimal joint gaps is also important here. The execution of cleanroom panel ceilings is similar to that of wall panel systems. Depending on the supplier, there are cantilevered, walkable ceilings with spans up to six meters, which minimizes the number of joints. Thanks to integrated profiles, such large-format elements can also be easily attached to the raw ceiling or steel substructures. Lighting and outlets are conveniently installed before the final assembly. Retrofitting fixtures is only possible to a limited extent and with greater effort compared to other systems. Whether the ceiling should be walkable or not is an important aspect. For panel and support grid ceilings, walkability can be provided if desired, eliminating the need for additional gangways or other structures. However, the load capacity of all systems is limited. It is mainly intended for maintenance purposes and not for supporting pipe brackets or other loads in the ceiling cavity.

System-dependent design options

Support grid ceilings consist of a manufacturer-specific, flexible grid system with extruded profiles. The width of the grid bars varies depending on the manufacturer, with installations such as pressure sensors fitting well into widths starting from 80 mm. Ceiling panels are available in common sizes, such as 625 mm x 625 mm, allowing cleanroom lighting and air outlets to be installed without additional joints. The market also offers a range of other sizes or custom dimensions. Clip-in cassette ceilings are non-walkable, suspended metal ceilings. As with other systems, lighting and air outlets can be integrated almost seamlessly into the system.

The previously mentioned airtightness of the ceiling plays a crucial role. Similar to cleanroom walls, joints in the ceiling reflectance can be sealed with cleanroom-compatible silicone. Silicone sealing is not used for clip-in cassette ceilings, as these should only be installed in lower cleanroom classes. In addition to silicone sealing, dry seals can also be employed. It should be coordinated with the client beforehand how often the cleanroom ceiling needs to be opened, for example. Silicone seals must be renewed each time, whereas dry seals are installed above the joints and do not need to be replaced upon opening. A disadvantage of dry seals is a higher leakage rate and a small, design-induced gap.

Close coordination during the concept phase

During the planning of the cleanroom, close coordination with the customer and architect is essential, especially since, unlike new construction, renovations are naturally constrained by architectural conditions. Spatial requirements and clear room heights are usually determined by the customer and their project specifications. The cleanroom planner has limited influence here, as spatial conditions and equipment sizes are dictated by the process. Influencing factors set by architecture can include container dimensions or the installation of hub columns. Sometimes, ceiling domes are used to efficiently reduce the actual cleanroom volume. The larger the cleanroom volume, the higher the demands on air management, which results in increased ongoing costs. An important aspect of pre-planning a new build is the structural height of each floor. Often, it is only during the construction phase and installation of above-floor components such as pipes, ventilation ducts, and sprinkler lines that it becomes apparent that the plenum space is very tight and that all installations can only be accommodated with significant engineering effort. Here, an accurate preliminary estimate of installation density and sizes, such as ventilation ducts or lighting, must be made. Convenient maintenance access at all necessary points is a must and should be considered and planned accordingly, especially for safety-critical components like sprinkler lines. Their integration is crucial and often mandated by insurers. Fire protection systems, in particular, cannot be arbitrarily routed and are subject to strict regulations. If the plenum and cleanroom are to be sprinklered, space and installation requirements increase significantly across all areas.

Proper integration: fixtures in the cleanroom ceiling

Cleanroom ceilings can accommodate various fixtures, all of which must be properly integrated to meet the respective cleanroom class. The most common include:

• Lights,
  
• Air inlets and outlets,
  
• Filter fan units,
  
• Sensors such as temperature sensors, pressure or humidity sensors,
  
• Emergency exit signs,
  
• Smoke detectors,
  
• Sprinkler heads,
  
• WLAN antennas, and more.

The requirements for a smooth and surface-bonded design of the cleanroom also play an important role in these fixtures. For lights and ventilation outlets, this is less of an issue, as common cleanroom manufacturers already offer these components seamlessly integrated into their ceiling systems. It is also possible to adapt ceiling systems so that fixtures and outlets from other providers can be retrofitted to meet cleanroom standards. Sensors should ideally be integrated into the grid profiles to allow maximum flexibility for ceiling elements. Many suppliers support this. Alternatively, fixtures can be integrated into the ceiling panels, which naturally limits flexibility in the ceiling reflectance. Not all sensors can be surface-mounted, but the market offers a variety of cleanroom-compatible sensors and other suitable components. Particularly for sprinkler heads, there are good specialized solutions, such as automatically retractable nozzles in case of fire.

Cleanroom lighting can be accessible from below or from above for maintenance. The version accessible from below allows defective modules to be easily replaced without compromising the cleanroom status—a significant advantage. This option is also suitable when access from above is hindered or impossible due to space constraints in the plenum. The fundamental principle for lighting planning in every cleanroom project remains: the client should be involved from the start to jointly determine the best solution for the construction project, and all trades must coordinate closely. Ideally, all planning services are provided in a coordinated manner from a single source.