Considered the founder of biotechnology, Genentech has been discovering, manufacturing, and commercializing biotherapeutics to address unmet medical needs of patients for more than three decades. Handling such significant responsibilities requires the expertise of world-class researchers working with the most modern scientific equipment in state-of-the-art facilities.

The effectiveness of the chemistry lab’s design in meeting operational and functional requirements was assessed with overwhelming success during mockup testing. Being able to meet these requirements is extremely important because users are adamant about fume hood specifications.

“They did not want to compromise the operability of their fume hoods based on a mechanical solution to meet the air requirements for the room,” says Joe Miller, a senior architect at Genentech. “We did not impact the fume hood sash opening and that is always a challenge. The users always want the largest sash opening you can give them.”

The plenum system provides a uniform distribution of supply air within the lab, which helps eliminate the perception of the wind chill effect created by drafts and turbulence. This particular design feature also reduces the potential for supply air velocity and hood face exhaust disruption, while maintaining zone temperature control, and reducing supply air noise as the air is pushed through the diffusers.

“It reduces the potential of the supply air competing with the fume hood exhaust,” notes Miller. “The fume hood is there to protect the occupant who is working with hazardous chemicals by drawing air from the room over the work surface, thus pulling fumes and odors up the back of the fume hood and into the building’s exhaust system.”

Project Execution

Implementing the plenum system facilitates a reduction in the amount of supply air branch ductwork, as well as the number of air terminal boxes and control points. Supply ductwork is still necessary within the lab, but it requires less distribution. This eliminates conflicts between the exhaust ductwork and the supply ductwork, along with other utilities that have to be located above the ceiling. Although less ductwork is required, the cost of materials for the plenum system ceiling is greater than it would be for a standard suspended ceiling.

Based on the results of the mockup test, Genentech realized a straightforward air balancing and hood certification. Labor savings were achieved with lower detailing costs and a reduced number of coordination meetings. Ensuring the entire project team was involved from the conceptual design phase resulted in the need for fewer coordination meetings and less in-field conflicts. Key stakeholders involved in all aspects of the project, including the mockup testing, were the owner, the client, health and safety officials, design engineers, project manager, architect, contractor, mechanical engineers, subcontractors, and fume hood manufacturer.

“This project was interesting because it was a design-build and we really had to have the buy-in of the entire project team to be committed to trying something a little different,” says Miller. “The design challenges required us to think outside the box, leveraging everyone’s experience and knowledge, looking at different potential solutions, and then validating each one to determine if it was worth pursuing.”

Utilizing the mockup capabilities as a way to validate the solution was a primary key to the successful design of the chemistry lab. All fume hoods passed American Society of Heating, Refrigerating and Air Conditioning Engineers Inc. (ASHRAE) 110 testing criteria on the first pass at the mockup session. The mockup verified that the fume hood functioned as it was designed, therefore assuring certification once installed and operational within the laboratory.

Design Challenges

Research-and-development chemistry labs present many design challenges that must be addressed.

The schedule was aggressive and it had to meet a program that was new to Genentech. The users who were creating the program were very specific about their needs. Programmatic requirements specified the quantity of chemical fume hoods, the necessary utilities, chemical and glycol distribution systems, and equipment/data connections. The designers were also confined by building envelope restrictions associated with putting the new lab into an existing facility with limited square footage and zero exterior changes.

The users were very precise in stating their requirements relevant to the fume hoods. For example, they wanted as much work area as possible and did not want this space to be compromised by the air system. The 7,000-sf lab is divided into two zones with the small-scale research-and-development area having 12 bench-top fume hoods that are each 10 feet wide and the intermediate scale-up area with five 12-foot wide, floor-mounted hoods. The large-scale development suites each have a 16-by-8-foot fume hood with a work area of equivalent size. Numerous exhaust snorkels and ventilated enclosures are required with 50,000 cubic feet per minute (CFM) for the HVAC supply and exhaust.

Other requirements pertained to sash openings, which range in size from 35 to 41 inches wide and 32 to 84 inches high, exhaust needs, hood certification, the need for high CFM flow rates, and room pressurization relationships.

As construction progressed, the ceilings were becoming densely packed. Each fume hood has its own glycol drops and multiple gases. Some of the hoods were connected to domestic water, DI water, solvent dispensing systems, extraction systems, data connections, and electrical outlets.

The design team also had to consider building and fire code requirements pertaining to egress, accessibility compliance, and other issues regarding the HVAC system and the coordination of utilities. Genentech’s own maintenance personnel and engineers offered input into the design process to ensure all of the plenum system’s components could easily be accessed for repairs.

Selecting the Best Ceiling/Air Supply Delivery System

The design team studied four potential solutions for delivering air into the new lab in a manner that best meets all of the program requirements. Included in the lineup of possible solutions were the acoustical tile ceiling with low-flow perforated ceiling diffusers, the acoustical tile ceiling with fabric sock diffusers, the cleanroom plenum ceiling system, and the dual-level suspended tile ceiling air supply plenum, which ultimately was selected as the best solution.

The standard ceiling with the low-flow perforated diffusers presents numerous challenges and requires a large quantity of supply diffusers to meet the CFM requirements. In addition, intense coordination of supply diffuser locations is necessary to ensure the diffusers do not interfere with light fixtures, fire sprinklers, smoke detectors, and HVAC supply and exhaust ductwork.

Using the low-flow perforated diffusers also blocks task lighting, creates the wind chill effect with perceived cold spots and drafts, influences fume hood sash openings, and requires an exerted effort to commission the hoods.

The second system that was considered is the acoustical tile ceiling with fabric sock diffusers. The duct socks represent a fabric variation of the perforated metal ceiling, which is constructed of fabric to distribute and diffuse heated and cooled makeup air. The fabric material is non-absorbent and this particular model discharges air uniformly along the entire length of the system. The exposed mounting extends below the acoustical tile ceiling grid. Despite some positive qualities, however, this system creates a concern about flammability in a chemistry-intensive lab and there has been limited laboratory application.

The cleanroom plenum system seemed promising since it offers uniform air flow throughout the laboratory. However, a dense suspension support system is required and the maintenance access is very limited.

“This system would have worked well if we had an interstitial floor, which we do not have in this building,” notes Albert Oliver, a senior associate with Flad Architects.

After comprehensive searching and brainstorming, the team came upon information about the dual-level suspended tile ceiling air supply plenum system. The upper level is a washable heavy tile and the lower level is standard acoustical. The system relies on plenum delivery and ducted exhaust, which is not a feature the design team initially considered.

At the time, there was no off-the-shelf system available for laboratory application and therefore, Genentech had to customize a solution to meet its needs. The design principals investigated the fabrication of a custom plenum with a ceiling manufacturer and measured the risks of designing, fabricating, and installing the innovative system. The solution was to modify the dual airway ceiling system that was originally intended for installation in an office.

The plenum system, which requires design coordination by all disciplines, was the most logical design solution to meet the needs of the new chemistry lab. This system necessitates the coordination of lighting, sprinklers, glycol, data, electricity, return ducts, alarming devices, solvent waste lines, and solvent delivery lines. The two-level air distribution system has a 12-inch deep plenum, which distributes supply air at high CFM but at a low velocity with room exhaust via the fume hoods. The ceiling uses standard products with a perforated metal panel on the bottom and composite tile on the top. The top ceiling T-bar framing is designed to support both ceilings. The system is also engineered to meet California Building Code (CBC) seismic criteria.

Three-dimensional modeling enabled engineers to see that all of the utilities would not fit above the plenum. As a result, some of the services are located in below-ground slab work. Engineers developed a structural post system on a 12-foot grid to support the ceiling in the event of seismic activity. The posts attach the upper level to the floor slab and the lower level is suspended off the upper level, allowing the ceiling to move with the building.

The ceiling plan features two-by-four-foot lay-in light fixtures and perforated metal panels for supply air distribution at nine and 11 feet. The supply air plenums have four perforated sides and a solid top and bottom. Solid tile is located at the lower level in front of the fume hoods to prevent airflow from coming back in and interfering with the exhausts located overhead.

“Everything is accessible above both levels of the ceiling by lifting up the lower tile and then the upper tile,” says Oliver. “The upper tiles are weighted to keep them from popping up. The same system is used in the larger rooms with hoods that are 12 feet tall, but the ceiling stops at the front of the hoods.”

Mockup of Plenum System Ceiling

Two mockup sessions were conducted at Thermo Fisher Scientific in October and November of 2006 to allow all disciplines to understand how the installation would be performed. All key stakeholders attended the mockup sessions, which featured a full-scale replica of how the system would be installed at the actual lab.

The first test involved the 16-foot fume hood and included the entire room. The air supply plenum ceiling, supply duct boxes, and light fixtures were installed per design specifications. Lab casework was also installed per the floor plan for the mockup using the 10-foot and 12-foot fume hoods. The tests provided all of the necessary HVAC requirements and the plenum ceiling system was utilized twice to simulate different lab conditions.

Fume hood tests were conducted per the performance standards of the ASHRAE. Smoke was utilized in the supply duct to observe the CFM delivery from the air supply plenum system and to monitor the supply air movement within the room.

“This was a group effort with everyone working at the mockup to make improvements and determine the best installation solution,” says John Kelley, a senior project manager at Genentech. “This is going to be a very clean facility with an even airflow.”

The mockup testing results show that all fume hoods met ASHRAE performance standards. The tests also revealed that velocity and tracer gas stability is attributable to the plenum ceiling and hood design, minimal turbulence enables larger sash openings, fewer duct drops feed the plenum system, and the duct drop location is not critical to the success of the hoods.

The fume hood installation took place between February and April of this year and the ceiling was installed in April. The HVAC and air balancing were also completed this spring and the hoods were certified in late May, all in a single day.

Air Supply Plenum System Ceiling Benefits

The plenum system is receiving high ratings for the positive benefits it is producing. In particular, the system does the following:

• provides a high CFM of supply air at a low velocity;
• improves fume hood operation and functionality;
• eliminates supply duct congestion;
• eliminates the wind chill effect created by drafts, hot spots, and cold spots;
• provides area temperature control; and
• reduces noise.

“Right now, we feel confident the system is going to be a success based on what we witnessed during the mockups,” says Miller. “It took a team effort to develop an effective solution based on the criteria we received from the user group.”

By Tracy Carbasho