A cleanroom can look meticulously finished and still fail to perform to requirements.

The walls may be sealed. The surfaces may be easy to clean. The equipment may be installed exactly where it belongs. But if humidity rises during the summer, pressure changes every time a door opens, or the HVAC system cannot maintain the required environmental conditions when production is running, correcting those problems after construction is often far more complicated than addressing them during design and preconstruction.

A cleanroom is much more than a tightly constructed room with specialized walls, ceilings, and finishes. Its ability to maintain the required environmental atmosphere depends heavily on the mechanical, electrical, and plumbing (MEP) systems designed into the facility. HVAC and dehumidification are especially important because together they help control airflow, filtration, temperature, humidity, and room pressure, all of which are critical to maintaining consistent cleanroom conditions.

For that reason, MEP planning needs to begin alongside the cleanroom design—not after the physical space has already been laid out.

Why Is HVAC So Important in Cleanroom Construction?

In a typical office or commercial building, the primary purpose of HVAC is occupant comfort.

In a cleanroom, a properly designed HVAC system is essential to maintaining the environmental conditions required for manufacturing, testing, laboratory work, healthcare applications, and other contamination-sensitive operations.

Think:

• Airborne pathogens
• HEPA Air filtration
• Temperature
• Relative humidity
• Positive pressure
• Airflow direction
• Air volume
• Process-generated heat
• Fresh-air requirements
• EPA exhaust regulations

For example, adding exhaust may affect room pressure. Increasing outside air may increase the moisture load. Production equipment may generate enough heat to change the cooling requirement. The location of supply and return air can affect how contaminants move through the room.

This is why cleanroom HVAC cannot be treated as an isolated mechanical specification.

It needs to be coordinated with the room layout, production equipment, exhaust requirements, adjoining spaces, building envelope and operational requirements.

How Does Humidity Impact Cleanroom Operations?

In a cleanroom, excessive or insufficient humidity affects processes, products, materials, equipment, and cleanliness requirements.

Depending on the application, poor humidity control can contribute to issues such as:

• Condensation
• Corrosion
• Static electricity
• Microbial growth
• Changes in sensitive materials
• Process inconsistency
• Equipment problems
• Product-quality concerns

It’s important to note that optimal humidity ranges vary from one operation to another. There is no single relative-humidity setting that is appropriate for every cleanroom.

Cleanroom environmental conditions need to be established early enough for the HVAC and mechanical systems to be designed around them.

Why Can Dehumidification Become a Construction Issue?

A conventional HVAC system naturally removes some moisture while cooling the air, but such conventional cooling often does not provide the strict humidity control many cleanrooms need.

Some applications require tighter moisture control or encounter moisture loads that justify dedicated dehumidification.

This becomes particularly relevant in climates such as Wisconsin and the upper Midwest, where outside-air conditions change dramatically throughout the year.

A cleanroom that performs well on a cool spring day still has to perform when hot, humid summer air enters the building.

Moisture can also enter through:

• Required fresh air
• Doors opening
• Personnel, particularly in smaller rooms
• Production processes
• Washdown or sanitation procedures
• Adjacent spaces
• Air leakage through the building envelope

Depending on the project’s requirements, the mechanical design may incorporate refrigeration-based dehumidification, desiccant systems, reheat strategies or other approaches.

The construction team’s role is to make sure those systems can actually be installed, coordinated, accessed and integrated with everything else happening in the facility.

That is where early mechanical, electrical, and plumbing (MEP) coordination becomes especially important.

How Are Pressure Differentials Maintained?

Cleanrooms frequently rely on pressure relationships between adjoining spaces.

In some environments, the cleanroom may operate at a higher pressure than surrounding areas so that when a door opens, air tends to move outward rather than allowing contaminants to enter.

Other specialized environments may use negative pressure when containment is the priority.

Either way, maintaining the intended pressure relationship requires more than installing the correct air-handling equipment.

Supply air, return air and exhaust need to remain balanced. Doors, wall penetrations, ductwork, process exhaust, ceiling systems and the integrity of the room envelope can all influence pressure.

This illustrates an important point about cleanroom construction: the room and its MEP systems cannot be designed and built independently of each other.

What Electrical Requirements Should Be Planned Early?

Cleanroom electrical requirements extend far beyond lighting and convenience outlets.

Depending on the operation, the electrical system may need to support:

• Production or laboratory equipment
• HVAC and dehumidification systems
• Filtration equipment
• Exhaust systems
• Controls
• Temperature and humidity sensors
• Pressure monitoring
• Alarms
• Building automation
• Data connections
• Emergency or backup power
• Clean power
• Hazard classification (Class 1 / Division 1)
• Substance being utilized / stored within the space

Waiting until equipment arrives to determine power requirements can result in rework, additional penetrations, schedule changes or conflicts with mechanical and architectural systems.

Every new penetration through the cleanroom envelope also needs to be considered from the standpoint of sealing and environmental control.

What Plumbing and Process Utilities Need to Be Considered?

Cleanroom plumbing requirements vary considerably by industry and process.

They may include conventional plumbing as well as:

• Process water
• Purified water
• Drainage
• Compressed air
• Specialty gases
• Equipment cooling
• Sanitary systems
• Process piping
• Washdown requirements

The location of equipment can influence where these utilities need to be delivered.

While that sounds obvious, the consequences of getting it wrong can be significant. Moving a power connection may be relatively straightforward. Relocating an underground drain after concrete has been placed is a different matter.

This is one reason equipment layouts and utility requirements should be addressed during preconstruction rather than left for field coordination whenever possible.

The Building Envelope Has to Support the MEP Design

A sophisticated mechanical system cannot completely compensate for a poorly constructed cleanroom envelope.

Walls, ceilings, floors, doors, penetrations and transitions all influence the ability to maintain controlled conditions.

• Air leakage may make pressure control more difficult.
• Poorly coordinated penetrations can create potential contamination pathways.
• Materials and finishes may need to accommodate frequent cleaning or the specific requirements of the operation.

The architectural construction and MEP systems therefore need to work as a single coordinated system as early as practical during design and preconstruction.

What Happens When MEP Coordination Starts Too Late?

Decisions made by one trade in isolation impact the others.

Consider a few examples:

If these issues are discovered after construction is underway, the solution may involve costly redesign, expensive change orders, and schedule delays.

That is precisely what smart preconstruction is intended to minimize.

Start With the Process, Not the Room

One of the most useful questions at the beginning of a cleanroom project is not:

How large should we make the room?

It is:

What does the operation taking place inside the room require?

That discussion needs to address:

1. Required cleanliness level
2. Temperature requirements
3. Humidity requirements
4. Pressure relationships
5. Airflow and filtration needs
6. Process and equipment heat loads
7. Exhaust requirements
8. Electrical loads
9. Plumbing and utility requirements
10. Personnel and material movement
11. Cleaning procedures
12. Monitoring and control requirements
13. Maintenance access
14. Future equipment or process changes

Once those requirements are understood, the design and construction team has a much stronger foundation for making decisions.

Good Cleanroom Construction Starts Before Construction

The most visible parts of a cleanroom are rarely the only parts that determine whether it works.

Much of its performance depends on systems hidden above ceilings, behind walls and within mechanical rooms.

That makes coordination one of the most important aspects of the project.

Bringing the owner, design team, contractor, equipment suppliers and key MEP trades into the process early provides more opportunities to identify airflow, humidity, pressure, utility and constructability issues while they are still relatively easy to solve.

For a cleanroom project, good construction doesn’t begin when the first wall goes up.

It begins by understanding exactly what the room has to do.