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Hardwall Cleanroom Design Guide: HVAC & ISO Specs
A hardwall cleanroom is usually selected when a project needs stable pressure control, repeatable environmental conditions, durable cleanable surfaces, or permanent integration with process utilities. Good hardwall cleanroom design starts with the process—not with wall-panel selection. Define particle limits, temperature, humidity, pressure cascade, equipment heat load, personnel flow, and utilities before deciding how many HEPA filters or FFUs to install.
How to Define Hardwall Cleanroom Design Requirements
Select ISO Class Based on Process Contamination Risk
ISO 14644-1:2015 remains the current particle-classification standard in 2026. It classifies cleanrooms by airborne particle concentration from ISO Class 1 through ISO Class 9; it does not prescribe a specific air-change rate for each class.
For many industrial projects, ISO 7 or ISO 8 is adequate, while semiconductor, sterile-processing, and sensitive assembly applications may need ISO 5 or ISO 6 zones.
Design Level | Typical Application | Airflow Approach |
ISO 8 | Packaging, general assembly | Non-unidirectional |
ISO 7 | Medical device, biotech support | Higher recirculation |
ISO 6 | Precision electronics | High HEPA coverage |
ISO 5 | Critical processing | Often unidirectional airflow |
Published supplier guidance shows indicative airflow ranges around 60–90 ACH for ISO 7 and 240–480 ACH for ISO 5, but these are engineering starting points—not ISO requirements.
Define Temperature, Humidity and Pressure Differential Requirements
Temperature and humidity often determine HVAC cost more than ISO class itself. A room controlled at 20–22°C and 40–60% RH is far easier to design than a lithium-battery dry room.
Battery electrode processing can require humidity below 1% RH, roughly equivalent to a −40°C dew point, which demands dedicated desiccant dehumidification.
Pharmaceutical projects have different priorities. EU GMP Annex 1 gives 10 Pa as a guidance value for pressure differences between adjacent rooms of different grades and requires filtered air to maintain the intended pressure relationship.
In our experience, environmental requirements added late—especially low humidity, tighter temperature tolerances, or negative-pressure containment—can change both AHU capacity and project budget significantly.
Calculate Room Size from Equipment, Personnel and Material Flow
Do not calculate room size from production-machine footprint alone.
If equipment occupies 300 ft², circulation, service clearances, worktables, material staging, and personnel routes can easily increase practical room area to 450–550 ft².
Plan separate personnel and material flows where contamination risk justifies it. For US projects, also coordinate the layout with IBC means-of-egress provisions; the 2024 IBC generally requires qualifying door openings to provide at least 32 inches (813 mm) clear width.
Hardwall Cleanroom HVAC, Airflow and Construction Specifications
Size HEPA/ULPA Filtration and Airflow for the Required ISO Class
Airflow should be calculated from particle generation, room volume, recovery requirement, process heat, occupancy, leakage, and filter loading.
For example, a 20 × 30 × 10 ft room contains 6,000 ft³. At an initial engineering basis of 60 ACH:
6,000 × 60 ÷ 60 = 6,000 CFM
That calculation is only a starting point. Final hardwall cleanroom specifications should be verified through particle testing and airflow measurements rather than relying on ACH alone.
ISO 29463-1:2024 provides the current classification, performance-testing, and marking framework for high-efficiency filters.
Choose Recirculating FFUs vs Central HVAC Air Supply
A modular hardwall cleanroom can use ceiling FFUs, centrally ducted HEPA terminals, or a hybrid arrangement.
FFUs provide modularity and easy future capacity changes. Central AHU systems offer stronger control over temperature, humidity, outside air, and pressure but require more ductwork and commissioning.
From the projects we’ve completed, hybrid systems often make sense when the cleanroom needs high recirculation for particle control but only a smaller quantity of conditioned outside air.
Select Wall Panels, Ceiling Systems, Doors and Flooring by Industry
Material selection should reflect cleaning chemistry and process risk.
Pharmaceutical facilities commonly favor sealed coated-steel, uPVC-faced, or stainless-steel surfaces. Electronics projects may require static-dissipative panels and ESD flooring. Commercial modular systems are available with acrylic, static-dissipative PVC, polycarbonate, tempered glass, coated steel, and stainless steel.
A modular hardwall cleanroom is also financially different from a softwall enclosure. A current US cost guide places modular ISO 7 hardwall construction around $150–$250/ft², while ISO 5–6 configurations are estimated around $250–$450/ft², excluding specialized utilities and controls.
Integrate Electrical, Process Gas, Exhaust and Utility Penetrations
Freeze utility locations before panel fabrication wherever possible.
- Electrical outlets and equipment loads
- Process gases and compressed air
- Vacuum connections
- Local exhaust
- Sprinklers and fire detection
- Data and monitoring points
- Utility penetrations and sealing details
Every penetration creates a potential leakage and contamination path. Designing them before installation reduces field cutting and rework.
How to Specify and Procure a Hardwall Cleanroom in 2026
Apply ISO 14644-4 Design, Construction and Start-Up Requirements
ISO 14644-4:2022 covers the process from user requirements through design, construction, start-up, and verification. It specifically addresses requirements definition, construction planning, performance parameters, energy-management considerations, and start-up verification.
This makes a written URS or performance specification essential before procurement.
Compare Pharmaceutical, Semiconductor and Battery Cleanroom Specifications
The same ISO class can require very different systems.
Industry | Major Design Driver |
Pharmaceutical | GMP, pressure cascade, cleanability |
Semiconductor | Particle control, ESD, high airflow |
Battery | Extremely low humidity, process exhaust |
Medical device | Particle control, validated workflow |
For pharmaceutical projects, GMP may drive airlocks and pressure monitoring. Semiconductor facilities may emphasize ULPA filtration and high ceiling coverage, while battery plants can spend heavily on dehumidification.
Build an RFQ Checklist for Comparable Supplier Quotations
Your RFQ should state:
- Internal dimensions and ceiling height.
- Required ISO class and occupancy state.
- Temperature/RH limits.
- Pressure differential.
- Airflow concept and HEPA/ULPA requirements.
- Wall, ceiling, door, and flooring materials.
- Electrical and utility scope.
- Controls and monitoring.
- Installation responsibilities.
- Commissioning and certification scope.
Without these hardwall cleanroom specifications, two quotations can differ by 30–50% simply because suppliers assumed different HVAC, controls, or installation boundaries.
Define FAT, Installation, Commissioning and Final Certification Scope
Specify acceptance testing before issuing the purchase order.
ISO 14644-3:2019 provides cleanroom performance test methods covering areas such as airflow and other controlled conditions, while ISO 14644-4 requires verification during start-up.
A practical handover package should include HEPA integrity results, airflow measurements, room pressure tests, particle classification, control-function tests, filter certificates, drawings, and O&M documentation.
FAQ
What ISO classes can a hardwall cleanroom achieve?
ISO 5–8 are common for commercial modular systems; current products are offered in ISO 5, ISO 6, ISO 7, and ISO 8 configurations. More demanding classifications require project-specific airflow, filtration, sealing, and contamination-control engineering.
How many air changes per hour does a hardwall cleanroom need?
There is no universal ISO-mandated ACH value. Published engineering guidance may use approximately 60–90 ACH for ISO 7 and much higher rates for ISO 5, but the actual requirement should be determined from particle loads, airflow pattern, recovery time, and qualification results.
When should you choose a hardwall cleanroom instead of a softwall cleanroom?
Choose hardwall construction when you need reliable pressure control, tightly controlled temperature or humidity, secure segregation, permanent utilities, durable washable surfaces, or stronger GMP integration. Softwall rooms are usually less expensive and easier to relocate, but they provide less environmental and pressure control.
A successful hardwall cleanroom project therefore starts with process requirements and ends with measurable acceptance criteria. Define ISO class, HVAC performance, pressure, materials, utilities, and validation before requesting final quotations; that approach produces a cleaner supplier comparison and reduces costly design changes after construction begins.
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We'll call you
In order to serve you better, if you could kindly send an e-mail to nick@biogreenness.com for questions and details.
