Lithium-ion battery manufacturing places extraordinary demands on facility engineering, and nowhere is this more apparent than in the design of clean & dry rooms. These specialised environments must simultaneously control airborne particulate contamination and atmospheric moisture, since even trace amounts of either can compromise cell performance and safety. Understanding how HVAC systems are engineered to meet these dual requirements is essential for anyone involved in gigafactory construction.
Why Moisture Control Matters
The manufacturing process for lithium-ion cells generates minute metallic particles that float within the flammable, lithium-containing liquid housed inside each cell. Separators keep the anode and cathode apart, but should a fragment of metal breach that barrier, a short circuit can result. Depending on how the fault develops, this can trigger a fire if a spark ignites the liquid, cause an explosion if internal pressure rises rapidly, or lead to melting and leakage if the temperature climbs more slowly. Because of these risks, clean & dry rooms are engineered around simple psychrometric principles: delivering a predetermined volume of air to the space at a set dewpoint, then ensuring no moisture infiltrates that air once it leaves the desiccant wheel.
Achieving the Right Dewpoint
The relationship between relative humidity and dewpoint is central to dry room performance. A dewpoint of minus 20 degrees Fahrenheit corresponds to 2% relative humidity or less, minus 30 degrees to 1% or less, and minus 40 degrees to half a percent or less. This dewpoint is achieved by controlling the speed of air passing across the desiccant wheel, which in turn dictates the volume of air that can be processed. Engineers must also account for every load acting on the room, including occupancy, airlock infiltration, make-up air requirements, envelope openings, and vapour transmission through the building fabric itself. Each of these factors carries its own engineering calculation, and none can be overlooked if the target dewpoint is to be reliably maintained.
Cleanliness Alongside Dryness
Beyond humidity control, clean & dry rooms must also satisfy cleanliness classifications, with certification typically required to ISO 14644 standards. Achieving this alongside dryness means increasing airflow, incorporating additional return paths to maintain cleanliness at work surfaces, and favouring ceiling-mounted filtration as the final filtration stage rather than relying solely on central air handling. Horizontal protrusions that encourage particle accumulation should be minimised wherever possible.
Design Principles for Effective HVAC
Several practical principles underpin successful dry room HVAC design. Make-up air should be preconditioned with cooling before desiccant drying takes place, reducing the load placed on the drying equipment itself. The building envelope should be extended to incorporate the air recirculating function, while duct distribution should enter the envelope buffer zone immediately after discharge from the drier, limiting opportunities for moisture ingress along the way. The return side of the air system can then serve as a buffer zone for supply air, and the drying function should be kept separate from the cleaning function to allow each to be optimised independently. Cleanliness levels can also be monitored and varied according to the specific process step underway, rather than applying a single fixed standard throughout.
Envelope and Ductwork Considerations
None of this is achievable without an airtight, moisture-resistant envelope. Panel junctions must be sealed to prevent vapour transmission, and the vapour barrier must be maintained independently of building movement. Materials prone to holding moisture or cracking over time should be avoided, and every penetration made by any trade must be carefully sealed. Ductwork should be welded or otherwise built to minimise leakage, with a buffer zone provided for interstitial areas and continual inspection built into the maintenance schedule.
Well-designed clean & dry rooms are therefore the product of careful, integrated HVAC engineering, balancing humidity control, particulate cleanliness, and envelope integrity to protect both product quality and operational safety in gigafactory environments.
For the opportunity to have in-depth discussions about this and other challenges facing gigafactories, meet with leading solution providers and network with industry experts, attend the 7th BATTERY GIGAFACTORY Summit USA: Advances in Planning, Engineering and Operations, taking place on November 18-19, 2026, in Nashville, Tennessee, USA.
For more information, visit our website or email us at info@innovatrix.eu for the event agenda. Visit our LinkedIn to stay up to date on our latest speaker announcements and event news.
