Hello

Place silica gel packs or calcium chloride in enclosed areas (e.g., near trays) for localized humidity control.

Seal leaks: Ensure the room is airtight to prevent external humid air from entering.

Install an energy recovery ventilator (ERV) to exchange air while conserving energy or Use a dedicated grow-room HVAC system with integrated humidity control.

Is the room specifically set up as a phytotron, or is it just an office with lights and an air-conditioner? It might require different solutions depending on which you have.

It sounds like you need some sort of air exchange mechanism, to remove humid air as fast as it is produced. That will likely affect the air conditioner, which will be working harder to cool (or heat) the replacement air. Or look for a dehumidifier unit, which will work continuously rather than the silica gel packs suggested above.

Perhaps you should consult an HVAC expert (heating cooling air conditioning). A dedicated grow room might be able to control that better than the office setup.

If you can't manage the air, perhaps you can manage the water: Can you isolate the substrate the plants are growing in from the atmosphere with impervious sheeting or perforated covers or something like that?

Or reduce the water component by using polyethylene glycol to create a high water potential deficit in the substrate. I used to have an empirical equation for PEG10000 where a known soil water potential could be created with a specific concentration of PEG in water, but I don't have it to hand. I'm sure you can google up something similar.

Thank you very much for your answers Faiegh Akhkandi and Matthew Wheal !

My setting is a room with lights and airconditioner, well isolated. I live and work in southeast Brazil, so the climate is hot and humid in this time of the year. I'm inclined to try the silica first and then a dehumidifier unit.