Regardless of lighting technology, the transpiration of the plants makes up most of the latent (moisture) load. Plants will give off roughly 90% of the water they take in through their root system back to the ambient space. Plants however do not take in all the water that is provided to them, typically there is at least 10-20% that dissipates through runoff.
When plants transpire there is an evaporative cooling effect. For every pound (16 Ounces) of water that evaporates, 1,040 BTU’s of evaporative cooling occurs. This evaporative cooling effect is present during lights on and lights off. During lights on there is also a large sensible load from the lights, but during lights off the load is latent dominant, and the evaporative cooling effect necessitates additional reheat to maintain target temps within the room.
Desert Aire's sizing and load calculation software takes the evaporative cooling effect from transpiration into account. In addition, we have developed a sophisticated multi variable algorithm that can calculate the specific transpiration rates of the plants based on a host of inputs including lighting type and density, growing media, watering strategy, and C02 supplementation rate.
Learn more about determining the sensible and latent loads of indoor farms in our Application Note 25: Grow Room Load Determination