In general, plants respond best when grow-room air temperatures are maintained in a range of 75 – 82F during the light cycle, followed by about a 15 degree drop in temperature during the dark cycle. Additionally, to ensure replenishment of carbon dioxide being consumed by the garden, and to moderate humidity levels, a fresh air ventilation system should be rapidly replacing total air volume. A healthy humidity level ranges from about 45 – 55%. Levels higher than these create an atmosphere conducive to the growth of harmful fungus/powdery mildew.
To accelerate the process of photosynthesis, and hence achieve accelerated growth rates and exceptional yields, some growers opt to create an artificially enriched CO2 environment by introducing compressed CO2. But in order to realize the full benefits, the grow-room should be sealed to consistently maintain in excess of 1,000 PPM of CO2 in the atmosphere, and equipped with air-conditioning and dehumidifier systems to sufficiently compensate for the lack of fresh air ventilation.
In the absence of this costly equipment, CO2 enrichment can still be effective with a fresh air ventilation system. However, grow-room ventilation must be suspended at regular intervals while CO2 is being introduced into the atmosphere to allow for maximum plant absorption via leaf respiration.
So in simple terms, the message is that your high-value garden will flourish in an environment of moderate temperature with gentle/breezy air movement that’s rich in carbon dioxide content.
In summary, keep in mind that each grow-room has its own set of environmental variables, making definitive instructions problematic. But for the most part, grow-room conditions within these “Gardening Guidance” parameters will allow plants to efficiently utilize nutrients and optimally conduct photosynthesis.