Temperature, Humidity & CO₂ in the Grow Room
As the colder season begins, the plant setup moves back indoors: Now is the ideal time to optimise your indoor climate. In a well-tuned grow tent or grow box, temperature, humidity and CO₂ levels largely determine how vital and resilient plants grow.
Those who control these factors can unlock the full potential of modern LED lighting systems – with stable conditions, lower energy consumption and consistent growth.
Why Climate Is Crucial in Indoor Growing
A consistent climate supports nutrient uptake, prevents stress and helps avoid problems such as waterlogging, mould or drought damage. Even slight fluctuations can slow the development of sensitive plants.
With precise climate control you achieve:
- consistent growing conditions
- controlled air circulation
- stable temperatures despite heating periods
- reduced risk of fungal or pest infestation
Temperature – The Foundation of a Healthy Plant Room
The ideal temperature range for indoor cultivation is 24–28 °C under light and approximately 20 °C during the dark phase. During the winter heating period, the incoming air can often be too dry or too warm – which is why using exhaust and intake systems with adjustable controls is worthwhile.
Recommended:
- Thermo-hygrometer with min/max memory
- Fan with temperature controller for consistent fresh air supply
- Insulated air ducts to prevent heat loss
Humidity – Balancing Growth & Protection
Relative humidity (RH) affects evaporation and nutrient uptake. In winter, it frequently drops below the ideal level due to heated air.
Optimal humidity by phase:
- Germination → 70–80 %
- Growth → 60–70 %
- Maturation phase in botanical models → 40–50 %
(Note: this value is intended solely for general scientific classification and does not constitute cultivation-related guidance)
With a humidifier or dehumidifier with an integrated hygrostat, the climate can be precisely controlled. Climate controllers that regulate temperature and humidity together are particularly effective.
Tip: Regularly check the VPD value (Vapor Pressure Deficit). If it is between 0.8 and 1.2 kPa, plants transpire optimally – neither too strongly nor too weakly.
CO₂ – The Underestimated Growth Factor
CO₂ is essential for photosynthesis. In enclosed spaces, CO₂ levels can quickly drop below 400 ppm.
A target value of 800–1200 ppm is considered optimal for balanced plant growth.
Solutions for CO₂ control:
- CO₂ bags or pads: simple, low-maintenance supplement for small spaces
- Digital CO₂ controllers: with sensors and automatic regulation
- Circulation fans: for even distribution throughout the entire tent
Components for a Stable Indoor Climate
A professional setup consists of:
- Fans & exhaust systems – regulate temperature & fresh air
- Activated carbon filters – for clean, odour-neutral exhaust air
- Climate controllers – automate temperature and humidity values
- LED grow lights – efficient & heat-optimised
- Measuring devices – thermo-hygrometers & CO₂ monitors
Conclusion
Especially in late autumn and winter, a well-regulated climate is crucial for keeping plants healthy through the cold season. With precise control of temperature, humidity and CO₂, you create ideal conditions – regardless of external influences.
At the Schall & Rauch Hanf Fachmarkt you will find suitable solutions for every setup: from digital hygrometers and fan sets to climate controllers for fully automated systems.
Tip: Monitor your climate regularly – small adjustments in winter bring great stability throughout the entire growth cycle.