Temperature Controlled Greenhouse Systems
Crops grown in controlled conditions produce more, and higher-quality, product year-round. Here’s what that control actually involves.
Why Temperature Control Matters
Every plant has an ideal temperature range where it carries out photosynthesis and other metabolic processes as efficiently as possible. Providing cover with a greenhouse doesn’t guarantee that range on its own — most growers still need to heat or cool the air to hit their target, and how much depends on climate, topography, and crop variety.
How to Regulate Greenhouse Temperature
Heating methods include ground heating, table heating, and heat pipes, with many modern greenhouses using combined heat and power (CHP) systems to cut energy costs. Thermal screens are another common addition — they trap heat inside the greenhouse, reducing how much additional heating is needed.
On the cooling side, growers typically rely on HVAC systems, or wet pads and fans. Because temperature and humidity are inextricably linked, how you heat or cool a space should always account for humidity too.
Humidity Control in Greenhouses
Plants have an ideal relative humidity range, just like they do for temperature — it lets them metabolize, develop, and bear fruit while staying healthy and strong.
When Humidity Is Too Low
In dry conditions, plants transpire excessively, causing water stress — a state where the plant slows or stops critical processes to conserve water. Misting systems or wet pads can inject water vapor back into the air to raise humidity when it’s too dry.
When Humidity Is Too High
High humidity is far more common in greenhouses, since plants are constantly transpiring. When the air becomes saturated with water vapor, transpiration becomes physically impossible — the plant is forced to slow its metabolic processes, since it can’t move water. High humidity also drives disease and mildew outbreaks; downy mildew and gray mold both need high humidity to establish, and once they do, they’re difficult to stop even if humidity returns to normal.
Controlling Greenhouse Humidity
Ventilation is the traditional fix for greenhouse humidity, but it only helps when outside conditions cooperate — rain, humidity, or cold outside (often overnight) limit how much it can do. Even when it works, ventilation can be costly, since it releases air that already contains heat you paid to generate, forcing growers to keep heating while expelling warm air and pulling in cold air.
Dehumidification is the more complete answer. Dehumidifiers use controlled condensation to physically remove water vapor from the air, working independently of what’s happening outside. For a deeper look at balancing ventilation against other climate tools, see our guide on air circulation vs. natural ventilation.
Greenhouse Lighting and Its Effect on Climate
Lighting, or radiation, directly affects how well plants photosynthesize, develop, and grow — but sunlight isn’t always consistent, so greenhouses often use supplemental grow lights to fill in on gloomy days or extend daylight hours. Some plants (cannabis among them) are photoperiodic, meaning they need very specific light and dark cycles to bloom, which is why many growers use blackout screens to control dark periods precisely.
Radiation, including UV, also raises both temperature and plant transpiration rates — which in turn raises humidity. Getting greenhouse climate right means balancing all of these factors together, not tuning one in isolation.
Managing Greenhouse CO2
Beyond temperature, humidity, and light, greenhouse growers can enrich the air with additional CO2 — a key ingredient in photosynthesis and assimilate production. CO2 enrichment helps plants grow faster, but it has to be balanced against light levels, since plants need more light to benefit from the CO2 boost, and more light raises temperature and humidity in turn. Changing any one of these four factors affects the other three.
Monitoring and Automating Greenhouse Climate Control
The best way to hold ideal conditions is to spread multiple monitoring devices throughout the greenhouse rather than relying on one reading — a single thermometer or humidity sensor can miss the fact that one part of the greenhouse is dry while another is humid. That kind of inconsistency is one of the most common causes of uneven plant growth and disease spread, since disease can take hold in one pocket and spread to plants that were otherwise in good conditions.
Once a grower has reliable monitoring in place, automating the response is the next step. A controller like the Captain can be set to start dehumidifying automatically once relative humidity crosses a set threshold — heating, cooling, lighting, and CO2 enrichment can all be automated the same way. That combination of monitoring and automation is often the difference between a greenhouse that’s profitable and one that’s fighting disease and high production costs all season.
Ready to Automate Your Greenhouse Climate?
Improving climate control in your greenhouse means fewer diseases, better plant growth, and real energy savings. If you want to get more out of your greenhouse, contact us and we'll talk through the right environmental control setup for your operation.