Why LED Grow Rooms Need Warmer Temperatures Compared to HPS Grow Rooms
When it comes to indoor growing, understanding the nuances of different lighting technologies is key to optimizing plant health and yield. One major difference between LED grow lights and traditional HPS (High-Pressure Sodium) lights is the type of heat they produce—or, more accurately, how they distribute it. This distinction has a significant impact on the temperatures you should maintain in your grow room.
The Infrared Heat Difference
HPS grow lights emit a significant amount of infrared (IR) heat, which directly warms plant surfaces, such as leaves and stems, in addition to the ambient air. This radiative heat mimics the warmth plants would experience from sunlight, effectively raising the "perceived" temperature around the plants even if the air temperature is lower.
On the other hand, LED grow lights are highly energy-efficient and designed to minimize heat waste. They don’t emit much infrared heat and rely primarily on ambient air temperature to keep plants warm. As a result, while the air temperature might feel similar in both grow rooms, plants under LED lights are often cooler due to the lack of direct IR warming. This can lead to slower growth, reduced transpiration, and less efficient nutrient uptake if not properly managed.
Why Warmer Temperatures Are Essential in LED Grow Rooms
Because LEDs don’t provide that direct IR heat, maintaining a slightly warmer air temperature in LED grow rooms is essential to replicate the thermal environment that plants thrive in. Here’s why:
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Improved Photosynthesis
Plants are most efficient at photosynthesis within a specific temperature range. In LED grow rooms, where plant surfaces aren't being warmed by IR radiation, maintaining an air temperature of 80–85°F (27–29°C) (compared to 75–80°F for HPS grow rooms) can help compensate for the lack of radiant heat. -
Enhanced Transpiration
Warmer air encourages higher transpiration rates, which is essential for nutrient uptake and overall plant metabolism. Cooler temperatures under LEDs can slow down this process, potentially leading to nutrient deficiencies or slower growth. -
Optimal VPD (Vapor Pressure Deficit)
Maintaining the correct temperature is key to achieving an optimal Vapor Pressure Deficit, which balances humidity and temperature for ideal plant growth. Warmer air under LEDs helps maintain the proper VPD range, ensuring that plants can transpire and absorb nutrients effectively.
Tips for Maintaining Warmer Temperatures in LED Grow Rooms
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Increase Ambient Air Temperature:
Use heaters or adjust your environmental controls to raise air temperatures slightly above what you’d maintain in an HPS grow room. Aim for a consistent 80–85°F (27–29°C) range. -
Monitor Plant Leaf Temperatures:
Use an infrared thermometer to measure the actual temperature of your plant leaves, as this is often cooler than the air temperature under LEDs. -
Optimize Air Circulation:
Warm air can distribute unevenly, especially in larger grow rooms. Invest in proper fans and ducting to ensure consistent airflow throughout the space. -
Adjust Humidity Levels:
Warmer air holds more moisture, so adjust your humidity levels accordingly to maintain a VPD range of 0.8–1.2 kPa for optimal plant health. -
Supplement with Radiant Heat:
If needed, consider adding infrared heaters to provide gentle radiant warmth similar to what HPS lights emit.
The Bottom Line
While LED grow lights offer unparalleled efficiency and tailored spectrums for plant growth, their lack of infrared heat requires growers to take extra steps to maintain the ideal thermal environment. By keeping air temperatures slightly warmer than those in HPS grow rooms and closely monitoring plant response, you can unlock the full potential of your LED lighting system.
Investing in the right environmental controls and understanding how your lighting technology interacts with your plants will ensure healthier, faster-growing crops and better overall yields.