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HPS heat management in cold garage DWC

Millie751

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Oct 8, 2025
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I'll be setting up my winter DWC run in a cold garage grow room, sticking with my 600W HPS to utilize the heat and save on a space heater. Currently, I run my lights at night for a consistent 78F air temp, with the res at 68F. However, I think I might have a problem when the deep winter freeze comes. My main challenge will be managing the drastically colder intake air and balancing the necessary fan speed to prevent overheating from the HPS while still retaining enough warmth for the dark cycle. Should I insulate my intake ducting, let the lights on temp run slightly higher to build a buffer for lights off, or just invest in a low-wattage tube heater for the dark period? I'm keen to know your tips on optimizing ventilation and temperature control with HPS during extreme cold. Thanks!
 
I'll be setting up my winter DWC run in a cold garage grow room, sticking with my 600W HPS to utilize the heat and save on a space heater. Currently, I run my lights at night for a consistent 78F air temp, with the res at 68F. However, I think I might have a problem when the deep winter freeze comes. My main challenge will be managing the drastically colder intake air and balancing the necessary fan speed to prevent overheating from the HPS while still retaining enough warmth for the dark cycle. Should I insulate my intake ducting, let the lights on temp run slightly higher to build a buffer for lights off, or just invest in a low-wattage tube heater for the dark period? I'm keen to know your tips on optimizing ventilation and temperature control with HPS during extreme cold. Thanks!
I wouldn't worry about insulating the intake ducting, that's too much hassle for minimal gain. the best you can do is adjusting that lights on temp buffer.
Try letting your air temp run slightly warmer, maybe 80°F or 82°F, during the light cycle. This over temp allows the tent materials and reservoirs to soak up more heat, giving you a bigger buffer when the lights go out.
If that 68°F res temp drops too much overnight, that's when you bring in a small submersible aquarium heater
it's way more efficient than a space heater for keeping the roots happy
 
hi @Millie751 the lights off drop is your biggest threat. Forget running the HPS hotter, you'll cook the canopy. Invest in a low wattage tube heater connected to a thermostat. They are extremely energy efficient and perfect for maintaining the ambient temp only during the dark cycle
 

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