How to Cool Down your Grow Room

Image used courtesy of Quinn Dombrowski

The last time I covered hydroponics, I talked about general air circulation and how important it is to keep a breeze cycling through your grow room.  With the sizzling hot month of August looming ahead and the summer heat adding up, the dangers of excess heat from lighting and improper ventilation in your grow room can become extremely dangerous to your plants.  But can you actually do anything about the annual heat wave?  Take a look below for some helpful tips on how to stay frosty and keep your plants cool.

 Air Circulation

In line Ventilation Fan

Hurricane Afterburner Fan

As I said before, ventilation is a key player.  Proper air circulation lets you move cool air into and hot air out of your grow room.  Avoid twisting ventilation ducts – on average, the loss of air movement in a single 90-degree turn is equivalent to the loss over 20 feet of ducting – and place your air intake at ground floor on one side of the room.  Place the exhaust fans near the ceiling at the other end.  This improves circulation into the room and pulls the cooler ground air into the room while the hotter air rises and escapes through the top.  The goal is to replace all of the hot air with cool air (as a bonus you replace the stale air with fresh air).  If things are still too hot, you can always try air conditioning the room; though this has a tendency to dry out the room.  You can also cool the air in the room your intake is pulling from to indirectly cool your grow room.

Pro Tip:  You want to be able to completely replace the air in your room within five minutes.  To do that you’ll need to know what kind of fans you need.  Multiply the length of the room by its width and height (in feet) then divide by five (minutes) to see how many CFM of air (how much air can be moved by the fan in cubic feet per minute) you’ll need.  As an example:  A 10x10x10 room would be 1000 cubic feet.  To clear the air you will need a CFM rating of at least 200 to replenish all of the air in five minutes.  Since you always want to account for filters and turns; a 500-CFM fan would guarantee total air circulation in less than 5 minutes.


LED Grow Lamp

SolarStorm LED Grow Light

Let’s assume you have the perfect ventilation system for your plants and the room is still too hot.  Obviously, the largest source of heat in a grow room comes from lighting.  So, if you live in a constantly hot climate the best thing would be to switch to LED or fluorescent grow lights.  They release very little heat and technological advancements have made them pretty much equal to HPS and MH lamps.  But if you’d rather save on the upfront cost there are a few other methods you can use.

  • Run your lights at night.  Everything is cooler at night so it becomes much easier to maintain cool temperatures.  For this you’ll want a timer to make sure your plants still get the right amount of light each night.
  • Use fan and temperature controllers.  Temperature sensors and controllers can be used to turn on extra fans or shut off lamps completely when the internal temperature of the room rises above tolerance.
  • Use a dimming ballast.  While this will decrease the overall amount of light in the room, a dimmable grow lamp means you can control its heat output without completely shutting off the lamps.
  • Air-cool the lamps. Directly cool your lamps with a separate ventilation system.  Use a sealed hood for your lighting and run additional ducting to directly cool the lamps (as a bonus, place dry ice above your lamps to help cool them and add CO2 to your grow room).


Improper ventilation and the heat from lighting are the biggest problems when it comes to excess heat.  For your plants you’ll find that better fans, newer lamps, and a few climate control tips can give a refreshing break to the summer heat.  For you, you’ll want a tall glass of lemonade while you’re working.  We’re based in Texas so we’re no strangers to hot days.  But what do you do to keep your plants cool (or even just stay refreshed yourself) throughout the year.  Does it even get hot enough to worry about?  Let us know in the comments or give us a shout on FacebookTwitterGoogle PlusLinkedIn, or Pinterest!

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Will Parsons

Will is a Copywriter for 1000Bulbs.com. He has a background in small-farm agricultural hydroponics and electrical engineering, with degrees in applied engineering and emerging media. Previously he has worked in renewable energy and green technology fields. His own interests are for creative writing and storytelling and he tends to be an early adopter of new technology. Enjoy new stories alternating between lighting and hydroponics each week.