How to Cool a Grow Room Cheaply

Written by melissa worcester
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How to Cool a Grow Room Cheaply
Keep your grow room from getting too hot. (grow children image by Yuriy Rozanov from

Grow rooms can become too warm because of heat given off by the lights, and they can also get hot just because of the surrounding air temperature. Just like with your house, there are ways to cool it that don't cost a lot of money.

Skill level:
Moderately Easy

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Things you need

  • Insulation, and tools and materials for installing it
  • 2 exhaust fans, ductwork if necessary, and tools and materials to install
  • Timer (optional)

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  1. 1

    Insulate your grow room. This is especially important if the grow room is outside or if it is in a location where the surrounding air frequently gets hot. There are many kinds of insulation; which you choose depends on the shape, size and construction of your room and on your budget. Buy rolls of fibreglass insulation and install it between the studs, then cover it with plastic, drywall or particle board. You can also spray foam insulation into cavities between drywall or plywood. This is a good method if your walls are already in place. Cut a small hole in the drywall and spray in the insulation, then cover or patch the hole. Do this for each cavity (between each of the studs).

  2. 2

    Install exhaust fans. Place one fan at the top of a wall or in the ceiling, blowing outward. This fan will remove the hot air from the room. Place the other fan low down, at the base of a wall (opposite from where the top fan is located, if possible) and aiming so that it blows air into the room. To install fans, cut a small hole in the wall. Reinforce the edges with wood, or cut the hole near the wood framing. Attach the fan to the wood with screws. If the surrounding area is a room that can become quite hot, consider running ductwork to the outside. If you don't want to run ducts to both fans, opt to provide them for the lower fan first. Provide a source of electricity.

  3. 3

    Set the fans on a timer or a thermostat. The timer is the least expensive and easier of the two options. Observe the room around the clock to note the temperature in both the room and the surrounding area (or the outside, if the room is outside or if you attached ductwork to the intake fan). Set the timer to turn on when the outside air is cooler than the air inside the room, and to turn off again when the outside air is hot. For most areas, that will probably mean running the fans at night and turning them off in the morning, but this will depend on time of year, location of the room and the climate of your area. Adjust the timers as the seasons change. You can also attach a thermostat that measures the air temperature inside the room and turns the fans on when it reaches a certain temperature.

  4. 4

    Provide shade for your room. If the room is in a basement or attic, cover the windows to keep sunlight out. If the room is outside, consider moving it to a location where there is natural shade from trees or a nearby building, especially in the afternoon. Purchase an awning or rig up some shade with a vinyl dust sheet to keep sun from hitting the room if it is built outside.

Tips and warnings

  • Always run both fans at once. The principle is this: you are removing the hot air, aided by the fact that hot air rises, and replacing it with cooler air from outside. This is why you don't want the fans running during the really hot part of the day, unless the temperature in the room is still warmer than the outside air at that time.

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