Grow Room Cooling Techniques

My grow room or garden is way too hot. What can i do?

Wilted plant

Help Me!

Summer’s here and the time is right…for heat issues.  Mastering grow room cooling techniques in your hydroponic garden is important during the summer months because a garden can suffer greatly when heat gets out of control.  If you are among the fortunate few who live in a cool coastal climate, these tips may not be for you.  For the rest of us, here are some tips to keep your grow room cool during the hottest part of the summer.

What can you do to cool your room without an air-conditioning?

First, let’s start with the least expensive options, and go from there…

Fan Speed Controller

Fan Speed Controller

One of the best things you can do to reduce heat and save money is to run your lights at night, so you can take advantage of the cool night air to help keep your garden in the desired temperature range.  It is important to make sure you have sufficient negative pressure to pull out the hot air and replace with the cool via your intake.  As a general rule of thumb, your intake CFM should be 25% of the cubic foot per minute (CFM) rating of your exhaust vent fan.  It is important to note that the type of ducting, length, and number of turns will increase static pressure, and lessen the efficacy of your exhaust fan.  It is a good strategy to have your intake at one corner, low to the ground, and to have your exhaust fan in the opposite, top corner, close to the ceiling.  Heat rises, you know?  One trick I have seen many folks use is a router/speed controller(s) to manually adjust the speed of one’s exhaust in correlation to their light cycle; for the least expensive, manual process.  Unfortunately while dialing the speed down may not completely cool your room, it will allow you to take control of your air flow with your existing fans and mitigate the difference between a positive and negative pressure.  If you don’t have the time to make the daily changes there are a number of more advanced tools that can do it for you, from controllers to a number of techniques.

Temperature and Humidity Controller

Temperature and Humidity Controller

An important part of climate control is using a temperature/humidistat so you can keep your garden cool with the lights on, and dry with the lights off.  If you are using CO2 enrichment, you will need a more advanced climate controller. CO2 enrichment is another topic in of itself, so we won’t go into too much detail here.  The C.A.P. Air-1 or the Sentinel EVC-1 are great inexpensive analog temperature/humidity controllers.  It is important to have this basic functionality in your garden.  A good digital upgrade would either be the Titan Kronus-1, or the Sentinel EVC-2.  Both are excellent products; however the Kronus-1 has a three year warranty and only controls temp and humidity, while the EVC-2 can control CO2 enrichment to a degree.

Vortex Inline Fan

Vortex Inline Fan

Once you have your exhaust set-up, it is time to set-up your intake.  Depending on the size of your garden, you can use a booster fan or an in-line fan.  In a bigger garden, you certainly would want to use an inline fan because they can be more powerful than traditional booster fans.  It is important to set-up your exhaust and intake properly.  Most of the books recommend exhausting the total volume of air out of your room in less than five minutes.  These days, it seems like most people are on the one to two minute program.  Based on what I’ve seen, I would say the one to two minute program is preferred if you are either in an overly humid, or hot environment.  Don’t forget the formula: length of room times width of room multiplied by height gives you the cubic foot total. You do not want your fan to have a higher speed rating than your filter.  In a 10 by 10 room with 8 foot ceilings, a 400 CFM fan would exchange the total volume of air in the room in two minutes.  A 100 CFM booster fan would be an adequate intake. When dealing with temperature and humidity, it seems it is always better to have more ventilation than less.  And remember when one adds a carbon filter, turns, and length of duct will slow down the CFM rating of the exhaust. **Please note, this formula used to illustrate a concept based upon an ideal world situation with no restricted air-flow.  Length, turns, slack, and attaching a carbon filter will reduce your exhaust considerably.  And it is crucial that these factors are not lover-looked.  To give you an idea, one 90 degree turn is like adding 20 feet of straight duct.  

Once you get your ventilation set-up properly, and everything is working swimmingly,what can you do if your grow room is still getting too hot?  You could pony up for an air conditioning for a quick fix, or you can adjust your space a little.  But as we all know, there are certain limitations that prevents an air conditioning from being a viable option.  These tips are for you. Before there were dimmable digital ballasts, and high temp shut off controllers, gardeners without air-conditioning were forced into a manual process of shutting off one or more lights to keep control of the temperature in their garden space.

Here are some viable tricks for keeping your space cool without an a/c:

  1. Air-cool your lights.  This is another topic worthy of further exploration, which we can’t go into here.  Most important thing to remember with this strategy is to make sure your hoods are sealed and try to have as few turns in your ducting as possible to achieve maximum air flow.
  2. Use dimmable ballasts.  You can dial them down when it gets hot.  Unfortunately with the limits of the current technology, this is still a manual process.  The benefit of this method versus the one that follows is that your plants get reduced light and spectral output, as opposed to no light which brings me to the next point.
  3. High Temp Shutdown

    High Temp Shutdown

    I highly recommend this! The use of a high temp shut off controller is a great tool to control heat.  Disadvantages here are one, it turns off the light completely, and if you wanted to turn off multiple lights, you would need multiple controllers.  The Titan Zephyr-2 or the C.A.P. HLC-3e are both excellent controllers that can handle this functionality.

Just remember, run your lights at night to take advantage of the cool air.  Air-cool your lights if you can.  Make sure your exhaust and intake is set-up properly.  Then, if you are still having problems, utilize dimmable ballasts or a high temperature shut-off controller to ensure maximum results.  One other caveat is that the proper use of CO2 enrichment can allow you to keep your temperature a little warmer than you would otherwise.  But this is something we will go into further detail in the future.

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