Grow Room Temperature Too High- 8 Cooling Solutions [+ 3 Bonus]

“It’s too hot inside the grow room, and the dying plants are soon going to freak me out!- What can I do now?”
– A Random Grower

I know from you visiting this webpage that, you’re recently worried about this very same problem. Maybe the grow room temp is 85, 90 or even 100 degrees. And all of your hard works of setting the entire grow system is about to go in vain if you don’t do something that really works.

Don’t worry. Every grower had faced grow tent heat issues once in a while. And some of them had made their way out, including me. And I am going to share the exact ways to solve the issue immediately.

So, what you need to start with?

Long story short- you can do things right away to beat the situation-

  • To cool the grow room down
  • To do something that will stop high temperature from reaching trouble to your plant’s health.

For both of the processes, you need to know how many ways are there, and how exactly they work. And that’s all we’re going to talk about today. Keep reading.

High Temperates Kills the Plant. Here is How-

What exactly happens when you grow room temperature is too high? Here is the answer-

Temperatures do affect a plant’s ability to photosynthesize, seed germination and fruit/flower development. Which all together, upset you with less and low-quality yield.

To break it down, here are some basics about high temperature in growing space-

First thing first, grow lights are heaters. LED, HPS, Fluorescent, Plasma and anything else we can name, are nothing but light emitting heaters. And when you’re leaving the grow room with all lights switched on, you’re basically letting the heaters to heat up the grow room.

A high temperature of a grow room directly affects is the leaves and roots of plants. Here is how-  

Plants cool themselves by passing water through little holes on the leaves, called ‘Stomata’. While water vaporized through Stomata, it takes heat from the leaves and cools the plants down. The process is called Transpiration.

Hot temperatures and conditions activate the guard cells around Stomata while water is passing through it. And that also causes stress on the root system of the plant.

This eventually shuts your plants down with no photosynthesis. That’s a pretty touch condition for any plant, right?

How to Detect ‘Too High’ Temperature of Your Grow Space?

A perfect grow room should have 70-80°F (21.1-26.6°C) of uniform temperature. What I mean by ‘Uniform’ is, it should be the same throughout the entire contour. As the temperature around the sources(lights) are higher, you can use oscillating fans to move the air around.

However, that’s the generalized temperature range for fast growing annuals. A little more of the temperature may be good also, as long as you have something like a water chiller to protect the root zone.

To be more certain about if the temperature is too hot for the plants or not, check for any of these bad symptoms in them-

  • Plants stop growing or grow tall and leggy.
  • Flower don’t form properly.
  • Essential oils are lost.
  • Fruits bort prematurely.

However, it’s always better to detect a bad temperature and environment before letting your plants to wilt. A good kit can be a 3-in-1 Moisture, Light and pH meter. Here is a popular one from Healthy Wiser.

Anyways, to be straightforward, we’re about to consider anything more than 85°F or 90°F high and going to look for the solution throughout the whole article.

8 Actionable Grow Room Cooling Solutions

Now we are at the heart of the article, just what you need badly right now. Here is the list of 7 easy and effective instant solutions for high grow room temperature-

1 of 7: Boost Up the Air Exchange Rate

Hot air accumulates rapidly in indoor grow space. To take this hot air out, you might have occupied an input and extractor fan in it. To give a boost to the air exchange rate, crank up this fan duo.

You can regulate the fan speed manually every now and then, but there are tools that can do it automatically, and accurately. My favorite is the newly released Titan Controls Kronus 4.

One more effective tips to have a better and cooler air exchange is to collect the input air from the coolest place available nearby. I’ve seen growers put an air conditioner to cool the input.

2 of 7: Have A Low-Strength Nutrient Solution

A hot temperature induces more water through the leaves, resulting in a higher consumption of water of roots. Which forces them to intake more nutrients whatsoever.

And a higher consumption of nutrients come with a risk of toxicity issues of plants. Which eventually leads them to death.

Not to let it happen, dilute the nutrient solution by a certain percentage(20% in most cases). Adding the measured amount of pure water is all you need to do.  The keep the solution consumable, keep it well-agitated by adding an air pump and some air stones in it.

3 of 7: Enhance Air Flow

Air is the medium that conducts heat from the heat sources to the plants. So, if there is a way to ensure stronger air circulation around the tent-inside, the effect of heat will deduce.

Using an Oscillating Fan is the best way to get it done. Place it in a way that it can circulate air in almost every corner of the room, especially the air between the heat source and plant canopy.

Here are two of my personal recommendations-

4 of 7: Enhance Humidity

Humidity is the very obvious thing that comes next to temperature in any discussion. And vice versa. They affect each other and you can deal with the risen up temperature of a grow space by controlling the relative humidity of it.

Now, how to keep your grow tent cool by controlling humidity?

According to A Study from Sciencing, if the temperature rises in a contoured space, the relative humidity decreases. If you’re dealing with an unusually high temperature in your grow room if you find the relative humidity low as well. If it’s down to 60%(In vegetative mode), or 40%(In flowering mode), it’s urgent to increase the humidity level.

Now, here is the fun fact-

While you’ve to increase the humidity level to save the plants from drying up, it will also cool down the plants as well. Remember the ‘Vice versa’ fact? Increased humidity comes with decreased, and that’s how it works in your favor.

An advice is, use a good quality humidifier, and an automatic controller to make it efficient.

5 of 7: Switch Off or Dim A Few Light Sources

Many of us growers think that raising the light sources up from the plants will solve this temperature problem. But the truth is, this may decrease direct heat on the plants by a little, but not the temperature of the entire grow tent.

What works in reality is- switching off half of your light sources for a while. If you have two, you may turn one of them off for a while, and that won’t be a problem.

If you want to move one step forward, you can get a dimming function like Galaxy Grow Amp Ballast. It works best with HPS lamps.

Note: To avoid any heat issues that generates from light sources, learn how to find the correct wattage of lights for your indoor plants.

6 of 7: Chill The Nutrients

If you think that your plants can withstand a high temperature by any mean, you’re wrong. Almost any grow room plants can withstand 90-100°F and even higher temperature.

In case you don’t find any quick solution to control the temperature(living in a hot area), and still want a maximum yield, you better chill down the nutrients to a temperature of 55-65°F.

To make sure that the temperature of nutrients doesn’t get high again, you need to use a pump that circulates the nutrient solution. An aquarium chiller is the best tool in rescue.

7 of 7: Using Air Cooled Hoods

Light sources and the heat emitted from them is the biggest culprit behind an increased temperature of your grow room. So why don’t you use an air-cooled reflective hood? It’s something that will remove up to 50-60% of the heat generated by grow lights.

There are models like Magnum XXXL that takes a good cut the heat from the light source away. They’re sealed and can be added to the duct fittings as well. If a duct hose of 6″ is connected with the hooded light, it will certainly lower the temperature inside the grow room.  

3 Bonus Tips

I’m sure that working on a few of the aforementioned tips will decrease the excessive temperature or help your plants survive in a hot temperature anyways. On the top of these tips, here are some bonuses

  1. Run the lights at night

    Although we all are aware of the fact, I insist on it more because it will keep the ambient temperature low.   

  2. Seal the entire space up

    If you’re a grower living in a hot climate area, this might work even better for you. Such a grower is more likely to keep it cool with an air conditioner and a carbon-di-oxide generator.  It’s better to use an underground space, as it provides a natural insulation. Side Note- Plants of a grow space can tolerate high temperatures with an elevated Carbon-di-oxide ppm.

  3. Toughen up Cell Walls of the Plants

    This will help in the better survival of plants, and also to colonize the root zones of plants.    The key to such toughening is a good quality Silica Supplement for plants. Currently, I found this one from Botanicare very effective.  

John Terry

Hi, John Here! When I'm not busy working at my own startup, you may find me roaming around my indoor plants, playing CoD with my wife and kids, or hanging out with pals.

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