How to Cool a Grow Tent without AC?

One way to cool your grow tent without AC would be to use oscillating fans, exhaust fans, and evaporative coolers. These are cheaper to run than an air conditioner.

But that’s not all! If your grow tent uses HPS or MH lights, I suggest ditching them for LEDs, air, or water-cooling lights. Led lights produce less heat than all other types of lights. Other effective cooling methods include:

  • Ensuring better insulation
  • Opening the doors
  • Raising the lights
  • Installing a light mover
  • Using a bucket of ice

Read on to learn more about how to cool a grow tent without AC and the causes of overheating issues.

What Causes a Rise in Temperature in the Grow Tent?

Before you learn ways to cool grow tents without AC, you should first determine the causes of the rise in temperatures. I will tell you just below.

Excess heat producers

Older grow lighting solutions like High-pressure sodium vapor (HPS), and metal halide (MH) lamps tend to create more heat. The ballasts of HID lights also produce a significant amount of heat, causing increased temperatures inside the grow tent.

Improper insulation

Placing your grow tent in a not-so-insulated location may cause a rise in temperatures. Now, based on different cool grow tent instructions, you should keep your tent away from direct sunlight.

Poor ventilation

A poorly ventilated grow tent will not permit heat to escape or let in much cooler air. As a result, the temperatures inside the tent will soar rapidly.

High humidity levels

Another reason behind increased temperatures in a grow tent is high humidity levels. When the humidity is high, the warm moisture stays inside the grow room, making it feel super-hot.

How Hot Is Too Hot For a Grow Tent?

Too Hot For a Grow Tent

It all depends on what plants you are growing inside the tent. Different crops have unique temperature requirements. However, most plants will thrive in temperatures between 65- and 85 degrees Fahrenheit.

If the temperatures go a little above, your plants may not experience serious issues. But if the temperatures rise above 90 degrees Fahrenheit and stay there for extended periods, this may slow their bud growth.

How To Cool a Grow Tent Without AC?

Perhaps the most efficient way to cool your grow tent is through an air conditioner. Unfortunately, the cost of using AC for grow tents is relatively high. So, below are methods to cool a grow tent without using AC.

1. Ensure Proper Insulation

One way to ensure good insulation is to place your grow tent away from direct sunlight. Another thing would be not to put the tent under a hot roof or a south-facing exterior wall. With this in mind, you should consider relocating the grow tent, probably to the basement or your garage.

Alternatively, you can use thermal bubble foil or roll on the walls, roofs, and floors of your grow space. Although expensive, this solution helps keep the grow room cool in summer by reducing up to 96% radiant heat.

2. Ditch Your Mh and Hps Lights

Mh and Hps Lights

All lights generate heat. However, HPS and MH operate at exceedingly high temperatures of around 5400-degree Fahrenheit. In addition, a 1,000W HPS light produces about 3,617 BTU of heat per hour, which is a lot.

On the other hand, LED lights boast a maximum operating temperature of about 140-degree Fahrenheit. This means LED lights are more efficient than their MH, HPS, and HDI counterparts. Therefore, you can expect them to release less heat into your growing space, keeping it cool.

3. Maximize Your Venting System and Lights

There are many ways to maximize the venting system of your grow space, like leaving the door half open. Another way would be to leave the ventilation holes uncovered to allow heat to escape and cooler air to come in.

Additionally, I recommend using an exhaust fan to vent the excess heat out of the room. You should combine this with intake fans to help replace the air inside the grow tent with fresher and cooler air. For the exhaust fan, simply place it at the top of the tent while the intake fan should be at the bottom.

4. Optimize the Grow Lights


Grow lights produce a lot of heat which can lead to overheating issues in the tent. One way to deal with this problem would be to raise your lights temporarily by about 8 to 10 inches. This can help cool your grow tent due to minimal direct heat on your crops.

Another way of optimizing the grow lights is running them at night. This is because it is cooler at night than during the day. Therefore, heat from the lights will not cause temperatures inside the tent to rise.

Furthermore, I suggest using a light mover to move the grow lights backward and forwards over your plants. This allows heat to be dispersed over a larger area, enabling the crops to rest and cool off.

5. Use Evaporative Coolers or Air/Water-Cooled Lights

Also referred to as swamp coolers, evaporative coolers are designed to chill the grow spaces through the evaporation of water. Typically, these coolers work by taking hot air before running it over a wet pad. As a result, water changes into a vapor, cooling the hot air inside the tent. For the best results, I suggest you place the cooler outside the tent.

Moving on, you should consider investing in growing lights with built-in air- or water-cooling systems. An air-cooled light allows heat generated by your HPS lamp to be removed through a duct fan, keeping your grow tent cool. On the other hand, water-cooled lights transfer heat from the LEDs via water to where it can be cooled.

6. Enhancing Air Circulation

Oscillating Table Fan

An oscillating fan helps circulate air around the plants inside your growing space by creating an artificial breeze. This breeze is what helps cool down the grow tent. To ensure maximum air circulation, I recommend placing the fan at the centermost point in your tent. However, if your growing space is big in size, you will need several fans.

7. Using Ice or Water Chillers

This is perhaps the most cost-effective way to cool your grow space than using AC for grow tent. You just find a bucket and fill it with as much ice as possible. Then, put the bucket inside the tent until it is cool enough. This method works best when combined with an oscillating fan.

Besides dry ice, you can also use water chillers to maintain the ideal water temperature. This device is built to vent heat from the grow space and dehumidify the air.

8. Keeping Humidity under Control

Another way to cool a grow tent in a garage without AC is to keep the humidity levels low or under control. In this case, I suggest you use a dehumidifier since an air conditioner is not an option. A dehumidifier pulls moisture from the air inside the grow space, thereby reducing the amount of water vapor in the air. As a result, this helps cool down the tent.

9. Make Use of Smart Pots

Smart pots are made of a breathable fabric like polypropylene to keep the roots of your plants cool. You see, containers made of plastic or clay materials only allow circulation at the surface. However, smart pots promote airflow throughout the vessel while also preventing overwatering. Consequently, this helps prevent your crops in the grow tent from overheating.


Now you know how to keep your grow space from overheating without using a cool grow tent air conditioner. So, let us look at some frequently asked questions.

How Can I Cool My 5×5 Grow Tent?

A simple air fan installed in line with the ductwork of your grow room is an effective solution. It works by venting heat from the inside of your grow space. Just be sure to get a 6-inch big fan with about 400 CFM for the best results.

Should You Leave The Vents Open In The Grow Tent?

Yes, if you are trying to cool your tent. In this case, you must also leave the windows in the tent open to allow cool fresh air to replace the vented hot air.

Why Do You Need to Cool a Grow Tent?

When it is too hot inside the grow room, your plants may suffer from wilting, root rot, and nutrient burn. Also, too much heat causes spider mites, increased stretching, and white powdery mildew.


A grow tent may overheat, especially during summer, because of using too many heat producers, poor insulation, or even improper ventilation. If you notice the temperatures in your grow space are above 85 degrees Fahrenheit, this calls for immediate cooling.

Nothing to worry about. I have mentioned many ways on the topic of how to cool down grow tent without ac. For instance, you could use LED lights, evaporative coolers, oscillating fans, ice boxes, water chillers, or LED lights.

Please follow and like us:
Pin Share

Leave a Comment

Follow by Email