Skip to content

How to Cool a Grow Room

How to cool a grow room

Grow rooms are great for the gardener who wants to exercise their green thumb year-round. But they can be a source of frustration if they’re not planned properly. One of the biggest issues indoor growers face is temperature control.

Indoor grow rooms typically require special lights to help plants thrive. However, these lights are oftentimes very hot and, if the grow room’s temperature isn’t regulated, can cause plants to die.

To ensure your plants don’t meet this miserable fate, there are a few key pieces of cooling equipment you’ll want to invest in when building your grow room.

Grow Room Cooling Systems

Air conditioners

Air conditioners can be an excellent choice for cooling grow rooms; you just need to buy the right one. If you do decide to go the AC route, go with a mini split system, as it will allow you to maintain a set temperature in your grow room that’s separate from the rest of your home. A mini split system is also more efficient and easier to install than other types of AC systems.

When deciding how to cool your grow room, you should keep outside temperature in mind. Even if it’s freezing outside, you’ll still want to provide your grow room with sufficient cooling because the lights are so hot. For this reason it’s important to invest in an air conditioner with low ambient cooling, which can still provide cold air even when it’s below freezing outside.

Calculating the correct amount of BTUs is also critical. Most BTU calculation tools or charts (including our own) don’t account for the added heat of the lights. In general, it is a good idea to add 4,000 BTUs of cooling for every 1000 watts of air cooled lighting and 6,000 BTUs for uncooled lights. These estimates can vary based on your location.

Mini split systems also offer you great flexibility in the temperature that you set in the room. Many units can maintain a temperature of anywhere from 60° F to 90° F all while the outside temperature is anywhere from 14° F to 115° F. This gives you ultimate control over your space.

There are two types of mini split systems ideal for grow spaces: Multi zone systems and commercial grade single zone systems.Mini Split to use in grow room

  • Multi zone mini split systems, like the Daikin RMXS48LVJU Outdoor Compressor Multi-Zone Mini-Split, allow you to cool multiple rooms (or “zones”) separately from one another. This gives you the most control over the temperature in each individual room and may be a great option if you plan on housing multiple grow spaces under your roof. Multi zone systems can also be used in one large space. The indoor units will work together to maintain the overall temperature in the space.
  • Commercial grade single zone systems, like the Daikin FCQ42PAVJU / RZQ42PVJU9 Single Zone System, are ideal for those who plan to have just one grow room. Commercial grade units are ideal for these types of applications where 24/7 operation is required. The higher price will pay for itself over time with unmatched reliability and efficiency.

If you need a cooling system that will perform even when temperatures outside are frigid, we have a couple of different options.

It’s important to have a plan for harsh temperatures if you live in an area where this is a frequent experience. The heat put off by the light bulbs means even when it’s extremely cold outdoors, the indoor temperature still needs regulated.


A proper ventilation system will ensure your grow room exhausts hot air from the space to keep your plants cool. Your best bet is to invest in an industrial-grade exhaust fan such as the following:


Dehumidifier for grow room Since high humidity can make a room feel even hotter than it actually is, it’s important to keep humidity in mind when cooling your grow room. Failure to control humidity can result in mold or rot. Since plants naturally emit moisture, it’s crucial to maintain proper humidity levels in your grow room.

So, what’s the solution for a humid environment? A high-quality, large-space dehumidifier, like the Williams Furnace Company DH90 90 Pint Air Sponge Total Space Dehumidifier. This powerhouse eliminates 90 pints of moisture daily and works for spaces as large as 5000 square feet — perfect for large grow spaces that demand efficient moisture control.

When searching for a dehumidification system, make sure you purchase a large-space or whole-house dehumidifier. Smaller, personal dehumidifiers do not offer nearly as much power and may leave you feeling disappointed.

*Pro-Tip: If you’re interested in monitoring your grow room’s humidity levels, you may want to invest in a hygrometer. This device measures the amount of moisture in the air to help you keep your grow room’s humidity in check.

Water cooling systems

Water cooling is a relatively new technique that works well for many growers. It involves passing chilled water through grow equipment such as lights and dehumidifiers to prevent them from emitting too much heat. In turn, this reduces the reliance on other temperature control methods such as air conditioners.

To set up a water cooling system, you’ll first need to determine which pieces of equipment you wish to cool. Typically, you’ll want to focus on those that emit the most heat (such as lights), but you may decide to water cool most or all of your equipment. You’ll then need to purchase coils to distribute water throughout your equipment or, if you’re water cooling your lights, water cooled light fixtures.

You will also need to purchase an appropriate water chiller to cool the water before it is circulated through your equipment. These, like AC units, are rated by BTU to indicate power: the higher the BTU, the larger its cooling capacity. To determine which size water chiller you’ll need, check out our BTU Calculator tool.

Water cooling systems are not for everyone, especially those who are just starting out or those who live in colder climates. However, for those who live in warmer areas where temperature control is a struggle, water cooled grow rooms can be more efficient than AC. You can purchase water cooling parts and accessories from an online vendor like HTG Supply or Hydro Innovations.

Next Steps

Grow room cooling equipment is a big investment, but a necessary one if you want to yield healthy crops. Total Home Supply stocks a wide assortment of commercial exhaust fans, large-space dehumidifiers and mini split air conditioning systems that work well with grow room operations. Shop with us today and enjoy free shipping to anywhere in the contiguous United States.

Mickey Luongo

Mickey is the resident heating and air conditioning expert with over 15 years of experience in the industry.

One thought on “How to Cool a Grow Room”

  1. Whole House Dehumidifier Pros & Cons - Is it Worth It? says:

    […] you are thinking about getting a whole house dehumidifier, read on to learn more about the benefits before taking the plunge or opting […]

Leave a Reply

Your email address will not be published. Required fields are marked *