How to Cool a Grow Room

Grow rooms are great for avid gardeners who want to exercise their green thumb year-round. However, they need to be properly planned out and maintained if the plants are to flourish. One such issue faced by indoor growers is proper 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 just survive but thrive, we came up with this guide for grow room HVAC and ventilation.

Why Grow Room Cooling is Essential

Plant Health: Excessive heat can stress plants, leading to poor growth, lower yields, and even death in extreme cases.

Optimal Growth: Different plants have specific temperature requirements for ideal growth. Keeping the temperature in the right range ensures plants thrive.

Humidity Control: Cooling systems also help manage humidity levels, which can prevent mold and mildew from infesting plants.

Energy Efficiency: Efficient cooling reduces energy costs and makes your grow operation more sustainable.

The Different Types of Grow Room Cooling Systems

1. Air conditioners

Air conditioners can be an excellent choice for cooling grow rooms; you just need to buy the right one. Here are the different types of AC systems suitable for grow rooms.

Portable Air Conditioners

These are flexible and easy to install, making them ideal for smaller grow rooms or temporary setups. Look for units with programmable thermostats and timers to maintain consistent temperatures.

Our Recommended Portable AC for Grow Rooms:

Friedrich ZCP12DB 11000 BTU Class ZoneAire Dual Hose Portable Air Conditioner with Built-In WiFi – R32 Refrigerant

This 3-in-1 portable AC provides air conditioning plus dehumidification and fan with 11,000 BTUs of cooling capacity. It can cool grow rooms up to 400 sq. ft. while removing up to 3.5 pints of moisture per hour.

This portable AC unit includes built-in WiFi for on the go control through the FriedrichGo app. It also works with Amazon Alexis and Google Home. It uses a self-evaporative condensate system so there is no bucket to empty, plus it has condensate overflow protection which will shut the unit off to prevent overflow if the tank becomes full. Its dual hose exhaust snaps in and can be extended from 24″ up to 60″.

Window AC

Effective for small to medium grow rooms, window units are more energy-efficient than portable models. Ensure the unit has sufficient cooling capacity for the size of your grow room.

Our Recommended Window AC for Grow Rooms:

Friedrich CCV24A30A 24000 BTU Chill Premier Inverter Smart Window Air Conditioner – 230V – Energy Star – R32 Refrigerant

The new Chill Premier Inverter Series is Friedrich’s Premium Line of “smart” room air conditioners now with variable comfort / inverter technology. The Premier Inverter units allow for the compressor to operate at the capacity needed at any given time.

This EnergyStar Rated model unit features 24,000 BTUs of cooling and boasts  a CEER rating of 12.7. It uses the newer, efficient R-32 refrigerant. R32 is up to 12% more efficient than R410A, resulting in lower Global Warming Potential (GWP). The lower the GWP, the better for the environment.

The Chill Premier Series also includes a window installation kit with solid side flaps (vs accordion-style). Designed with the homeowner in mind, the SimpleSill Design allows the window to be opened and closed after the unit is installed! The three-step installation kit includes a one-piece frame, included hardware and expandable side panels to lock the unit in place.

Ductless Mini-Splits

These systems are pricier but offer better long-term performance and energy efficiency. Mini-splits offer precise temperature control and are highly efficient. They are perfect for larger grow rooms where maintaining consistent conditions is crucial. In addition, they allow you to maintain a set temperature for your grow room that’s separate from the rest of your home.

Our Recommended Mini Splits for Grow Rooms:

There are two types of mini split systems ideal for grow spaces: Multi zone systems and commercial grade single zone systems.

• 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.

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

• The Daikin 2F018535-2 Ultra Low Ambient Kit is available for use specifically with the Daikin FTX36NVJU / RK36NMVJU 36000 BTU Cooling Only 17.9 SEER Sky Air Mini Split system. This ultra low ambient kit allows you to cool your grow room even when outdoor temperatures reach -40°F.

• Likewise, we have the Daikin 2F018535-1 Ultra Low Ambient Kit made specifically for the Daikin FTX30NVJU / RK30NMVJU 30000 BTU Class Cooling Only Sky Air Single Zone System. This kit and mini split combination will also allow you to continue cooling a room even when the temperature outside has reached a bitter -40°F.

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 to be regulated.

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2. Ventilation Systems

Inline Fans and Ducting

Inline fans are used to expel hot air from the grow room. Paired with ducting, these fans can be used to exhaust heat from grow lights and other equipment. Ensure your fan has the right CFM (Cubic Feet per Minute) rating for your grow room size.

Oscillating Fans

These help circulate air within the grow room, preventing hot spots and promoting uniform temperature distribution. While they don’t directly cool the room, they enhance the effectiveness of other cooling systems.

Our Recommended Grown Room Ventilation Fans

• The S&P CWD10PH1AS Direct Drive Centrifugal Sidewall Exhauster is a low-profile yet powerful 10” wheel exhaust fan that expels clean air from industrial facilities. It does not require any ductwork to install and mounts on the wall.

• The S&P CWD14QM1AS Direct Drive Centrifugal Sidewall Exhauster is similar to the CWD10PH1AS except it measures 14”, making it ideal for those seeking even more power.

• The S&P SDB16MH1S Downblast Belt Drive Centrifugal Roof Exhauster installs on the roof for more efficient ventilation. Its belt driven design offers quiet operation and low RPMs.

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3. Chillers

Water Chillers

Used primarily in hydroponic systems, water chillers cool the nutrient solution, which indirectly lowers the ambient temperature in the grow room. They are especially useful in larger setups where controlling the temperature of the nutrient solution is crucial.

Air Cooled Chillers

These units cool the air in the grow room by removing heat from the water or glycol solution. They are ideal for large commercial operations but are more complex and expensive to install.

Evaporative Coolers / Swamp Coolers

Evaporative coolers work by passing air over water-saturated pads, cooling the air through evaporation. They are most effective in dry climates where humidity is low.

These coolers are energy-efficient and add humidity to the air, which can be beneficial in dry environments. However, they are less effective in humid climates and may require additional dehumidification.

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4. Dehumidifiers

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.

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.

Recommended Dehumidifier for Grow Rooms:

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.

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5. 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.

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Key Factors to Consider for your Grow Room Cooling System

1. Grow Room Size and Layout

The size and shape of your grow room determine the type and capacity of the cooling system you need. Measure the dimensions and calculate the total volume of the space to determine the required BTUs or CFM.

2. Heat Load

Consider all sources of heat in your grow room, including grow lights, equipment, and even the ambient temperature of the surrounding environment. This will help you choose a cooling system with the appropriate capacity.

Most BTU calculators (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.

3. Humidity Control

Cooling systems can affect humidity levels, which need to be carefully managed to prevent issues like mold, mildew, and plant rot. Choose a system that either helps maintain the desired humidity level or can be paired with a dehumidifier.

4. Energy Efficiency

For AC units, look for systems with high SEER (Seasonal Energy Efficiency Ratio) ratings, which indicate better energy efficiency. In the long run, energy-efficient systems will save you money on operating costs.

5. Noise Level

Cooling systems can be noisy, which might be disruptive depending on the location of your grow room. Look for systems with lower decibel ratings or consider installing noise-reducing insulation.

In general, mini splits and properly sealed water cooling systems emit the least amount of noise.

6. Installation and Maintenance

Consider the complexity of installation and ongoing maintenance. Some systems, like mini-splits, require professional installation, while others, like portable ACs, are plug-and-play. Regular maintenance, such as cleaning filters and checking refrigerant levels, is essential to keep the cooling system running efficiently.

7. Low Ambient Cooling

When deciding how to cool your grow room, 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 a cooling system or AC with low ambient cooling performance. This means it can still provide cold air even when it’s below freezing outside.

Mini splits excel in this regard. They 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. 

Tips to Optimize Grow Room HVAC and Cooling

☑ Insulate Your Grow Room

Proper insulation prevents heat from entering the grow room and helps maintain consistent temperatures. Use reflective materials to minimize heat gain from external sources.

☑ Optimize Airflow

Efficient grow room ventilation plays a key role in cooling. Ensure that air circulates effectively throughout the grow room. Position fans to avoid dead spots and ensure hot air is exhausted efficiently.

☑ Use Light Timers

Run your grow lights during cooler parts of the day, such as at night, to reduce the cooling load on your system. This can greatly reduce utility costs while prolonging the life of your cooling equipment.

☑ Monitor and Control

Use thermostats, hygrometers, and automated controllers to monitor and adjust temperature and humidity levels. Smart controllers can optimize the operation of your cooling system based on real-time data. You can even set routines, schedules or IFTTT functions to automate the system for optimized growth without constant intervention.

☑ Dehumidify if Necessary

If your cooling system increases humidity, use a dehumidifier to maintain optimal levels. This is especially important in areas where humidity is naturally high.

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.