Not all climates are conducive to outdoor plant growth, so some people turn to indoor gardening in grow rooms or grow tents.


Not all climates are conducive to outdoor plant growth, so some people turn to indoor gardening in grow rooms or grow tents. These climate-controlled spaces have the ideal conditions for growing plants. And, since you control the heat, humidity and other factors in the space, you have complete control over the types of plants you can grow. You can even have success growing plants that require special conditions not found in your area with a climate-controlled grow room.

If you’re interested in growing a wider variety of plants and produce, learn everything you need to know about grow rooms and controlling their climate below.

Benefits of Using a Grow Room

Benefits of Using a Grow Room

Using a grow room offers several advantages over typical outdoor gardens. Though these types of spaces require an investment in the equipment to sustain the appropriate climate conditions, once set up, you can enjoy gardening inside regardless of outdoor conditions. Other benefits of using a grow room include:

  • Avoid using pesticides: Grow rooms can reduce the need for pesticides in the garden. Because the room is isolated from outdoor bugs and other pests, the plants grown there won’t face as many problems of bugs eating them or compromising their growth.
  • Gain total climate control: Rather than worrying about heatwaves or droughts, gardeners who use grow rooms take charge of the moisture levels, lighting and temperature in the growing area.
  • Grow unique plants: Grow rooms allow for the production of plants that otherwise would not flourish in your region’s growing zone. The United States has a variety of growing zones based on precipitation and temperatures. Plants recommended for growing in each zone have moisture and heat requirements close to those of the zone’s natural climate. For those in areas with short growing seasons, cold weather or low levels of light, a grow room allows for gardening that the climate does not permit.
  • Take advantage of indoor space: Those who don’t have large yards or greenhouses for growing plants outside can still enjoy gardening with a grow room. By growing plants inside, anyone can make more use of the space they have and raise a variety of produce or other plants.

What Is a Grow Room Climate?

The grow room climate covers everything from the temperature, soil, moisture levels and lighting. The climate inside a grow room must match the outdoor conditions plants would normally experience to ensure optimum production.

The specifics for the grow room climate depend on the needs of the individual plants. Plants with vastly differing needs will need separate grow rooms or grow tents to thrive in the correct environment. Always use the ideal growing conditions for your chosen plants when setting up the grow room climate. For instance, you may need different conditions for hydroponically grown lettuce and chili peppers grown in soil.



The temperature should closely match the climate and season of the plants you grow inside. Many plants will thrive in warmer conditions, for instance.

A grow room’s temperature can include both the growth medium and the air temperature. Monitoring and controlling both could determine the success of the plants grown inside the space.

Consider a study of hydroponically grown butterhead lettuce. The lettuce grew three times faster when grown in solution at temperatures ranging from 65 to 70 degrees Fahrenheit compared to a temperature range of 10 degrees Fahrenheit lower. The slightly warmer temperatures were surprising, considering that lettuce typically grows in cooler temperatures outside. But soil temperature or hydroponic solution temperature also played a role in the lettuce’s growth.

Heating a grow room to this temperature range may not be cost-effective depending on the time of year and the temperature of the rest of the building. When heating a grow room to 70 degrees Fahrenheit during light hours is too expensive, an alternative to helping improve growth is slightly increasing the temperature of the hydroponic nutrient solution. The same study found the biggest growth in the lettuce when using a hydroponic solution warmed to 71.4 degrees Fahrenheit when the air temperature ranged from 55 to 60 degrees Fahrenheit.

Soil or Growth Medium

Soil or Growth Medium

Whether to use soil or a hydroponic medium is another aspect of controlling the grow room climate. Using soil requires regularly monitoring the levels of nutrients and feeding the soil to ensure the plants’ growth. Occasionally, the soil may harbor pests that require you to remove or protect the plants.

It’s worth noting that choosing hydroponics is not always an easier solution. While hydroponically growing in a grow room allows for pesticide-free gardening and better control over the conditions the plant grows in, you need to carefully choose the nutrient solution for your plant. Several factors, including pH and dissolved salts in the solution, can impact the solution’s effectiveness in providing the plants with the food they need to grow best.

Other aspects of the growth medium are also essential to control in a grow room. As noted, the temperature of the hydroponic nutrients or soil can make a difference in the growth rate of butterhead lettuce and other plants.

You should also decide if you want organic or conventional fertilizers for adding nitrogen and other nutrients to the soil or hydroponically grown plants. For leafy greens, a study showed that conventional fertilizers produced larger vegetables with less maintenance for the system. Conventional fertilizers are also easier to use and a better option for beginners. But organic fertilizers are available for those who prefer to grow plants without synthetic pesticides or fertilizers.

Moisture Levels

Moisture Levels

Moisture levels that you control in a grow room include both the humidity and water given to the plants. Controlling humidity to keep it from getting too high is essential for protecting plants from physiological damage or mold growth. For example, lettuce and other leafy greens may experience tip burn when the humidity is too high and the plants cannot take enough calcium from the soil. Regulating the humidity levels inside the grow room helps prevent this condition and others spurred by high moisture levels in the air.

Controlling humidity can be challenging depending on the heat and watering method used. Excessive watering leads to higher humidity in the air because the extra water evaporates. But underwatering can cause plants to wither.

The temperature also plays a role in the amount of moisture in the air. When the temperature in a grow room increases by 20 degrees Fahrenheit, the moisture capacity of the air doubles. That relationship means an air temperature of 80 degrees Fahrenheit holds double the moisture of air that is 60 degrees Fahrenheit.


Outside, plants have daily cycles of several hours of light and darkness. Some plants require a minimum number of hours of shade or darkness to grow properly and produce. But other plants don’t have this requirement.

Pepper plants, for example, do not need any time in the dark to produce flowers and fruit. But tomatoes need at least six hours of darkness a day to bloom and produce fruit. Understanding light-dark ratio requirements is part of maintaining an adequately controlled grow room. The quality of the light is just as essential as the number of hours the plants get, as well.

Plants need light to grow properly, but standard indoor lightbulbs often don’t suffice for grow rooms. Plants have differing needs for the light they are exposed to each day. Some plants need partial shade when grown outside, while others must have full sun. When growing indoor plants, all the light comes from the grow lights you use. Therefore, you need to know one of several light measurements to control it.

One such metric is daily light integral (DLI) in moles per photon per square meter per day. The DLI plants need will vary with how much light they should get. Purdue Extension has a listing of the specific DLIs for individual plants. You can also consider these ranges based on how much light your plants need:

  • Low: For low-light or shade plants, this should range from 5 to 10 moles.
  • Medium: Plants that need partial sunlight levels or medium light should have DLI from 10 to 20 moles.
  • High: Plants that need high levels of light have DLIs ranging from 20 to 30,
  • Very high: Ones that need full sun or very high light levels need 30 to 50 moles of DLI.

Other metrics to determine the photosynthetically active radiation (PAR) reaching plants are photosynthetic photon flux (PPF) and photosynthetic photon flux density (PPFD). These related measurements indicate how much light the source produces each second and how much light reaches a square meter of the plant each second, respectively. PPF and PPFD use the measurement unit of micromoles per square meter per second. For the best plant growth, choose lights that offer 400 to 800 micromoles per square meter per second.

Grow lights are designed to provide specific wavelengths of light to optimize plant growth. The light wavelength, also known as light quality for grow lights, is critical for optimizing indoor plant growth. By choosing light sources that offer specific wavelengths, you can increase food production in the plants, improve overall growth or encourage flowering.

Generally, most plants grow best with light wavelengths between 400 and 700 nanometers (nm). Within this spectrum, you’ll find:

  • Blue light: A wavelength of 440 nm encourages plants to produce more chlorophyll, their source of food, improving overall plant health.
  • Red light: With a wavelength of 660 nm, red light helps plants to grow bigger and flower.
  • Far-red light: At 730 nm, far-red light also helps plants flower and grow larger.

These wavelengths are especially helpful when growing plants with long daylight requirements.

Because distance also affects the intensity of the light reaching the plants, you may need to experiment with the placement of the grow lights to optimize plant growth. Start with your light source 12-18 inches from the plants or refer to the manufacturer’s recommendations. If the plants start to wither or burn, place the grow light farther from the plants. If the plants stretch toward the light, leave the light on longer or move it closer.

Why Is Grow Room Climate Important?

The climate inside a grow room is just as crucial for the plants’ growth as the conditions they would experience if grown in a field. A proper balance of temperature, humidity, lighting, and nutrients can ensure the plants have everything they need to grow their best.

Mismanaged grow rooms may produce plants that are too small, flower too soon or experience mold or mildew. Because plants have different growing needs, you cannot use the same parameters for all your indoor crops. Understand the needs of your plants, just as gardeners who grow outside do, to get the best results.

What Impacts the Grow Room Climate?

What Impacts the Grow Room Climate?

Several factors will affect the grow room requirements and climate that results during growth. When controlling a grow room’s temperature and humidity, consider the following as possible reasons the measured values may not match what you expect.


How large or small is the grow room? Smaller spaces will heat and cool faster than larger spaces, while smaller spaces may also have humidity build faster than larger, more open spaces.

See if the space in the room has openings to the outside. Fresh air access may influence temperatures inside the room, especially if the outside air is significantly different from that inside the grow room. Colder temperatures outside the grow room could send a chilly draft into the growing space. Cooler temperatures outside the grow room may also draw heat out of the growing area, raising heating costs for the plants.

Type and Number of Plants

The types of plants you grow will affect the conditions you need to have for the grow room’s climate. If you will have multiple plant types in the space, use those with similar temperature and humidity needs. Be sure to space out the plants enough to prevent temperature increases and ensure adequate ventilation around each plant. Too many overcrowded plants will cause the grow room’s temperature to increase.


Ventilation will affect the humidity and temperature levels inside the grow room. If you have too much humidity, vent the room to remove the excessively moist air. For spaces that are too hot and humid, air conditioners can reduce temperatures and humidity levels. Good ventilation can prevent mold or mildew from growing on plants, too.

Type of Light Bulbs

If you’ve controlled everything else but the temperature in the grow room is too high, look at the lights you use. Incandescent lights can increase the temperature inside a grow room by generating heat. Choose LED lights for lower energy requirements and less heat production.

Equipment to Control Grow Room Climate

You will need equipment to set up and maintain the grow room’s climate. You’ll also need equipment and supplies to feed and help your plants grow after creating your grow room. The most commonly needed equipment for regulating a grow room climate includes lights, water delivery systems, ventilation and monitoring devices.

Light Fixtures and Bulbs

Light Fixtures and Bulbs

The type of light fixtures and bulbs you use is key. You will want to choose grow lights that offer enough light in the right spectrum for your plants to thrive. You should also have enough lamps to allow for their light arcs to overlap each other and avoid having any plants in the shadows.

While LED lights are a popular option for their energy efficiency and availability in blue, red, far-red or full-spectrum wavelengths, there are other types of lights, including:

  • High-intensity discharge (HID) lights: HID lights are brighter and put out more light than LED lights. Commercial growers prefer these, despite the availability of only one spectrum of light with HID lamps.
  • High-pressure sodium (HPS): A specific variety of HID lamps are HPS. These bulbs produce a light that is closer to sunlight and has more brightness compared to MH lamps. The higher levels of light from HPS lamps produce greater flowering results.
  • Metal halide (MH) lamps: MH lights provide a balanced spectrum of light that is better for use with leafy greens like lettuce or kale.

Whichever type of light you choose, you must have a base to accommodate the light. HID ballasts and fixtures may allow for changing between MH conversion, HPS and HID bulbs. But if you’re using standard MH lights, you need MH ballasts to operate them. If you choose LED lamps, you only need a nearby standard light socket instead of special ballasts or fixtures to operate them.

Water Delivery System

Water Delivery System

Watering grow room plants, especially hydroponically grown ones, requires equipment to treat the water and deliver it. Giving plants too much water in soil or not enough oxygenation in hydroponics can stunt growth. Misting them too often, especially after flowering, can lead to fungal infections. Use a water delivery system to take the effort and thought out of delivering the proper amounts of water to both soilless and soil-based indoor gardens.

The type of water delivery system should meet the plants’ needs. Plants that grow in soil or soilless mediums need watering only when the top is dry. Hydroponically grown plants using a nutrient film technique (NFT) or deep water culture (DWC) must always have water to cover the plants’ roots. Hydroponic gardens require equipment to oxygenate the water before delivering it to the plants. Oxygenation prevents rot from killing the plant’s roots, which would also happen if you overwatered plants in soil with untreated water.

As noted, the temperature of the water used for hydroponics can also influence the growth of the plants. Some grow rooms may benefit from water chillers or heaters as part of the water treatment system.

Options for water treatment and delivery include:

  • Aeration pumps to oxygenate the water
  • Water filters or reverse osmosis water purifiers to remove unwanted minerals and contaminants from water
  • Filter replacements
  • Water testing kits to monitor pH and make necessary adjustments
  • Heaters and chillers

Not every grow room will require all the above water treatment options. But for hydroponic gardening that relies on the quality and oxygenation of water feeding the roots, such water treatment could be the factor that determines plants’ successes or failures.



Ventilation is vital for keeping the humidity and temperature under control. An air conditioner could provide the needed ventilation while reducing high humidity and temperatures. This addition may not be a good choice if the grow room needs warming to an optimal temperature. Heaters can warm the space, but you will still need fans to keep the air moving around the room to control humidity. Ventilation also brings fresh air in with carbon dioxide (CO2) to help the plants with photosynthesis.

Some growers also add CO2 to the atmosphere in the grow room. Because plants use CO2 to make food, adding more of this gas to the air improves food production and growth. The ideal range for CO2 in a grow room is between 1,500 and 2,000 parts per million (PPM).

Use a digital controller with a regulator and CO2 tank to facilitate the process of adding carbon dioxide to the grow room to attain the perfect levels. You can find these as complete kits or choose other CO2 supplement products to create your own method of raising this gas level in the grow room.

Monitoring Equipment for Temperature and Humidity

Monitoring Equipment for Temperature and Humidity

The only way to know how well your grow room’s climate matches the ideal conditions is through monitoring equipment. You should use thermometers to find the temperature of the air and soil and take measurements of the room’s humidity. You can usually find thermometers that indicate both the air temperature and relative humidity. A probe thermometer will tell you the soil temperature.

If you supplement the room with CO2, you will need a device to measure the amount of that gas. And remember to monitor the light your plants get, as well. Light meters are readily found as apps for smartphones or from nurseries or other suppliers if you want to know the exact amount of light your plants receive from your setup.

Depending on the monitoring equipment you get, you can connect monitoring equipment to controllers for temperature and humidity to effortlessly maintain the climate inside the grow room. Though technically not a monitor, timers are another useful tool, especially if you grow plants with required amounts of light and dark. Use the timer to turn off the grow lights after a set number of hours and turn them back on after the dark cycle ends.

How to Control Climate in a Grow Room

To control the climate in a grow room, you must use the data collected from air and soil temperature monitoring devices and humidity measurements. This information will tell you if the climate is too hot, too cold, too dry or too moist. You can then make adjustments to the temperature and humidity by adjusting the ventilation, cooling and heating of the room.

How to Control Temperature in a Grow Room

Controlling temperature in a grow room may require you to bring in an air conditioner, fan or heater. Adequate ventilation will help keep the temperature in your grow room close to appropriate levels. If you use a heater or air conditioner, connect its controller to a thermostat that you can set to the optimum temperature for your plants. Try to maintain temperatures within a range of 60 to 90 degrees Fahrenheit.

You may have different temperature settings for light and dark cycles. If you have dark cycles, drop the temperature by five degrees Fahrenheit.

How to Control Humidity in a Grow Room

How to Control Humidity in a Grow Room

The humidity in a grow room also needs regulating. Use a meter to find the relative humidity for the room. If the grow room is too moist but not hot enough to use an air conditioner in, use a dehumidifier. Unlike air conditioners that cool and remove humidity, dehumidifiers only take excess moisture from the air without affecting the temperature. Good ventilation can also push moist air out and bring in fresh, drier air to the grow room.

If the space is too dry, you may need to integrate a humidifier into the room. The dryness of a grow room may depend on whether it is connected to the rest of the building’s climate control system. Often, homes are comfortable around 50% humidity or lower. In some areas, the internal humidity in a home can be much lower. For plants with higher humidity needs, a humidifier could solve the problem.

What You Need to Set up a Climate-Controlled Grow Room

What You Need to Set up a Climate-Controlled Grow Room

To set up a successfully climate-controlled grow room that will produce the best results, you need several things. Before you start your grow room, make sure to check off the following requirements for the process of growing plants inside:

1. Knowledge

There are hundreds of plants you could grow inside in a grow room. Take some time to research the temperature, humidity, lighting and nutrient needs of the specific plants you want to grow.

You can readily find these requirements for various plants online through university extensions or from local nurseries. Even the sources where you purchase seeds or plants can help you find out more about the plant’s specific requirements for growth. Local libraries also have books on gardening and growing requirements for specific plants.

There is no shortage of information on plant requirements. But you must take the first step of researching what your grow room plants will need before choosing equipment and supplies for them.

2. Plants

Next, you need to get your plants. Do you want to start your plants from seeds or seedlings? Find a reputable nursery for your plant source to ensure the health and vitality of the plants. Local nurseries are better if you want to grow plants from seedlings. But you can get seeds online for hard-to-find plants or for those that don’t typically grow in your local climate.

3. Equipment

The equipment is the second-most critical component of your grow room after the plants. You will need lights, temperature and humidity monitors, ventilation methods, growing medium and nutrients for your grow room. If you don’t have a separate room, you will also need a grow tent for your indoor cultivation.

Don’t forget to match the capabilities of your grow room equipment to what your plants will need. If you will grow plants that require intense, full sunlight, you need grow lights that can provide that type of lighting.

You must also choose whether you want to use conventional soil-based gardening techniques or soilless hydroponics. The equipment you purchase to sustain the plants should support the needs of your gardening method, too. For instance, you will need specialized containers and water delivery systems for hydroponic gardening inside a grow room.

4. Patience and Assistance

Have patience with your indoor grow room gardening. Even knowing specific plant needs, you may still need to make minor adjustments to optimize plant growth. Let your first crop be an experiment to fine-tune your grow room and growing methods. By the time you grow your second crop, you will know more about controlling the climate of your grow room to get the best production from your plants.

Also, don’t be afraid to ask for help. Getting assistance from experts online, in nurseries or from equipment suppliers can help you to get accurate information about your growing concerns. Asking questions as they come up can prevent you from making mistakes that could cost you the health of your plants.
Grow Room FAQs

Even with the right equipment, adjusting the climate in a grow room may come with some considerations and questions. Find your answers with some of the most frequently asked questions about indoor grow rooms or indoor gardening:

What Temperature Should I Keep My Grow Room At

1. What Temperature Should I Keep My Grow Room At?

The specific temperature for your grow room depends on what you want to grow. For instance, after germination, seedlings in commercial spaces grow at temperatures of 75 degrees Fahrenheit during the day and 65 degrees Fahrenheit at night or during night cycles of lighting. After the seedlings grow larger, this temperature range may not be required, but temperatures should still be comfortable for you. Know your plants’ temperature requirements, but, when in doubt, choose temperatures comfortable for you, around 70 degrees Fahrenheit during daylight cycles.

2. Do I Need Heat for a Grow Room?

Whether you need heat for a grow room depends on the unheated conditions. If the grow room maintains the ideal temperature without supplemental heat, you may not need to heat the space. During winter, you might want to bring in a space heater to maintain the optimum temperature for growth, especially if you live in a cold climate. Use a thermometer to monitor the air temperature inside the grow room to decide whether you need to heat the space.

3. How Hot Is Too Hot in a Grow Room?

Ideally, you want to keep a grow room below 80 degrees Fahrenheit, especially for growing cooler weather plants such as leafy greens like spinach and lettuce. More heat tolerant plants may sustain temperatures of 85 degrees Fahrenheit before experiencing damage.

4. What Happens if a Grow Room Is Too Hot?

Excessive heat in a grow room can cause several problems with plants, depending on what you grow. For instance, lettuce and spinach will bolt if the temperatures are above 80 degrees Fahrenheit. Bolting happens when plants produce flowers too early, making the leaves unpalatable.

Another issue caused by excessive heat is too much humidity in the air. Hotter air holds more moisture. Too much moisture in the air or condensation on plants can lead to powdery mildew or fungal growth.

When the humidity remains low but the temperature is too high, the plants may drop their blooms or slow their growth, resulting in smaller plants. Watering requirements increase because the plants may use up to 90% of their water to keep themselves cool when in hot, dry conditions. Lowering the temperature and ensuring the plants get enough water can help plants experiencing heat stress from a grow room that is too hot.

5. How Do You Climate Control a Grow Tent?

To climate control a grow tent, follow the same procedures you would use for a grow room. Monitor the heat and humidity in the space, use LED grow lights, don’t overcrowd the plants and vent the space with a fan to regulate humidity and temperature.

Find the Right Equipment for Maintaining Ideal Grow Room Conditions at HTG Supply

Find the Right Equipment for Maintaining Ideal Grow Room Conditions at HTG Supply

Whatever plants you want to grow inside, you need the right equipment to create the ideal environment, and HTG Supply can help. From grow lights and grow tents to monitoring tools and other accessories, we have what you need to make a successful grow room. With nationwide locations, fast shipping and a selection unmatched by our competitors, HTG Supply will have what you need for optimizing your indoor grow tent or room. Shop our selection of grow room essentials here at HTG Supply.

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