How To Cool a Grow Tent & Grow Room?
If there is the one thing just about every indoor cannabis grower struggles with, it’s heat.
During the summer months, the combination of hot weather, growing in a confined space, and heat generated from grow lights and other equipment drives temperatures far beyond what is healthy for marijuana plants.
If you want your plants to make it to harvest, you need to do something about the heat.
Luckily, there’s a lot you can do. Growers have been successfully dealing with heat problems for decades. And so can you.
During the summer months, the combination of hot weather, growing in a confined space, and heat generated from grow lights and other equipment drives temperatures far beyond what is healthy for marijuana plants.
If you want your plants to make it to harvest, you need to do something about the heat.
Luckily, there’s a lot you can do. Growers have been successfully dealing with heat problems for decades. And so can you.
Why Do Grow Tents Heat Up?
Grow tents can heat up due to many reasons. However, the most common reason is that the grow lights are overheating. Lights emit heat – and different kinds of grow lights emit different levels of heat. While LED lights emit the least heat, using an old-fashioned form of lighting such as a High-Pressure Sodium light will produce more heat. These are the biggest reasons as to why your grow tents tend to heat up. There are some grow lights which do not have a proper cooling mechanism and end up accumulating a lot of heat.
If your grow tent does not have a proper ventilation system or a good inline duct fan, there’s a chance that your grow tent will heat up. Other than grow lights, some people also tend to use heaters in their grow rooms which can also impact the temperature of the grow tent. While plants do need a little bit of warmth, excessive heat is never good for them! Let us now take a closer look at why you need to keep the grow tents cool and why is excessive heat bad for your plants:
Grow tents can heat up due to many reasons. However, the most common reason is that the grow lights are overheating. Lights emit heat – and different kinds of grow lights emit different levels of heat. While LED lights emit the least heat, using an old-fashioned form of lighting such as a High-Pressure Sodium light will produce more heat. These are the biggest reasons as to why your grow tents tend to heat up. There are some grow lights which do not have a proper cooling mechanism and end up accumulating a lot of heat.
If your grow tent does not have a proper ventilation system or a good inline duct fan, there’s a chance that your grow tent will heat up. Other than grow lights, some people also tend to use heaters in their grow rooms which can also impact the temperature of the grow tent. While plants do need a little bit of warmth, excessive heat is never good for them! Let us now take a closer look at why you need to keep the grow tents cool and why is excessive heat bad for your plants:
Heating Life Hacks
Sometimes, all we need to do is lower our temperatures only a little bit, so here are my favorite life hacks for lowering temperatures without having to spend any money.
Run your lights at night — This one can also save you money as well, as some power companies have lower nighttime electricity rates. Remember to watch for light leaking into your grow tent as this can cause serious damage to plants in flowering. Most flowering plants need a minimum of 12 hours of uninterrupted darkness.
Change light schedule — Many growers are seeing great results running their plants under 18, 20, and even 24 hours of light a day when in the vegetative growth stage. However, the 16/8 light schedule is a classic for a reason. While running your lights longer may increase yields, you may end up hurting yields if your temperatures get too high from the extra hours of light.
Plan your grows according to season — Most plants can tolerate at least 10-15 degrees more heat when they are in veg compared to when they are flowering, but flowering plants want more light causing a catch-22. If you’re fighting heat in flowering, try germinating in mid-late summer so the plant is flowering in the winter.
Use an oscillating inline fan or clip-on fan — Sometimes all you need to do is get stagnant air moving around in your tent. Most people have a small fan or two lying around in their house. Or, just grab a clip-on fan while you're here. They're cheap and don't take up much space at all, and will help disperse heat.
Changing Where You Grow — Heat rises, and if you live in a two-story home and/or have a basement, then you’ll notice a large difference in temperatures when moving through the house. I can reduce my grow tent’s temperature by over 10 degrees simply by moving it from the upstairs to the basement
Sometimes, all we need to do is lower our temperatures only a little bit, so here are my favorite life hacks for lowering temperatures without having to spend any money.
Run your lights at night — This one can also save you money as well, as some power companies have lower nighttime electricity rates. Remember to watch for light leaking into your grow tent as this can cause serious damage to plants in flowering. Most flowering plants need a minimum of 12 hours of uninterrupted darkness.
Change light schedule — Many growers are seeing great results running their plants under 18, 20, and even 24 hours of light a day when in the vegetative growth stage. However, the 16/8 light schedule is a classic for a reason. While running your lights longer may increase yields, you may end up hurting yields if your temperatures get too high from the extra hours of light.
Plan your grows according to season — Most plants can tolerate at least 10-15 degrees more heat when they are in veg compared to when they are flowering, but flowering plants want more light causing a catch-22. If you’re fighting heat in flowering, try germinating in mid-late summer so the plant is flowering in the winter.
Use an oscillating inline fan or clip-on fan — Sometimes all you need to do is get stagnant air moving around in your tent. Most people have a small fan or two lying around in their house. Or, just grab a clip-on fan while you're here. They're cheap and don't take up much space at all, and will help disperse heat.
Changing Where You Grow — Heat rises, and if you live in a two-story home and/or have a basement, then you’ll notice a large difference in temperatures when moving through the house. I can reduce my grow tent’s temperature by over 10 degrees simply by moving it from the upstairs to the basement
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Why Circulation is Important?
Plants use the stomata, or pores, underneath their leaves to breathe both oxygen and CO2 depending on the day/night cycle. Over time these pores can get clogged by dirt, dust, or other air-borne particles. Usually, rain and wind wash and dry the leaves to keep them clean while moving fresh air around them, but in a greenhouse or grow room you have to replicate the effect using ventilation systems and sprays.
CO2 and Oxygen Replacement
You may be thinking, “Air is everywhere, this room isn’t hot so it’s fine.” But you’d be wrong. Plants are excellent CO2 scrubbers (absorbers that take in CO2 and remove it from the atmosphere). Their leaves greedily take in all of the CO2 around them and begin releasing excess oxygen (during the day). This rapid removal of CO2 is only replenished by moving air. Without circulation of the room’s internal atmosphere, plant growth can become stunted. It’s like trying to breathe after heavy exercise; the plants can’t take in enough CO2 for photosynthesis to occur properly. They can’t create the sugars they need and so development slows or halts. In some extreme cases, larger plants will even lose leaves. Proper air circulation keeps fresh CO2 moving past the leaves of the plants. Remember, you don’t need a strong wind, just a gentle breeze to replenish the air in the room.
Humidity Control
Circulating the air also allows you to control relative humidity. The heat inside a grow room can cause a large amount of moisture as condensation, especially when it’s colder outside, leaving your plants more vulnerable to pests and fungus. Your plants also give off (transpire) a lot of moisture that will build up in a room without air circulation. Replenishing fresher air and cycling out the moist air will prevent this buildup. On the other hand, cycling more humid air into a dry room can keep your plants from drying out in a reverse situation.
Temperature Control
For hot or cold grow rooms, you’ll find that ventilation is the primary method for controlling temperature. Whether you use natural (passive) or mechanical (powered) systems, you’ll gain access to adding or removing heat from your grow room. Extreme temperatures are damaging to plants and can inhibit growth or kill the plants. Every plant is different on what temperature it prefers (varying even by life-stage) so you’ll want to plan accordingly.
Plants use the stomata, or pores, underneath their leaves to breathe both oxygen and CO2 depending on the day/night cycle. Over time these pores can get clogged by dirt, dust, or other air-borne particles. Usually, rain and wind wash and dry the leaves to keep them clean while moving fresh air around them, but in a greenhouse or grow room you have to replicate the effect using ventilation systems and sprays.
CO2 and Oxygen Replacement
You may be thinking, “Air is everywhere, this room isn’t hot so it’s fine.” But you’d be wrong. Plants are excellent CO2 scrubbers (absorbers that take in CO2 and remove it from the atmosphere). Their leaves greedily take in all of the CO2 around them and begin releasing excess oxygen (during the day). This rapid removal of CO2 is only replenished by moving air. Without circulation of the room’s internal atmosphere, plant growth can become stunted. It’s like trying to breathe after heavy exercise; the plants can’t take in enough CO2 for photosynthesis to occur properly. They can’t create the sugars they need and so development slows or halts. In some extreme cases, larger plants will even lose leaves. Proper air circulation keeps fresh CO2 moving past the leaves of the plants. Remember, you don’t need a strong wind, just a gentle breeze to replenish the air in the room.
Humidity Control
Circulating the air also allows you to control relative humidity. The heat inside a grow room can cause a large amount of moisture as condensation, especially when it’s colder outside, leaving your plants more vulnerable to pests and fungus. Your plants also give off (transpire) a lot of moisture that will build up in a room without air circulation. Replenishing fresher air and cycling out the moist air will prevent this buildup. On the other hand, cycling more humid air into a dry room can keep your plants from drying out in a reverse situation.
Temperature Control
For hot or cold grow rooms, you’ll find that ventilation is the primary method for controlling temperature. Whether you use natural (passive) or mechanical (powered) systems, you’ll gain access to adding or removing heat from your grow room. Extreme temperatures are damaging to plants and can inhibit growth or kill the plants. Every plant is different on what temperature it prefers (varying even by life-stage) so you’ll want to plan accordingly.
Final thoughts
Keeping your growing environment cool enough to maximize growth and yields is perhaps the biggest hassle marijuana growers face. Sure, there are plenty of things you can do, but all involve time, effort and money.
You just have to look at it as an essential component to growing indoors. Accept that you are going to have to purchase fans, ducting, filters and perhaps air conditioning units. Ideally, you should also purchase LED grow lights, instead of outdated HPS or MH lights (we still recommend CMH, though we prefer a quality LED).
You just have to look at it as an essential component to growing indoors. Accept that you are going to have to purchase fans, ducting, filters and perhaps air conditioning units. Ideally, you should also purchase LED grow lights, instead of outdated HPS or MH lights (we still recommend CMH, though we prefer a quality LED).
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