Weather you look at our T5 fixture reviews or growers guide articles we often talk about the heat that T5 grow lights emit. And although it is true that T5 lamps don’t emit a lot of heat therefore usually don’t cause a lot of heat related problems, there still are cases, when you need to think about installing some kind of additional ventilation or cooling system in your grow room to keep your plants feeling good enough to grow. So I thought it is time to tell you more about how to efficiently cool down your grow room so your plants don’t suffer any heat related damage.
Not all grow rooms need to be cooled down, because many times your grow room will be big enough to handle this process itself and to keep plants nice and fresh. But for example if you have a very small grow space or if you are growing plants indoors in the hot summer months, then you will probably will have to think of ways how you can discharge the excess heat from your grow room, to let the cool air circulate in it and give your plants the cool environment they need.
One of the best ways to achieve great and efficient grow room cooling is to install additional ventilation in your grow room. Ventilation means that the air in your grow room will circulate better, moving the hot air out of your grow room and the cool air into it. And to attain this goal most likely you will need to install a fan as well as ventilation ducts that will discharge the hot air from your grow room and will bring the cool air into the grow space.
The placement of the fan isn’t that important, because most of the time plant growers install their fans where it is convenient to them and where it the fan doesn’t interfere with the plant growth. 
But for the ventilation ducts are a bit different, because with them you need to think about where the hot air will go and the cool air will come from. Which is why the duct that will discharge the hot air should be placed close to the ceiling of your room, but the one, that will supply the cool air to your grow room, on the ground level of the room where your indoors garden is located, because this way you can be sure that your plants receive the coolest possible air (as hot air rises and cold air stays at the bottom of a room) and that the hot air isn’t going straight back into the grow room which would eliminate the whole purpose of you having a ventilation system.
But how to know how big of a fan you need for your grow room? That can be easily determined by doing some quick calculations. Just multiply the width of your grow room with the length and height of it in inches (or cm depending on what unit system you use) and divide this number with 5. That will show you how much air needs to be moved by the fan each minute for it to be able to completely replace the hot air in your grow room with the cold air in five minutes. This number will be in cubic feet (or cubic centimeters if you use the metric system) and you should buy a fan that has this number or one close to it on the packaging.
But if your heat problem isn’t as serious and you don’t want or don’t need to invest in setting up a full on ventilation system then there are things that you can do to help your plants keep cool. One of the things I would recommend you to do especially during the summer is to run your lights during the night, because at night the temperatures outside (and therefore in your house) naturally drop so you won’t have to worry about the heat from the sun, only about the heat that is generated by your grow lights. And the second thing you can do is to install temperature controllers (preferably with fans) in your grow space because this will make sure that once your grow room gets too hot your grow lights will automatically turn off (or if you have fans linked to these controllers then they will automatically turn on) this way keeping your plants from overheating and keeping your grow room at a reasonable temperature.
