Exhaust Fan Calculator
for Indoor Grow Rooms

When controlling temperatures manually, digital timers can be set to control the exhaust fans and CO2  (particularly during 'lights out')

Use the exhaust fan calculator below to figure out the appropriate type and size exhaust fan for you. The first thing to consider is the size of the garden space you are planning to grow in. The general rule is to have an exhaust fan that will completely exhaust the garden area in 5 minutes or less. This is how...

Exhaust Fan Calculator:

First, figure out the cubic feet of your garden area. Measure the floor of the area (example 3 feet by 4 feet), and multiply this by how tall the area is (example 8 feet). In this example, you would have 3 times 4 times 8, which equals 96 cubic feet.

Naturally, if you buy a 96 cubic foot per minute (CFM) fan, you would be able to exhaust the whole room in one minute.

If you divide this number by 5, you get the smallest CFM (cubic foot per minute) that you would want to go with. In this example, 96 divided by 5 = 18.24 CFM. An 18.24 cubic foot per minute fan is the smallest fan you would want to consider.


Now, to get a better idea of your fan needs, you need to look at your whole exhaust setup. Your light, your fan, and the way you move the air through the garden area are known together as your exhaust setup.


Other Things to Consider

In reality, there are a number of things to consider that will affect the actual cubic feet that your garden exhaust fan will move each minute. These things fall into three categories...

  • your air exhaust duct runs

  • your light reflector options

  • the addition of a carbon filter


Placing the Carbon filter high allows you to exhaust the hottest air from the room first

The exhaust fan is designed to move air FROM your garden area TO another area. In order to do that, you normally need to move the air through air ducts.


6 inch ducting is absolutely the minimum size to consider using, in my opinion

The minute you connect an air duct to your exhaust fan, the amount of air you can move (your CFM) drops. This is because it takes more energy to blow air through ten feet of air ducting compared to just blowing air straight out of the fan. The longer the air duct run the more your CFM will drop, especially if there are bends and turns. Try to keep it under 20 feet.

Your grow light reflector can block your airflow and reduce your CFM. This is critical information for anyone who wants to get started in the right direction. These detailed considerations can be found in my about your reflector section. I highly recommend you read this section.

The above are all good reasons to get an over-sized fan (one larger than indicated by the exhaust fan calculator).

This 273 CFM squirrel cage fan costs about the same as some much stronger centrifugal fans

As I discussed in the garden exhaust fans page, there are only two types of fan that are appropriate to use as exhaust fans... they are squirrel cage fans (pictured here) and centrifugal fans. Everything you have read up to this point can be accomplished with a squirrel cage fan.


Exhaust Fan Options
When Using a Carbon Filter

Centrifugal fans are the most efficient air movers. Recently, they have also become more affordable than squirrel cage fans. Pictured here is a 465 CFM fan

If you decide to add a carbon filter, than a squirrel cage fan is not quite powerful enough to do the job well. You need the kind of air pressure only one kind of fan can deliver. You need a centrifugal fan (pictured here). Your centrifugal fan will both filter your air, cool you lights, AND exhaust your garden area.

The Carbon filter here is the highest rated on Amazon. Carbon filters are the most effective way to control unwanted odors

In addition, a centrifugal fan will maintain it's CFM in many situations where a squirrel cage fan will not, so it is not necessary to get an "over-sized" fan. Simply follow whatever CFM recommendation the exhaust fan calculator indicates.


The Exhaust Fan Setup

By now you have a good idea of where your garden will be, what size it will be, what light you will use, and what fan to use. Now it's time to put it all together. It is critical to control the high temperatures in your grow room....that means you must spend a little time and money running your exhaust setup properly.

Leave the exhaust fan calculator page and
Visit the Exhaust Setup Page


Check out Grow Light options for your garden


Check out Hydroponic Systems for your garden


All of the items that I personally use and recommend!

AffordableGarden Design&Setup

(10 week update below)


Find out the cheapest and easiest ways to garden productively in this article.

Hi everyone, Jason from Jason's Indoor Guide here. When I got started with hydroponic gardening more than 24 years ago, my first garden used rockwool cubes and B.C. Nutrients....and I remember thinking to myself yeah, sure, there may be a lot of advantages to gardening with hydroponics, for example there are very few pest problems, therefore very little pest control, no weeding, no plowing or tilling the soil, no soil testing or having to add things into the garden soil, no watering the garden....but for someone who just wants to grow their own vegetables and have more control over their food supply and the quality of the food that they eat, the cost of constantly having to buy grow media and hydroponic nutrients makes this an expensive hobby for most people...


Epic Nutrient Change



I suppose when you take into consideration how much money you save NOT having to buy food at the grocery store, it is surely cheaper to grow your own food hydroponically even with the cost of high quality nutrients. Nevertheless, I didn't have a whole lot of money to work with and I needed to make my efforts as affordable and effective as possible....and in the last 24 years I HAVE learned a thing or two!

As you browse through Jason's Indoor Guide, you will notice all of the systems that I use personally are homemade systems. As I got 3 or 4 years of experience under my belt, I quickly adopted a preference to standing water systems and systems that use expanded clay pellets or lava rock, because the media is re-usable and it eliminates a huge operating expense. So once a hydroponic system is built, garden maintenance is minimal- check and adjust the nutrient solution daily, and to change it completely every 2 weeks....and the biggest operating cost is the hydroponic nutrients. (and the electric bill, lol)...


Homemade Cloner



And, regarding the cost of the nutrients....I experimented for about 3 years with making different compost teas and nutrient teas, but there is still a lot of expense $$$ associated with making high quality nutrient teas....like kelp meal, liquid seaweed, rock dust, bat guano, un-Sulfured molasses, worm castings. You can eliminate a lot of this expense by becoming an expert at making high-quality colloidal humus compost, and use your properly made compost as the basis of your hydroponic nutrient solution.

Unfortunately, I have been gardening for over 24 years and I have only just recently mastered this difficult skill....and even then, only because I happened to find a very easy to follow, high quality technique and decided to follow the instructions to the letter. I produced more high quality compost in just one week than I was able to use in a whole year! If you can master the technique, I highly recommend it. It is one of the top 3 things you can do to increase the productivity of your food production efforts, while at the same time decreasing the amount of effort required to grow all of your own food, and decreasing the total cost of operating your food production system.

And when I say decrease operating costs, I mean decrease them to almost ZERO, especially if you are producing your own nutrients...



High Efficiency
Hydroponics

The ultimate solution to eliminate the cost of your hydroponic nutrients: Imagine a hydroponic system that does not require you to buy any nutrients, does not require you to make your own compost, and does not require you to brew your own nutrient tea. Seriously! No cost and no effort as far as providing nutrients to your plants! Plus, at the end of the gardening cycle you harvest all of your garden vegetables, PLUS YOU HARVEST FISH from the system--->

Aquaponics

Click Here to learn more!

This solution is aquaponics. If you are serious about producing all of your own food and being self-sufficient, this is the ultimate solution for reducing expenses (as much as possible), reducing the total amount of work required, and maximizing the productivity of your gardening efforts. I have been gardening for over 24 years, and it is the perfect food production solution in my opinion.


Produce garnden vegetables AND fish together. Eliminate fertilizer costs!

Besides mastering how to make high quality compost, learning aquaponics is one of the top 3 things you can do to increase your garden productivity, reduce your total costs, and reduce your total work. The product that I learned from is called Aquaponics4you. With all of my hydroponic gardening experience, the first time I came across the Aquaponics4you product I knew immediately that it was something very special! Place an aquaponics system outdoors and use the sun instead of grow lights, and you have reduced every garden expense to nearly ZERO!



The Same System/ 10 Weeks Later!




If you've found this site helpful at all, I would really appreciate it