The Two Most Efficient
Garden Exhaust Fans

Every indoor garden should have two kinds of fans: garden exhaust fans and air circulation fans. As you can tell from their names, each kind has it's own special place in the garden. In this section, we will take a look at appropriate exhaust fans, but before we do let us first discuss the difference between exhaust fans and circulating fans, and explain why circulating fans should not be used as exhaust fans in your garden.

The Difference Between Garden
Exhaust Fans and Circulating Fans

Exhaust fans are for removing hot, moist air and bringing in cool, dry air (and a fresh supply of CO2). Centrifugal fans are the most efficient
Oscillating fans do not make good exhaust fans, although air circulation is necessary to help each leaf exchange gasses (breath)

Basically, the difference between the two is how much air volume the fans are capable of moving and how efficient the fan is at moving the air. Air circulation fans have a much smaller capacity to move air. This capacity is called a CFM rating, which stands for cubic feet per minute. Anyone who has measured their grow room and gone to the exhaust fan calculator will realize just how much air your garden exhaust fans need to be capable of moving.

The other quality to look for in an exhaust fan, efficiency, is a little harder to figure out if all you have to go by is the information that came with the fan. Efficiency is the ability of a fan to pull air through obstacles. For example, if you attach a small oscillating fan to a long, 6 inch exhaust run, air pressure accumulates in the exhaust run.

Once pressure exists, the blades of the oscillating fan may be turning but very little air is actually being sucked out and exhausted. Oscillating fans DO NOT make good exhaust fans. On the other hand, a good centrifugal fan can develop enough pressure in the system to pull your air through a Carbon filter and still exhaust it. Air pressure is not a problem with centrifugal fans, and one very big reason why they make good exhaust fans.

As a general rule, your exhaust fan (or fans) should be able to exchange the entire air volume of your garden area in less than 5 minutes, although 3 minutes or less would be better.


Exhaust Fans

A direct path through the fan creates less resistance, making the centrifugal fan (on the Right) much more efficient

There are two types of fans that are commonly used as exhaust fans for a garden. These are squirrel cage fans (left) and centrifugal fans (right). Squirrel cage fans scoop air from the side and bat it out the front. You can see from the picture how the air exhaust from the squirrel cage fan is at a right angle to the direction of the air intake. This forces all the air to change directions in the process, which is one reason why they are less efficient than centrifugal fans.

Carbon filters are the most efficient and effective way to deal with unwanted odors. The CFM rating of your Carbon filter should be close to the CFM rating of your exhaust fan

The centrifugal fan on the other hand intakes and exhausts air in a straight line. While both garden exhaust fans work well to exhaust an indoor garden area, only the centrifugal fans are capable of running efficiently at the pressures required to pull air through a carbon filter. So, if you intend to use a carbon filter now or in the future, your best choice would be to buy a centrifugal fan. Some Carbon filters come with a pre-filter of some sort, which greatly increases the life of the Carbon filter.


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check out the Exhaust Setup Page


Consider some important things about your Garden Design


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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.

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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.

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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.


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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!




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