What do we mean by ventilation

Along with lighting and a nutrition program, proper ventilation is one of the most important things to consider when growing plants indoors.
Outdoor plants enjoy the effects of light breezes, sunlight, fumes and rainfall. Inside we replace this breeze with artificial ventilation, instead of sun we use lamps, and instead of rain - irrigation systems.
Why do we need to ventilate the growth spaces? There are many reasons for this:

1. Removes excess heat

Growth lamps generate heat. It may not seem like much, but a few degrees of temperature difference can mean a difference between a successful and a less successful growing plant. Some luminaires emit more heat than others, but all types emit enough to have a reason to install ventilation.

2. Controls Humidity

Humidity control plays a huge role in plant health. Excessive humidity can cause various diseases or create conditions for the development of insects and other pests. Too low humidity will negatively affect growth, so we must monitor and control it at all times. The plants evaporate water throughout the day, which increases the humidity throughout the room. Evaporation is a process in which the leaves transfer water to the atmosphere. Like a straw, the suction created by the "sweating" of the leaves pulls the nutrients through the roots upwards and so the plant evaporates more. A good ventilation system also removes some of the water released during evaporation from the leaves, allowing the plants to absorb even more water and raise more nutrients up the stem, boosting growth. Therefore, when plants dry up, they stop growing because there is no water to drive nutrients from the soil through the roots and from there to all plant tissues. On the other hand, as already mentioned, too much moisture creates conditions for diseases and pests and prevents absorption through the roots, because it limits the ability of the plant to evaporate. For this reason, the ability to easily increase and decrease the humidity in the growth room is of great importance.
Reducing humidity is easy. All you have to do is get the humid air out using an outlet fan, provided that the air that enters from the outside has a lower percentage of humidity than the one that comes out. You can also install a dehumidifier.
Sometimes in the growth process there are moments when the relative humidity needs to be higher. Sealing the tent or temporarily turning off the outlet ventilation will increase the humidity relatively quickly. Find out what the preferred humidity is for the specific type of plant and try to maintain the norm. Also keep in mind that the larger the plants, the more water evaporates, so as you grow, you may need to pay more attention to humidity levels.

3. Prevention of diseases and pests

Air circulation protects against diseases and pests. Mold, mildew, mites and flies prefer stagnant air and humid conditions. Pests lay their eggs in the moist top layer of the soil, so the fan that keeps the surface layer dry can slow down their reproductive cycle, and the constant breeze makes it difficult to establish them on the plants themselves.

4. CO2 control

Plants need new air for one main reason: CO2. The absorption of carbon dioxide during the day is part of their food cycle. If your tent is sealed, it means that the level of CO2 in the room is gradually decreasing, which limits growth. Ventilation brings fresh air, respectively fresh carbon dioxide from the outside and removes old stagnant air, which enhances the growth and therefore the harvest of the plant.

5. The benefits of wind for the strength of plants

Outdoor plants are constantly blown by the wind. This makes their stems stronger, which serves them well, especially when it comes time to gather their fruit. Healthy and strong plants produce and grow better than weak ones, which can be broken even by the weight of their own fruit.

6. Odor control

One of the main factors in the detection of plants in the closure is the unpleasant space of odor, which goes beyond growth. Advice for this reason should be imposed on many indoor gardeners to use odor control systems that neutralize or eliminate them completely. The most effective methods are to place the filter, the fan or the ozonator.
Designing an efficient exhaust system will be very easy if you take the time to fully understand the idea of ​​airflow in the room. The idea is to create a negative airflow so that the hot air is replaced completely and regularly with new fresh, cool air every day for 1-3 minutes. If you are in a warm area, change the air every 1 minute, if you are in a cool area - every
Well-calculated ventilation allows plants to carry out all the chemical processes involved in gas exchange, along with extracting the heat produced by the lamp, achieving better climate control and therefore growing healthier plants.
Establishing adequate ventilation is an integral part of the design of a closed space extension. Calculating the required ventilation is not complicated at all. Using several formulas, we will translate the entire process of determining how accurate your ventilation should be.
The basic ventilation system consists of several components: an outlet fan, a circulating fan (which rotates the air inside the growth space), in most cases an inlet fan, air ducts and, if necessary, a filter and silencers.

Output fan

The exhaust fan is a key element of any ventilation system, renewing the air and regulating the climate in the growing space.
The required output power depends on both the volume of space used and the lighting used. The brighter the lighting, the stronger the suction fan should be (the same depends on the size of the room). It all comes down to the perfect symbiosis between the individual devices.
It is important to distinguish between conventional conventional extractors (which are all sharp-edged fans) and industrial turbines (RVK, Prima Klima). Industrial turbines are much more efficient. The difference in air flow capacity (m3 / h) between these 2 types of fans is huge!
If you use MH or HPS bulbs, it is strongly recommended to use industrial turbines (RVK, Prima Klima). This type of suction fan also allows the installation of a carbon filter against odors.
There are several rules for the amount of power of the extractor in the direction of space, but none of them takes into account all factors: light output used, current volume and outside temperature.

This table shows what kind of outlet fan you need, depending on the ratio between the growth space and the power of the lighting.
Calculation according to the volume of the room:
As already mentioned, you will find many ways to calculate ventilation, but many of them are inaccurate because they do not take into account the friction losses in activated carbon filters, etc. The following sample calculation is for the minimum requirement for indoor garden ventilation in cubic meters per minute, relative to space. Given that the whole idea is to change the air, it makes sense to calculate exactly how much air needs to be changed.
Step 1: Volume space
Multiply (length x width) x height of the growth space. This will give you the volume in cm3 or m3. For example, d = 2m, w = 3m, h = 2m; (2 x 3) x 2 = 12 m3
Step 2: Recommended cubes per minute
Your outlet fan must be able to adequately change the air completely in the room once every 1-3 minutes. For a room of 12 m3, this is 4 - 12 m3 of air per minute.
We will consider the optimal option for 12 m3 / minute:
12 x 60 minutes = 720 m3 / 1 hour
Another formula that is most commonly used to calculate ventilation, taking into account only lighting, is the following:
(number of lamps x watts per lamp) / 2 + 20%.
2 x 600 = 1200;
1200/2 = 600;
600 + 20% = 720m3 / h approximate requirement for fan power in a room with 2 600W lamps without air-cooled reflectors.
For avid gardeners, we will present the following more detailed description, which includes additional factors:
the minimum requirement is change every 3 min => 12m3 / 3 = 4 m3 / air per minute
4 x 60 minutes = 240 m3 / hour absolute minimum
Step 3: Add additional factors:
For each number of gas-discharge bulb with cooled reflector, add 5% to the minimum requirement for air cooling or 10-20% of the bulb without air cooling.
CO2: add 5% for rooms with CO2 enrichment system.
Filters: If a filter is installed on the exhaust fan - add 20% to the result of the bills made so far (incl.% For CO2 and light bulbs).
Ambient temperature: for hot climates add 25%, in very humid climates - up to 40%!
For example: If you put 2 uncooled 600W lamps in a 12 m3 room and plan to install a filter and CO2 system, the average ambient temperature is 32 ° C, but the incoming air will come from a cooled room and the humidity is high, exhaust fan calculations are the following:
1) Calculate the minimum requirement (see formula above) = 240 m3 / hour
2) x 40% (from 2 x 20%) for 2 lamps with reflector without air cooling.
3) x 5% (due to the CO2 system.)
4) x 20% (for carbon filter).
5) The incoming air will enter from an air-conditioned room, ie we will not add additional percentages for the fact that the temperature outside is 32 ° C.
6) x 40% for high humidity
7) 240 m3 / h + (240 x 40%) + (240 x 5%) + (240 x 20%) + (240 x 40%) = 240 + 96 + 12 + 48 + 96 = 420 m3 / ha absolute minimum for the given conditions and change the air every 3 minutes.
(In hotter conditions the air change should be every 1 minute, ie in such cases we simply multiply the minimum requirement by 3 = 720 m3 / h

One of the often overlooked concepts when it comes to installing an outlet fan system is that a space must be provided for air to enter the growth room. In other words, the operation of the exhaust fan will not be effective if there is no opening for new air to enter from the outside. In the best case, your fan will be overloaded and struggling to try to get air out of the room, provided there is none. In the worst case, the fan will simply spin the same stagnant air with minimal exchange. The crop will be severely damaged in terms of quantity and quality and much more susceptible to infections with diseases, insects, etc.

To make sure there is enough inlet air, you need to install a suction port in your grocery store. Everything from a small hole to a gap under the door is enough for fresh air to enter. Some growers prefer to drill extra holes. Many experts believe that the best place for an inbound port is diagonally opposite the outbound port. The reason for the diagonal positioning is to ensure that new fresh air passes through the entire room before being taken outside by the exhaust fan.
Also keep in mind that if you are not sure where you are getting fresh air from, you may need to add a safety net to protect your growing space from insects, other animals, dust or pollen.
Some also recommend placing a circulating fan near the inlet port to help "pull" fresh air, which can be considered an active intake system.
Relying only on an outlet fan to draw new air from the inlet port is called "passive" reception, which is less efficient. Many growers install fans with the same power at the inlet and outlet. If you have to choose between one or the other - the outlet fan is much more important, but adding an inlet fan, the growth of the growth room will be much more efficient, especially in areas with limited natural air flow.

Negative pressure

Negative pressure occurs when the air pressure within a closed growth space is lower than the pressure outside it. This method is considered a passive intake, as the negative pressure caused by the outlet fan makes it possible to suck fresh air through the opening from the room with higher pressure to the room with lower, in order to equalize.

Input fans

If we are talking about smaller spaces, the inlet fan may not be necessary, especially if your outlet system is good (RVK, Prima Klima). In fact, thanks to the strong suction, air will passively enter the growth tent through its side and openings (to avoid light from entering the tent from the outside, put pieces of curved air duct at the openings.)
Of course, the use of an inlet fan is recommended:
For easier air freshening and easier improvement of the indoor climate
In order to limit the negative pressure received from the outlet fan, which "evacuates" the tent walls and thus reduces the growth space and creates a precondition for the release of odor outside the enclosed space.

Carbon filters (or how to protect against odors)

The easiest and most effective way to prevent unwanted odors from escaping the growth space is to use activated carbon filters. They are firmly attached to the outlet fan, by means of connectors / brackets or aluminum self-adhesive tape.
The air coming out of the tent first passes through a filter filled with small carbon pellets and comes out odorless. Filters, unlike most deodorizing systems, do not aromatize the air, but eliminate its odor.

Their capacity must match the force of the air flow of the outlet fan. We have prepared the following examples for you:
100mm 160m3 / h outlet fan = 100mm 225m3 / h carbon filter
125mm 225m3 / h outlet fan = 125mm 300m3 / h carbon filter
125mm 325m3 / h outlet fan = 125mm 300m3 / h carbon filter
125mm 203 / 360m3 / h outlet fan = 125mm 450m3 / h carbon filter
150 / 160mm 425m3 / h outlet fan = 150 / 160mm 400m3 / h carbon filter
150 / 160mm 680m3 / h outlet fan = 150 / 160mm 650m3 / h carbon filter
200mm 750m3 / h outlet fan = 200mm 760m3 / h carbon filter
315mm 1350m3 / h outlet fan = 315mm 1200m3 / h carbon filter
The carbon filters of Prima Klima are 2 series: Eco and Industrial. The eco series has a year and a half of optimal operation of activated carbon, and in the industrial series it is 2 years.
The filter housing is covered with a special cotton wool that traps small particles of air before it reaches the core of the carbon filter, thus avoiding clogging and deterioration of the work of activated carbon. Cotton wool can be changed or washed.
If for some reason you can't or don't want to use filters, there are several other alternatives:
- Ozonizers are one of the most effective options for eliminating unwanted odors. Ozone is a gas (O3) that is generated artificially by activating ambient oxygen with high-voltage electrical charges. This has not only a strong deodorizing effect, but also antimicrobial and oxygen-saturating and is very effective in completely eliminating odors. The ozonator is placed in the room where the growth tent is located (do not place the ozonator in the growth space, as ozone is toxic to plants!)
- Use of deodorizing gel, which, however, must be replaced very often with a new one and has a much weaker effect than the above 2 options.

Air-cooled reflectors

This type of system reduces the heat generated by the bulbs.
Air-cooled reflectors are very efficient devices that connect to the outlet fan, thus evacuating the heat around the lamps outside the tent, even before the temperature rises throughout the room.

Connection options:

Unfortunately, according to some growers air-cooled reflectors have a small disadvantage in terms of the amount of light emitted, which is why they should be used only when necessary (if the temperature is above 28 degrees and there is no other way to be downloaded).
In fact, the glass that makes up the cooling tube (or barrier in Sputnik models) absorbs approximately 10% of the light emitted by the lamp, even more if the glass is not perfectly clean. This loss is even greater in terms of the light reflected in the reflector, as it will have to pass 3 times through the glass before it reaches the plants. Air-cooled reflectors are also usually smaller in area than conventional ones.
According to other gardeners, air-cooled reflectors are much more effective than classic ones because it is possible to place them much closer to the tips of plants without burning them, but it should be remembered that the closer the reflector is to plants , the smaller the roof area. In this way, the benefit will only be for the plants that are directly under the lamp, while the others will receive significantly less light.
What type should the circulating fan be?

The circulating fan complements the operation of the outlet. Although it is not very effective in reducing the temperature, it prevents the stratification of the air in the growth tent.
The indoor (circulating) fan is especially important for plant health, as it acts like the wind in the open and causes:
- Stronger branches and stems, thus gaining the stability so necessary to maintain the weight of the flowers with the end of the flowering phase.
- Better air renewal indoors, respectively better gas exchange of plants.
- Reduced levels of relative humidity, respectively less diseases and pests.
The most common fans in growing spaces are those that are usually used at home in the summer. Rotating fans are much more efficient than fixed ones, which blow in only one direction. Most professionals use 1 fan for each square meter.

A fan with a clip attached to the reflector

There are other interesting fans for indoor cultivation, some of them can be attached to the wall with a screw, others have a stand for the ground, others have a clip, and some have all three options.
Clamp fans are an interesting option because they save space and are very practical. You can easily fix them to the bars in the growth tent or place them between the plants.
Many experts use the Adjust-A-Wing reflector with this type of fan attached to the bulb, thus preventing the formation of hot spots under the lamp, as do CoolTube reflectors with air cooling, but without light loss!
An important condition is to have a ratio between the size of the fan and the size of the plants. Direct ventilation on seedlings or young cuttings is not recommended, as it can dehydrate tender and fragile greenery. During the first 15 days of plant life you should not use a fan directly, but you can not use it completely (the fan should be aimed only at the bulb, or to the wall of the tent). Later, as the plant grows larger, larger circulating fans will be needed. One of the best options is to use fans with speed control systems. Thus, when the plant is small, you can use the lower speed, and then move to a higher one.

Ventilation cycle

Soundproof boxes effectively reduce the noise generated by the fan box. Industrial turbines such as Prima Klima with high-quality motors have less noise than conventional suction fans.
Sometimes the noise caused by these systems can be a problem for some gardeners. Fortunately, there are several ways to reduce it quickly and effectively:
- Using the GSE climate controller (GSE also offers step-up transformers designed specifically for quiet fan start-up).
- Isolation of the extractor by wrapping with soundproofing material.
- Assembling a wooden / metal soundproof box.
- The use of a carbon filter slightly reduces the noise generated by the air flow.
- The use of silent air ducts (quilted inside).
- Installation of silencers (pots) after the outlet fan. They are especially effective when positioned in places where the installation makes a turn.

What kind of air duct do we need?

Flexible aluminum tubes work well for most growing systems. They are affordable and easy to install, but you can also use soundproof aluminum ducts or heavier pipes, depending on your preferences and budget.
The important thing to keep in mind when choosing air ducts is the size. Smaller ducts have greater resistance to airflow, as do most bends and bends along the length of the pipe, so the more air you have to travel, the more it weakens.
How can we improve the efficiency of air ducts?
If you have a flexible aluminum air duct, the first thing you can do is smooth out the "wrinkles". This will increase airflow and generally improve the performance of the duct. You can also redirect the pipe so that there are fewer bends along the length and shorten the length as much as possible.

Adding CO2

Since plants require CO2, it seems logical that we need to do to boost growth is to inject CO2 into the tent. While this is true in theory, there are a few other IMPORTANT things you need to know before you rush to add CO2 to your growth space.
Carbon dioxide injection requires sealing the room for 2 very important reasons. The first is efficiency. CO2 only works at very high levels of concentration, which is not possible if the room is not sealed or your tent is not set up to maintain the highest possible concentrations to make it worth the effort.
The second reason is security. High levels of CO2, which are recommended for plants, are dangerous to humans. You certainly would not want so much carbon dioxide to leak into your home and put you and your loved ones at potential risk.
Before adding extra carbon dioxide, also keep in mind that you need bright light (MH / HPS) so that the plants can fully benefit from the added CO2.
Do you need to add carbon dioxide to your growing space? Adding CO2 is something to keep in mind AFTER you have optimized all other aspects of your ventilation system, because CO2 is most effective when added in an optimal environment. You also have to consider the environment. If you are satisfied with your yields and your budget is limited, you can do without the addition of CO2. On the other hand, if you have a higher budget and you are experimenting with increasing the yield of carbon dioxide, it is worth a try.