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Air - Understanding Your Grow Room Atmosphere |
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| A two part article about the composition of air and the need for grow room extraction. Also includes a brief introduction to air exchange using a Klimavator fan speed controller. Downloadable datasheet also available. |
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Air - Understanding Your Grow Room Atmosphere
There are two sections to this article about Air. Section 1 looks at the properties, composition and behaviour of air and the way in which your plants respond to atmospheric conditions. Section 2 is a brief overview of how to set-up an air exchange system for your grow room using a Klimavator Fan Speed Controller. A downloadable version of this article including illustrations is available here.
Section 1. What is air?
Air, generally termed 'atmosphere' is the gaseous envelope surrounding this planet. It is composed mostly of a mixture of gases but also contains solid and liquid particles. The two main catagories are:
Non Variable components
Oxygen (21%)
Nitrogen (78%)
Other gases like: Argon, Neon, Krypton, Hydrogen, Xenon, Radon in very small amounts.
Variable components
Carbon Dioxide (0.03% variable)
Water (vapour, liquid) Dust, Smoke, Smells.
Oxygen and Nitrogen constitute 99% percent of the air and as such the laws of physics affect them as they do any other gas or liquid. This means there is a direct relationship between temperature, pressure, volume and density. Any change in one means a corresponding change in all the others. The change is always the same and predictable. By understanding the relationships between each of these factors and the effect that atmospheric changes have on plants, we can better optimize growing conditions and improve the growing environment.
The Relationship between temperature, pressure, volume and density.
When air is heated its volume increases (it expands) and its density decreases and thus there is a fall in pressure. Humidity decreases in this instance.
Conversely when air is cooled its volume decreases and its density increases and thus there is an increases in pressure. Humidity increases in this instance.
Please see the downloadable version of this article for a diagrammatical representation of these principles.
Moisture in the air.
When we use high output lights, a lot of heat is created. As we know, increasing the temperature of the air in the grow room makes the air expand, but if that expanding parcel of air has a specific amount of water in it then when it expands it's Relative Humidity (RH) will decrease making the air dry. This makes good air exchange essential to maintain the optimum relative humidity for plant growth.
Conversely, when a parcel of air is cooled it contracts while still containing the same amount of moisture, the relative humidity of the air would increase. If cooling continues the air will eventually reach the dewpoint temperature, at which point the air becomes totally saturated and visible moisture droplets start to form. This is why sometimes you get condensation in your grow room after the lights go off and the room cools. Again, good air exchange can minimize the effects of changes in humidity on your plants. The downloadable version of this article includes an illustration that shows how the expansion and contraction of the air in your grow room affects the relative humidity.
It is relatively easy to control your humidity by installing a good air exchange system in your grow room. Try to use input air for your grow room from an inside source where temperatures are friendly, this will help avoid environmental problems. Using cold input air from outside during colder months can cause dry rooms when lights are on and wet rooms when lights are off.
Carbon Dioxide.
A variable component which is essential for photosynthesis and vital to the success of your indoor crop. In the controlled environment of the grow room, we can increase levels with a CO2 vapour release bottle and release kit. Normal atmospheric levels are around 350ppm. Air inside a lived in home can be as high as 800ppm just from people breathing. Another good reason to use input air to your grow room from indoors.
Good CO2 levels are important as the plant leaves, through a process of photosynthesis, use light to combine CO2 and H2O to make carbohydrate (food). This means good air exchange is needed to keep levels up.
Conclusions
If we were to think about it logically (bearing in mind the effect heat (light) has on the air), the best way of maintaining the optimum growth conditions that we want in our grow room is to bring air into the room as close to the desired temperature and humidity as possible. We also want to get it in and out of there as quickly and practically possible on a continual basis. This allows for small changes in the properties and composition of the air in the grow room, keeping temperatures and humidity within normal levels and avoiding extremes. It would also be important to keep the air exchange going when the light goes off, to avoid over humidity or condensation during this period as the air cools.
Section 2. The simple method of air exchange control with Klimavator
The Klimavator Fan Speed Controller is a brand new piece of GroWell equipment that has made temperature and fan speed control much easier for the indoor gardener. It is capable of controlling the speed of both an input and extractor fan of any size (right up to our largest Acoustic Fans) with a built in temperature override. This means that you can specify two fan speed controlling factors. First you specify your “idling” speeds for your two fans (the speed at which you need them to turn over normally to maintain air exchange). Then you set a maximum temperature that you do not want your grow room to exceed. What then happens is that when your grow room temperature gets above the specified point, both of your fans will “kick-in” at their full speed and reduce your temperature below the set point. Once your temperature is under control, you fans will revert back to their “idling” speeds.
KlimaVator Operation
1 Set the desired temperature via the KlimaVator control panel.
2 After power is applied the fan idling speeds can be set via the front panel controls. One speed control for each fan (input and output)
3 As soon as the specified temperature is reached, the two fans will increase to full speed until the temperature falls back below the set point.
4 Fan speeds will then revert back to their idle speeds.
Note:
The input fan is usually slightly smaller than the output fan.This works well as a general principle, ensuring no odours are pushed out of the room, but instead all sucked out through the filter. Also, there is usually extra ducting and filters on the output end of your extraction system and the flow rate of the extractor may be affected a few percent. The input fans are not normally affected in this way as there is not usually any ducting involved.
Ideally you need to be using an input fan with between 0% to 30% less flow rate than your extractor fan and don't seal the area so any extra air needed into the room can come in through holes or gaps. This method also helps keep control of humidity levels with lots of healthy transpiring plants.
Air - Understanding Your Grow Room Atmosphere can be downloaded by clicking here. The downloadable document includes a number of illustrations that help to explain the principles explained above. This document is in pdf format and requires Adobe Acrobat Reader to open it. The latest version of Acrobat Reader can be downloaded from www.adobe.com
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