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HOME + GROW INFORMATION + CLIMATE CONTROL FAQ

FAQ: CLIMATE CONTROL

How do I know if my humidity level is right for my plants?
I’m concerned, my grow room seems to be very humid. Is this a problem? How do I control this?
My orchids aren’t doing well -their leaves keep shriveling up and wilting. What's going on?
Why do growers add carbon dioxide to their garden? Is it worth it?
How do I add CO2 to my garden? What do I have to worry about?
My thermometer says that my room is 85 degrees F and 65 degrees RH, which I have been told is within the acceptable parameters, but I think I am seeing heat damage, what’s going on?
In terms of environmental conditions, do my plants need anything besides the correct temperature and humidity levels?
Does music really help plants grow?
Is there a simple and easy way to cool my grow space?

Equipment Setup:

I recently purchased a Vortex fan, CAN 9000 Filter and Flange. How do I connect the flange to the filter? Which way should air flow to exhaust heat out?
 
How do I know if my humidity level is right for my plants?
Different plants require different humidity levels. Orchids, for example, prefer a environment of between 55% and 75%, 70+ Relative Humidity (RH) in order to meet their true potential. Seedlings prefer a humid environment as well. Some plants prefer drier climates and if these plants are in the fruit or flowering stage, humidity can become a serious problem.
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I’m concerned, my grow room seems to be very humid. How do I control this?
If you find that the level of humidity in your room is excessive, steps SHOULD be taken to control it. Overly humid conditions can quickly cause the growth of harmful bacteria and fungus. It can also provide the type of environmental conditions for certain pests to attack your plants.

The easiest method is to install a vent fan on a timer. The timer will regularly turn the vent fan on and exhaust humid air. While this will help considerably it is still a very rough method of control. We prefer more precise humidity control and therefore use a vent fan powered by an automated controller which will keep the RH level within a set parameter. The controller will sense the RH level in the room and will turn on the vent fan whenever humidity levels reach too high. It will turn the fan off when the RH level has fallen below your chosen set point. Here’s an example of a controller we like, the HUM-1 from C.A.P.

In a medium to large-scale system, you may find that a vent fan is not sufficient and that a dehumidifier must be employed to solve the problem. Most dehumidifiers you’ll find on the market are not strong enough to handle this sort of situation. They also require regular emptying of the collected water which can be a real pain (although you can and should use this water as it is usually very pure!). We suggest using an industrial-strength dehumidifier which pumps directly to a local drain.

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My orchids aren’t doing well - their leaves keep shriveling up and wilting. What's going on?
It sounds like your orchids are suffering from a dry environment. In Hawaii, orchids grow naturally in the open air because there is so much abundant moisture. This is the environment that your orchids are thirsting for. In summer, the relative humidity should be about 70% during the day and 40% at night, and 50% during the day and 30% at night in winter.

To increase the relative humidity around your plants, place them on a bed of gravel in a water-filled saucer. Place th e pot on the gravel, but do not allow the water to touch the pot, to avoid problems with root rot. A humidifier also gives excellent results. A humidifier can be run with a timer – with the help of a hygrometer you can experiment to find how long you need to run it to achieve the optimum level of humidity. Another alternative (and one which we prefer ourselves) is to run the humidifier with the help of an relative humidity controller such as the HUM-1 from C.A.P. A third option is a humidifier which can be connected to a water supply for continuous running.

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Why do growers add Carbon dioxide to their garden? Is it worth it?
Well, we actually deal with this on another info sheet in detail. But, in general we always say that you should dialall other variables in first before you try and deal with CO2. It throws everything a little out of wack. You want your temperature to raise to around 84-88F (since this higher temperature is needed in order for your plants to metabolize all of this extra CO2 and form it into sugars for the rest of the tissue it will generate,) and because of the fact that the plants are working much harder (and transpiring more water out of their leaves) humidity will rise as well. This opens a whole can of worms.

All this being said, CO2 greatly enhances performance. Carbon Dioxide is a much needed resource for your plants’ development and overall growth. Plants use CO2 in their respiratory cycle, much like we depend on oxygen. Plants can absorb much more CO2 than that which is available at natural atmospheric pressure levels. In most outdoor environments, CO2 is available at 450 parts per million (ppm). Most plants can use anywhere from 1300 to 1600 ppm. This is roughly up to 4X the amount that is available outside. If you give your plants these elevated levels of CO2, you will immediately notice a vast increase in plant growth, development and fruit/production. Plants with elevated CO2 levels will produce, on average 30% more fuit/flowers when compared to plants at normal atmospheric CO2 levels. - That’s a “true” easily attained 30% (as long as all the other enviornmental co-factors are dialed in as well. . .) Check out the Sentinel Controls for CO2. They make it oh so easy and are very affordable for what you get. The CPPM-1 is a Fuzzy Logic CO2 Monitor and Control Unit tht will keep your CO2 levels constantly at 1500ppms and is equiped with a photocel which turns the unit off at night when plants no longer take up CO2. The CHHC-1 from Sentinel will do what the CPPM-1 does (Fuzzy logic CO2 control) with added Humidity / Temperature Control.
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How do I add CO2 to my garden? What do I have to worry about?
The first thing to decide is which method you want to use to enrich your room. The goal is to fill a room with the desired level of CO2 as quickly as possible.

A CO2 Injection System runs off of carbon dioxide gas (much like a soda dispenser) and is a good choice for a small room. The drawbacks to this kind of enrichment system is the need to consistently change CO2 tanks, and the fact that it can often take a long time to enrich a room. It's a great choice for smaller systems. The largest room this system should be used with is 10x10 (and that’s pushing it a little). We've designed a CO2 Calculator to help you figure out how long to run your emitter system.

We prefer to use a CO2 Generator for larger rooms. Generators come in different sizes and you can purchase a generator that is optimum for your room size. (You want a generator that is capable of enriching your room in 5 – 10 minutes.) We have a Calculator to help you choose the correct size generator.

CO2 generators use one of two types of fuel.  You can choose to run it off of liquid propane tanks or a natural gas line.  Liquid propane is fine, but the tanks need to be regularly refilled (which can be a real pain).  Natural gas runs off of a natural gas line, which once installed properly, is safe, low maintenance and easy to use.

CO2 emitters do not add any extra heat to a grow room, although CO2 generators do. Depending on the size of generator you choose, you may be adding a considerable amount of heat to your grow room. This combined with grow lights can create a very warm room indeed. The good news is that heat is a necessary catalyst for plants to use the added CO2 and that they prefer much warmer temperatures than they do without CO2 enrichment. Most plants prefer temps of up 90 – 95 degrees with CO2 enrichment. If your room doesn’t heat up this warm you may need to bring in a heater (this can be the case for greenhouses).  Usually, however, the room will get too hot and an air conditioner will be employed.

Humidity is the second major issue with CO2 enrichment.  CO2 enriched rooms can get extremely wet. This increase in RH is due to the fact that the plants’ metabolic processes are occurring at a more extreme rate and water is flowing up through the roots and out of the leaves quickly. Most plants do not thrive in an overly humid environment. Most plants prefer an environment between 55 and 65 RH. The preferred level of humidity fluctuates as the plants move through their seasons. They will like more humidity in the vegetative stage and less in the fruiting/flowering stage. As the plants grow older, more leaves are produced and more moisture is created. This will become a problem for most growers (although this will vary depending on the environment in which you live; if its dry and warm outside, you probably will have few humidity issues).

When the level of humidity gets too high it needs to be removed with either a vent fan or a dehumidifier. The most common problem for most growers is finding the fine balance between exhausting moist air, enriching a room and keeping the temperature at the right level. If this is done incorrectly, CO2 will be exhausted with the air and plants will not get the benefit of the CO2 enrichment. There are many solutions to this conundrum and we will tell you two of our personal favorites. Feel free to modify these examples to fit your needs.

1. If you are using a CO2 emitter system, we suggest use of the Fuzzy Lgoic CO2 Controller from C.A.P.. It is very affordable, easy to use and extremely efficient. It will turn CO2 enrichment on and off at predetermined intervals, based on basic information you provide. (Room dimensions, desired ppm, output level of emitter) It does all the calculations for you and creates a CO2 on/off schedule coupled together with vent fan control for airing out the room. It will turn the CO2 OFF before it turns the vent fan ON and vice-versa. It comes standard with a photosensor which ensures CO2 will be turned off in the dark period when plants are unable to use it anyway.

2. For larger situations when a CO2 generator is employed, heat and humidity are even more of an issue. In this type of growing situation, we highly recommend the grower invest in the CDMC Package from Green Air, as well as a temperature/humidity controller. For a detailed explanation of how this works, click on the two product links above or click here to see how they work together.

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My thermometer says that my room is 86° F and 65° RH, which I have been told is within the acceptable parameters, but I think I am seeing heat damage, what’s going on?
Your sensors are giving you an ambient environmental reading, which may be very different from what the plants themselves are experiencing. In an indoor environment, powerful HID lamps give off large amounts of intense heat. Depending on what size lights you have and how close they are to the plants, the plants may be experiencing very hot conditions.

To get a true reading of the conditions your plants are experiencing, we suggest using an indoor/outdoor thermometer-hygrometer. The extended sensor allows for placement at the plant tops where temp and humidity reading really matter. If any automated controllers such as thermostats (for example the TEMP-DNe ) or humidistats (like the HUM-1are being used,, the set points can be adjusted to compensate for the difference between ambient and plant level conditions.  A circulatory fan can also be set up to blow across plant tops, thereby removing hot air.

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In terms of environmental conditions, do my plants need anything besides the correct temperature and humidity levels?
Yes. Plants really appreciate a gentle breeze in a grow room. This breeze prevents stale pockets of moisture and heat from building up, while also providing a gentle and stimulating exercise for plant stalks. A gentle breeze will strengthen plants and help them to grow better.
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Does music really help plants grow?
The jury is still out on this one, but some studies have shown that plants respond favorably to classical and Indian music. No Death Metal, please!
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Is there a simple and easy way to cool my grow space?
For cooling, we suggest using a vent fan and coupling it together with a thermostat like the TMP-DNe. When temperatures get too high, the Tempstat will turn the vent fan on until the temperature drops below your chosen set point.

In most indoor environments, lighting is the major source of heat. Air cooling your lights is another possible solution. Most horizontal reflectors can be easily converted to air cooling by using a glass lens, the correct duct flanges, and vent ducting to a good exhaust fan.

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I recently purchased a Vortex fan, CAN 9000 Filter and Flange. How do I connect the flange to the filter? Which way should air flow to exhaust heat out?
The Flange comes with double sided tape.  You apply the tape to the flange and then peel of the tape on the other side and press it onto the filter.  Then you use the self tapping screws that also came with the unit and drill them into the top of the flange (through the flange) and into the top of the filter. These screws need a second to "catch"; but once they do they will go through the remaining metal on both the flange and filter rather easily.

Here is a simple diagram for Exhausting the room with one filter and fan:
http://www.igrowhydro.com/InfoSheets/Diagram-AirCool_NoCO2_SmallHut_EasiestStyle.pdf
Here is an example of Exhausting the Room and Air-Cooling the Light all with one Fan and Filter:
http://www.igrowhydro.com/InfoSheets/Diagram-AirCool_NoCO2_SmallHut.pdf
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