ExDex1x1
Active Member
*This guide is a work in progress. If you have any information you feel would help improve this guide feel free to send me a message or post below (Sending me a message probably best in case this thread grows to ridiculous lengths, I'll probably stop digging through it at some point.) and I'll be sure to update the post as soon as I can (and of course give my contributors credit!). Enjoy the read and happy growing!*
So I've seen about a million "What kind of fan do I need to cool this light" "What kind of fan do I need to vent this tent properly" threads here, and I'm sure there's a guide on the forums somewhere, but it hasn't been stickied and it definitely isn't being read by majority of the members on this forum. I'm doing this guide on a whim, so I apologize if the organization is a little wacky or if I miss something. Just let me know if there's anything you'd like to see added and I'll pop it in this post.
*This guide is assuming you do not have CO2 tanks running in a sealed tent environment, this is an open air constant flow room where air is constantly being exchanged to replenish your air and CO2 supply naturally without CO2 generators or tanks. If you are using CO2 this is not the method to use, you'll be wasting your money pumping all that CO2 out of your tent the second it's pumped in. Do not do this.*
Terms used:
-Passive Exhaust/intake: Removing/adding air from your room without the assistance of an exhaust fan.
-Active Exhaust/intake: Removing/adding air from your room with an exhaust fan
-CFM: Cubic Feet Per Minute (of air) this refers to the amount of air moved by a given fan. For instance a 500CFM fan will move 500 cubic feet per minute of air.
-Negative Pressure: The air pressure outside of your growing space is greater than the air pressure in your tent, this causes air to passively enter your room through any entry point the air can find.
-Positive Pressure: The air pressure in your room is greater than the external, causing air from inside of your tent to evacuate the room through any point the air can find to flow through.
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Part One: Ventilation Basics-------------------------------------------------------------
Now everyone knows that proper airflow is key to a successful grow for many reasons, having adequate ventilation is necessary to manage air temps, preventing a large number of bug and some mold and mildew infestations, and of course, providing fresh air with good ol CO2 for your hungry ladies.
For the sake of simple mathematics, the example room I will be using for this guide is a basic 10x10x10 grow area. All of the math done in this guide is easily applicable to your space, just replace these dimensions with the dimensions of your room.
So lets say you're growing in this 10x10x10 environment. The first thing you need to know is how much air you need to bring into this space to properly ventilate. The base amount of circulation needed is debatable, I've seen guides that say you need to replace the air in your room every 5 minutes, some say every 2, others say every minute, and I'm sure there are others. For me, I prefer to exchange the air in a room at LEAST every 2 minutes.
Before we jump into the math, I'd like to cover the basics of air exchange. Negative pressure is your best friend. It is far more efficient to remove air from your room than it is to try and force air in to your room. Here's why: When you try to refresh your air by forcing air in, and attempting to use a passive exhaust, you create positive air pressure within your tent. This means that you may be exhausting air at a decent rate, but more often than not it is at a rate lower than what is specified on your fan. A 500CFM fan used as a forced intake, without adequate exhaust, for instance, will actually be pushing significantly less air than 500CFM.
If your passive exhaust is smaller, or even equivalent in size to your intake, the air will not be forced out at a rate equal to the intake, causing positive pressure in your room. Your fan will be attempting to force air in which is at lower pressure than that in your tent, meaning that less air will actually be pulled in than the rated 500 because the lower pressure allows air molecules to spread further out, so each rotation of your fan blade is moving less air than it would if your external air pressure were higher than internal air pressure.
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Part Two: CFM Calculations--------------------------------------------------------
Now onto the math:
Assuming a 10x10x10 area, we need to calculate how many cubit feet of air are in our room, this is a very simple process, simply multiply the dimensions of your room.
10x10x10=1000cuft. So to exchange the air in this room every 2 minutes, we would need at the minimum a 500CFM fan. This is not to say that a 500CFM fan will maintain temperatures in your tent at a nominal level, it IS to say that every 2 minutes, you will have exchanged the entire air content of your room for new air pulled from the exterior of your tent. Many people confuse the optimal air exchange rate with optimal temperature control, these are two very different animals.
If you want to get a little more technical, and save a couple more bucks on your fans, you can also calculate the amount of space taken up by your substrate and other items in the room.
Lets assume again, that we are in the same 10x10x10 room with 1000cuft of air when empty. We're now going to add in two sets of flood tables for our grow. Most of you like to maximize space, and I like to use round numbers for my examples, so lets say you have 2 equal size tables both measuring 3w x 8d x 2h (assuming you aren't putting your tables on the cold ass floor!), our area taken up by tables would be (3x8x2)2=96 cubic feet of space. Now we take 1000-96 and get 904/2 (assuming 2 minute air exchange rate again) and we end up requiring a 452CFM fan. Now a lot of you are thinking, wow that was pointless this fan is barely smaller than the original, but keep in mind that a difference of ~50 CFM can also be a difference of $25 or more, and will of course, be quieter, and use less energy provided you are buying two fans of the same type.
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Part Three: Intakes-------------------------------------------
Now that we've found a fan that is going to properly exchange the air in our room, we need to cover the next topic of airflow: intakes.
Assuming you're using the optimal fan for your room to exchange air every 1-2 minutes, air intake is very very simple: Passive intakes. The negative pressure generated by your exhaust will cause the air outside of your tent to have a natural tendency to disperse into your tent in order to achieve equilibrium. Air is naturally seeking to balance pressure by moving air from high pressure areas to areas of low pressure. Think of this as being in a 10x10 room with 25 people. If you have 25 people all crammed into one corner of this room, you're all going to be miserable and bunched up against each other, naturally you'll want to spread out so you can make yourself comfortable. This means, that we don't need a second fan to pull air in, mother nature will do the work of the fan for us. All you have to do is have an opening in your tent to allow the air to flow in. It's advisable to put either a carbon filter or a HEPA filter (like the ones on your home's airconditioner/furnace.) This will keep any unwanted dust, mold, pollens, and other nasty particulates that you don't want getting to your plants, and make your environment much more stable. The question is: How large should this intake hole be? The answer is simple: You want the intake to be approximately the same size as your exhaust, OR what ever size fits your HEPA/carbon filter. You don't want to have a 10"x10" HEPA filter covering a 3"x3" intake, you'll be wasting surface area on the filter and replacing them much more frequently.
Now that we have our intake and exhaust covered, we need to talk about air circulation inside the room itself. This is generally achieved by the use of oscillating fans. Now you're probably wondering, why, after all that effort in our exhaust/intake system, do we need MORE air movement? The answer is simple. 500CFM is sufficient to exchange your air, but not to MOVE it within the tent. You want your plants to have air constantly flowing over as much surface area as possible. This will discourage the growth of mold, and prevent pesky critters from landing and making a home for themselves on your plants. This is something we don't want for our ladies after all the work we've put into them. Now how much air circulation is enough? This is really easy to gauge. Standard oscillating fans will have anywhere from a 30 to a 90 degree coverage area. You want to add a fan to your room, turn it on, and stand in various locations in your room. If you can't feel a fairly strong breeze coming off of the fan at any location in your room, the inner branches of your plants certainly won't feel it either. Continue adding more fans until you are confident that there is no location in your room (at least where plants are growing, your chair in the corner doesn't need proper air circulation, it'll be just fine.) then you are done adding fans.
---------------------------------Part Four: Exhausts and Stench Control------------------------------------
Now I'm sure a bunch of you saw the exhaust section and immediately were screaming to yourselves "WHAT THE HELL HE DIDNT TALK ABOUT CARBON FILTERS OR OZONE!?!?!?!"
Well, that was for good reason, as exhaust systems are one of the marijuana grower's worst nightmare more often than not, so I decided to have a larger section for them. Everyone is scared that their neighbors will smell something and alert the 5-0 or that the heat from their exhaust is going to be caught on the growers natural enemy: The FLIR.
For those of you who don't know, FLIR stands for Forward Looking Infrared Radar. What this is, is a police tool that shows differences in temperatures, with a *claimed* accuracy of within 1 degree F. This is bad news for everyone, right? We're all totally screwed. Wrong.
FLIR is pretty intimidating technology, but it is SO EASY to defeat. FLIR cannot see through your walls, FLIR cannot see underground, FLIR cant see a lot of things. The easiest way to defeat a FLIR is to place your grow room in a central location in your home. If the heat from your grow room is not touching an outside wall of your home, it is undetectable to FLIR, by the time the heat spreads through all of your home, it will appear to be the normal air temperature of your home. The other way to defeat FLIR is with some creative insulating and duct work.
Insulating your room: If you are growing in an attic, or along an exterior wall of your home (unless you're using LEDs or only a few tiny CFLs), you're going to be giving off a pretty distinct heat signature. The simplest way to prevent this, is to create an air buffer between your grow room and your walls. You want to have space between your tent or DIY grow room and the exterior walls of your home, the more space between the hot air in your tent and the external walls of your home, the more it will dissipate and the less obvious your heat signature will be.
If you're growing in an attic, more often than not your insulation is going to be a crap shoot. At best you might have R-13 standard fiberglass insulation, this does a great job of keeping a little bit of heat out and a little bit of your homes air (cold or hot depending on if your a/c or heat is running) in. Note that growing in an attic is very ill advised. Year round this is going to be the warmest room in your house. Heat from your home during the winter will naturally rise, it ends up in the attic. During the summer, most attics have no vents in them, they're generally much warmer than the rest of your home from lack of air flow, and from being in such close proximity to the exterior temperatures. If you have the option, don't grow here. If you absolutely are dead set on your attic, insulate your room thoroughly. I'd recommend some top quality foil insulation. It reflects heat inwards and dissipates some of the heat that touches it through multiple layers of insulation, and all you have to do is tack it up to your walls /ceiling with a staple gun or nails. Here's an example of the insulation I'm talking about.
Now for the all important topic: Carbon filters on your exhaust.
For those of you don't know, carbon filters are a relatively low cost (in comparison with other methods) of removing odors from the exhausted air leaving your room, so your pesky neighbors don't notify the police about the skunky smell coming from your home.
Now there are many sizes of carbon filters on the market, DIY methods, and all sorts of price ranges. The general rule of thumb is the higher CFM fan you are using to exhaust (and the more cubic feet of space in your room) the larger carbon filter you will need. Carbon works by surface area contact with the air removed from your room, the higher the CFM of your exhaust fan, the less time the air will be spending in your carbon filter, which in turn means you will need a longer carbon filter in order to allow the air to have ample time to get rid of that stanky dank smell. This is kind of a gray area for me, I really don't know what to recommend as a baseline unfortunately since I haven't had experience with enough different size carbon filters to give you a scientific explanation of how large a filter you need. The one thing I will tell you is that if you are venting directly from your exhaust to the outside air, it's ALWAYS better to air on the side of caution. Its always better to have too big of a carbon filter than it is to have the pungent aroma of marijuana spewing from your home. For this reason, I'd recommend buying your carbon filter locally if possible. This way you can take it home, set it up, see if it works, and if it doesnt go exchange that thing asap!
---------------------------------Part Five: Light Traps----------------------------------------
Light traps. Light traps are a very simple concept for preventing light leaks while allowing adequate air flow. For those of you using tents with open passive vents or any passive intake for that matter, these are hugely helpful.
A light trap is very simple and can be made from any number of materials. The basic concept is to block rays of light from entering your room during dark hours while still allowing air in.
A very basic diagram for you here, this can be constructed out of any material from cardboard shoeboxes to lumber to metal, what ever you have will pretty much work.
__ __ <--- assume this is your tent's wall and vent opening.
|----- |
| -----| <---this is the structure you want to build. By staggering inserts inside your box, you assure that light will not be able to enter, while air will flow freely around the dividers. The more dividers you add the
|----- | better protected your box will be from light leaks, generally 3-4 will do the trick. The idea is to keep the dividers very close together. If you spread them out too far, light rays will be able to bend around the dividers and enter your tent, also make sure your dividers have a decent amount of overlay. If you have short dividers, you're not doing anything productive here.
You can also make light traps by using 90degree ducting. By attaching 90s to each other you can block any light. It's recommended to use several 90s and create at least 1 180 degree bend in your trap to make sure you have no leaks. A single 90 will not do the job, anything over 180 should be fine, attaching a 90 to the end of our 180 (facing the opposite direction so you don't run your duct back onto itself and block significant amounts of airflow) is recommended.
-------------------------------------------CO2 Sealed Tent and Timed Exhaust Guide(In progress)-------------------------------------------------------------------------------------
CO2 is one of the best ways to help expedite plant growth and improve your ladies' ability to perform photosynthesis. Carbon Dioxide is one of the main proponents of photosynthesis which helps your plants create basic sugars and form new cell structures. Increasing the levels of CO2 in your garden can help improve your yields vastly and help create denser, more closely clustered bud formations. This portion of the guide will explain the different methods of implementing CO2 in your garden, as well as the different ways of providing CO2 for your plants.
First, you'll need to decide what method of garden you want to be using. There are several ways to use CO2 in your garden, here are the most popular.
----Sealed Room----
The sealed room is fairly straight forward, we skip the previously mentioned intakes and exhausts, and in their place we use air conditioners, humidifiers, dehumidifiers, and carbon filters within our tent to control the environment. Since we won't have an exhaust to remove stale, hot air from our room, we need to bring in an air conditioner. You can find portable ac units at most of your local home improvement and hardware stores, and in some cases your local hydro shop or garden center. The size of the air conditioner you purchase is going to be largely dependent on the space of the room you are growing in. Each AC unit should have manufacturer's recommendations as to how many square feet of space the unit is capable of cooling, keep in mind that most manufacturers assume that you'll be using this unit to bring your room to standard room temperature of around 70-72 degrees, so it's okay to purchase a unit that is slightly below your actual square footage, since we won't be going quite that low in temp. The other thing you'll need to consider is either a humidifier or dehumidifier depending on conditions in your room. If you are using a hydroponic setup, most likely you will need a dehumidifier to compensate for an increased amount of water and nutrient solution evaporating due to slightly higher than normal temperatures that are allowed when using CO2 in a sealed room environment. You'll also need to have a carbon filter, preferably hooked up to your light's cool tube if you're using one (highly recommended in sealed rooms.). The carbon filter will be used to 'scrub' the air in the room of any impurities and other unwanted particulate that may be floating in the air such as dust, dander, or god forbid, pollen.
----Timed Exhaust System----
Using a timed exhaust system is a compromise between the standard air circulation described in the first portion of the guide, and a sealed tent configuration. This method requires quite a bit of guess and testing and a little bit of sweat equity when you've first put it into the works. Instead of having your exhaust and intakes open at all times of the day, you will instead have your intakes and exhaust sealed, and pump the room full of CO2 for a few hours (while your lights are on). When temperatures in your room reach a certain threshold, or when your lights are going to be turned off (most likely temperatures will be the determining factor here.) your exhaust and intake will be turned on, cooling the room, and replacing the air within your room. Keep in mind this tends to get quite a bit more costly than a sealed tent environment since you're constantly purging and refilling your room of CO2. The aim with this style of CO2 delivery is to have your room filled with CO2 during the light hours for as long as possible before temperatures become unmanageable. This means that within your room you'll more than likely want either an excess amount of circulating fans, or an adequate AC unit. You want to have at least 2-3 hours of CO2 saturation before you have to vent the room, ideally, you would want your entire light cycle to be with the room filled with CO2.
----Sealed Tent, Vented Cool Tube----
This is another option available to some growers depending on the layout of your room, this may be an excellent option to use. This setup follows the same guidelines as a standard sealed tent, with one key difference: a carbon filter outside of your room is attached by sealed duct to your cool tube on your lighting fixture, and exhausted out of your tent. This will make temperatures much more manageable within your room while making sure that you aren't pissing away money by pumping CO2 out of your room every few hours. This is an excellent solution for those who are looking to run multiple high wattage fixtures, but don't necessarily have the money to spend on a top of the line AC unit. The only major disadvantage to this method is that you'll require a carbon filter (or hepa filter) for your cooltube, and a 2nd carbon filter to recirculate and 'scrub' air within your tent.
----------Delivery Methods-----------
Now that we've covered the basics of how you'll need to modify your grow room to properly use CO2, let's cover the basic ways of how to generate CO2 levels within your growing environment!
First things first though, we'll need to be able to measure the amount of CO2 within the room. Much like your nutrient solutions, this will be measured in ppm (parts per million), a great place to look for meters online is here.
Now that you've got a meter, it's time to choose a delivery system. The only system (that I know of) that I won't be covering, is the ghetto-rigged yeast sugar and warm water method, since that's useful for basically...no one... If yeast sugar and water are your preferred method for CO2, you probably aren't growing in that large of a space, and CO2 isn't really that large of a factor at this level (not to mention that you could just buy a CO2 tank and have it last for a year instead of spending all your money on baking supplies).
Tanks. Most people tend to go with the tried and true method of getting CO2 directly from a tank, these can be purchased at your local welding supply store, and with a little research you can probably locate a local vendor. When buying a tank, it's key to get a regulator. This will keep the CO2 releasing from the tank at a predetermined level, and will keep you from either wasting money and releasing too much directly from the tanks valve, or under saturating your room by not releasing enough. It basically takes the guess work out of the equation, and makes things much more manageable and controllable. *Warning* Please keep your tanks away from excessive heat and be careful not to drop them. This is a pressurized gas and if you happen to knock the valve off of the top of the tank, you're looking at a 25 pound rocket that can put a decent sized hole in a wall...or your chest.* The obvious down side to this method is that you'll be making pretty frequent runs to refill your tanks, and it can be a pain in the ass depending on how far you live from your distributor. This method is recommended for small to medium size gardens, and for those of you who live very close to distributors and don't mind lugging around tanks everywhere.
CO2 Generators.
CO2 generators work by burning either propane or natural gas, the biggest advantage to these bad boys is that you can connect them straight to your home's gas or natural gas line (make sure your unit is compatible with natural gas if you are planning on using natural gas. Some units may be only compatible with one or the other, and it's best not to ignore manufacturer's instructions when you're fucking around with highly flammable gas.) The downside, is, as usual, the increased initial investment in the unit. These are recommended for medium, to large scale growing operations and warehouse situations.
----------------------Proper Implementation of CO2 within Your Garden-----------------------
Much like your nutrient solution, plants will be able to use only so much CO2 at each stage of growth, excess will not damage your plants, but it also won't help, and this stuff gets expensive!
From seedling through the first 2 weeks of growth you want to keep CO2 levels at approximately 450-650ppm. Normal air can have anywhere from 200-500ppm of CO2 on its own, but in sealed room environments plants can quickly diminish this concentration to 0-100ppm in a matter of hours or even minutes depending on how many plants you have in your garden. Plants are just beginning to grow and will not yet have the surface area to be absorbing a full concentration of CO2.
From 2 weeks on through most of your vegetative growth, you want to keep CO2 levels anywhere from 850-1000ppm. Plants will begin to grow very quickly. Since you're using CO2, you can also run your temperatures slightly higher than normal, and humidity levels should also be run slightly high. Plants kept in high humidity (50-65% depending on strain) will not have to replace water that is being lost through leaves as often if they're receiving ample water from the air around them. This will allow the plant to focus on new growth, rather than maintaining old growth. Temperatures should be kept around 85F during light periods, and 80F during darkness. The low difference between light and dark temperatures will promote tight-knit branching patterns, which will allow you to have maximum yields within a smaller amount of space. Plants will grow more bushy rather than spread out and lanky. If you plan on releasing any predatory insects to prevent spidermites and the like, it is best to do so during your 3rd-4th week of vegetation, while plants are still relatively small. You'll end up needing to release fewer predators than if you wait until you have large plants.
For the last 2 weeks of your vegging, you want to increase your CO2 to around 1200ppm, lower temperatures to 80F/75F for light/dark respectively. Humidity should also be lowered to around 40-55% depending on strain.
During flowering, you want to maintain relatively low humidity (40-55% depending on strain). Maintain previous indicated temps of 80F/75F. Maintain CO2 at around 1500ppm.
When your plants are around 4-6 weeks from finishing flowering, you want to really pump up the CO2. Anywhere from 1600-1850ppm is acceptable, anything above 1850 is most likely going to be waste. Your plants should really begin to show significant resinous growth at this point.
2 weeks before you harvest (about the same time you cut nutrients for hydro users) return CO2 levels to around 400-650ppm. This will prevent your buds from tasting like a piece of gum that got stuck to your shoe and carried around on your heel for a week. Plants will use up majority of the excess CO2 within their leaves, and at this point 650ppm will be more than sufficient for the plants to continue growing without sacrificing bud flavor and smoothness.
As usual, 48-72 hours of darkness with no supplemental nutrients or CO2 is recommended prior to harvest.
-------------------------------------------Cool Tubes and You-Coming Soon!--------------------------------------------------------------------------------------------------------------------------------------
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-------------------------------Updates and Revisions---------------------------------------
02/09/11-Spaced out sections a little more to get rid of some of the wall o' text feel. Added additional information into CFM calculations sections to go a little more in-depth and provide clearer explanation. Will be adding some pictures later this week for those of you who prefer pop-up books to the newspaper. Removed the 'other' info and placed in the post below so people who don't give a crap about the other info can know where to stop reading
Added basic CO2 users guide, more detail to come when my brain is less fried.
So I've seen about a million "What kind of fan do I need to cool this light" "What kind of fan do I need to vent this tent properly" threads here, and I'm sure there's a guide on the forums somewhere, but it hasn't been stickied and it definitely isn't being read by majority of the members on this forum. I'm doing this guide on a whim, so I apologize if the organization is a little wacky or if I miss something. Just let me know if there's anything you'd like to see added and I'll pop it in this post.
*This guide is assuming you do not have CO2 tanks running in a sealed tent environment, this is an open air constant flow room where air is constantly being exchanged to replenish your air and CO2 supply naturally without CO2 generators or tanks. If you are using CO2 this is not the method to use, you'll be wasting your money pumping all that CO2 out of your tent the second it's pumped in. Do not do this.*
Terms used:
-Passive Exhaust/intake: Removing/adding air from your room without the assistance of an exhaust fan.
-Active Exhaust/intake: Removing/adding air from your room with an exhaust fan
-CFM: Cubic Feet Per Minute (of air) this refers to the amount of air moved by a given fan. For instance a 500CFM fan will move 500 cubic feet per minute of air.
-Negative Pressure: The air pressure outside of your growing space is greater than the air pressure in your tent, this causes air to passively enter your room through any entry point the air can find.
-Positive Pressure: The air pressure in your room is greater than the external, causing air from inside of your tent to evacuate the room through any point the air can find to flow through.
-----------------------------
Part One: Ventilation Basics-------------------------------------------------------------Now everyone knows that proper airflow is key to a successful grow for many reasons, having adequate ventilation is necessary to manage air temps, preventing a large number of bug and some mold and mildew infestations, and of course, providing fresh air with good ol CO2 for your hungry ladies.
For the sake of simple mathematics, the example room I will be using for this guide is a basic 10x10x10 grow area. All of the math done in this guide is easily applicable to your space, just replace these dimensions with the dimensions of your room.
So lets say you're growing in this 10x10x10 environment. The first thing you need to know is how much air you need to bring into this space to properly ventilate. The base amount of circulation needed is debatable, I've seen guides that say you need to replace the air in your room every 5 minutes, some say every 2, others say every minute, and I'm sure there are others. For me, I prefer to exchange the air in a room at LEAST every 2 minutes.
Before we jump into the math, I'd like to cover the basics of air exchange. Negative pressure is your best friend. It is far more efficient to remove air from your room than it is to try and force air in to your room. Here's why: When you try to refresh your air by forcing air in, and attempting to use a passive exhaust, you create positive air pressure within your tent. This means that you may be exhausting air at a decent rate, but more often than not it is at a rate lower than what is specified on your fan. A 500CFM fan used as a forced intake, without adequate exhaust, for instance, will actually be pushing significantly less air than 500CFM.
If your passive exhaust is smaller, or even equivalent in size to your intake, the air will not be forced out at a rate equal to the intake, causing positive pressure in your room. Your fan will be attempting to force air in which is at lower pressure than that in your tent, meaning that less air will actually be pulled in than the rated 500 because the lower pressure allows air molecules to spread further out, so each rotation of your fan blade is moving less air than it would if your external air pressure were higher than internal air pressure.
---------------------------
Part Two: CFM Calculations--------------------------------------------------------Now onto the math:
Assuming a 10x10x10 area, we need to calculate how many cubit feet of air are in our room, this is a very simple process, simply multiply the dimensions of your room.
10x10x10=1000cuft. So to exchange the air in this room every 2 minutes, we would need at the minimum a 500CFM fan. This is not to say that a 500CFM fan will maintain temperatures in your tent at a nominal level, it IS to say that every 2 minutes, you will have exchanged the entire air content of your room for new air pulled from the exterior of your tent. Many people confuse the optimal air exchange rate with optimal temperature control, these are two very different animals.
If you want to get a little more technical, and save a couple more bucks on your fans, you can also calculate the amount of space taken up by your substrate and other items in the room.
Lets assume again, that we are in the same 10x10x10 room with 1000cuft of air when empty. We're now going to add in two sets of flood tables for our grow. Most of you like to maximize space, and I like to use round numbers for my examples, so lets say you have 2 equal size tables both measuring 3w x 8d x 2h (assuming you aren't putting your tables on the cold ass floor!), our area taken up by tables would be (3x8x2)2=96 cubic feet of space. Now we take 1000-96 and get 904/2 (assuming 2 minute air exchange rate again) and we end up requiring a 452CFM fan. Now a lot of you are thinking, wow that was pointless this fan is barely smaller than the original, but keep in mind that a difference of ~50 CFM can also be a difference of $25 or more, and will of course, be quieter, and use less energy provided you are buying two fans of the same type.
------------------------------
Part Three: Intakes-------------------------------------------Now that we've found a fan that is going to properly exchange the air in our room, we need to cover the next topic of airflow: intakes.
Assuming you're using the optimal fan for your room to exchange air every 1-2 minutes, air intake is very very simple: Passive intakes. The negative pressure generated by your exhaust will cause the air outside of your tent to have a natural tendency to disperse into your tent in order to achieve equilibrium. Air is naturally seeking to balance pressure by moving air from high pressure areas to areas of low pressure. Think of this as being in a 10x10 room with 25 people. If you have 25 people all crammed into one corner of this room, you're all going to be miserable and bunched up against each other, naturally you'll want to spread out so you can make yourself comfortable. This means, that we don't need a second fan to pull air in, mother nature will do the work of the fan for us. All you have to do is have an opening in your tent to allow the air to flow in. It's advisable to put either a carbon filter or a HEPA filter (like the ones on your home's airconditioner/furnace.) This will keep any unwanted dust, mold, pollens, and other nasty particulates that you don't want getting to your plants, and make your environment much more stable. The question is: How large should this intake hole be? The answer is simple: You want the intake to be approximately the same size as your exhaust, OR what ever size fits your HEPA/carbon filter. You don't want to have a 10"x10" HEPA filter covering a 3"x3" intake, you'll be wasting surface area on the filter and replacing them much more frequently.
Now that we have our intake and exhaust covered, we need to talk about air circulation inside the room itself. This is generally achieved by the use of oscillating fans. Now you're probably wondering, why, after all that effort in our exhaust/intake system, do we need MORE air movement? The answer is simple. 500CFM is sufficient to exchange your air, but not to MOVE it within the tent. You want your plants to have air constantly flowing over as much surface area as possible. This will discourage the growth of mold, and prevent pesky critters from landing and making a home for themselves on your plants. This is something we don't want for our ladies after all the work we've put into them. Now how much air circulation is enough? This is really easy to gauge. Standard oscillating fans will have anywhere from a 30 to a 90 degree coverage area. You want to add a fan to your room, turn it on, and stand in various locations in your room. If you can't feel a fairly strong breeze coming off of the fan at any location in your room, the inner branches of your plants certainly won't feel it either. Continue adding more fans until you are confident that there is no location in your room (at least where plants are growing, your chair in the corner doesn't need proper air circulation, it'll be just fine.) then you are done adding fans.
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Part Four: Exhausts and Stench Control------------------------------------Now I'm sure a bunch of you saw the exhaust section and immediately were screaming to yourselves "WHAT THE HELL HE DIDNT TALK ABOUT CARBON FILTERS OR OZONE!?!?!?!"
Well, that was for good reason, as exhaust systems are one of the marijuana grower's worst nightmare more often than not, so I decided to have a larger section for them. Everyone is scared that their neighbors will smell something and alert the 5-0 or that the heat from their exhaust is going to be caught on the growers natural enemy: The FLIR.
For those of you who don't know, FLIR stands for Forward Looking Infrared Radar. What this is, is a police tool that shows differences in temperatures, with a *claimed* accuracy of within 1 degree F. This is bad news for everyone, right? We're all totally screwed. Wrong.
FLIR is pretty intimidating technology, but it is SO EASY to defeat. FLIR cannot see through your walls, FLIR cannot see underground, FLIR cant see a lot of things. The easiest way to defeat a FLIR is to place your grow room in a central location in your home. If the heat from your grow room is not touching an outside wall of your home, it is undetectable to FLIR, by the time the heat spreads through all of your home, it will appear to be the normal air temperature of your home. The other way to defeat FLIR is with some creative insulating and duct work.
Insulating your room: If you are growing in an attic, or along an exterior wall of your home (unless you're using LEDs or only a few tiny CFLs), you're going to be giving off a pretty distinct heat signature. The simplest way to prevent this, is to create an air buffer between your grow room and your walls. You want to have space between your tent or DIY grow room and the exterior walls of your home, the more space between the hot air in your tent and the external walls of your home, the more it will dissipate and the less obvious your heat signature will be.
If you're growing in an attic, more often than not your insulation is going to be a crap shoot. At best you might have R-13 standard fiberglass insulation, this does a great job of keeping a little bit of heat out and a little bit of your homes air (cold or hot depending on if your a/c or heat is running) in. Note that growing in an attic is very ill advised. Year round this is going to be the warmest room in your house. Heat from your home during the winter will naturally rise, it ends up in the attic. During the summer, most attics have no vents in them, they're generally much warmer than the rest of your home from lack of air flow, and from being in such close proximity to the exterior temperatures. If you have the option, don't grow here. If you absolutely are dead set on your attic, insulate your room thoroughly. I'd recommend some top quality foil insulation. It reflects heat inwards and dissipates some of the heat that touches it through multiple layers of insulation, and all you have to do is tack it up to your walls /ceiling with a staple gun or nails. Here's an example of the insulation I'm talking about.
Now for the all important topic: Carbon filters on your exhaust.
For those of you don't know, carbon filters are a relatively low cost (in comparison with other methods) of removing odors from the exhausted air leaving your room, so your pesky neighbors don't notify the police about the skunky smell coming from your home.
Now there are many sizes of carbon filters on the market, DIY methods, and all sorts of price ranges. The general rule of thumb is the higher CFM fan you are using to exhaust (and the more cubic feet of space in your room) the larger carbon filter you will need. Carbon works by surface area contact with the air removed from your room, the higher the CFM of your exhaust fan, the less time the air will be spending in your carbon filter, which in turn means you will need a longer carbon filter in order to allow the air to have ample time to get rid of that stanky dank smell. This is kind of a gray area for me, I really don't know what to recommend as a baseline unfortunately since I haven't had experience with enough different size carbon filters to give you a scientific explanation of how large a filter you need. The one thing I will tell you is that if you are venting directly from your exhaust to the outside air, it's ALWAYS better to air on the side of caution. Its always better to have too big of a carbon filter than it is to have the pungent aroma of marijuana spewing from your home. For this reason, I'd recommend buying your carbon filter locally if possible. This way you can take it home, set it up, see if it works, and if it doesnt go exchange that thing asap!
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Part Five: Light Traps----------------------------------------Light traps. Light traps are a very simple concept for preventing light leaks while allowing adequate air flow. For those of you using tents with open passive vents or any passive intake for that matter, these are hugely helpful.
A light trap is very simple and can be made from any number of materials. The basic concept is to block rays of light from entering your room during dark hours while still allowing air in.
A very basic diagram for you here, this can be constructed out of any material from cardboard shoeboxes to lumber to metal, what ever you have will pretty much work.
__ __ <--- assume this is your tent's wall and vent opening.
|----- |
| -----| <---this is the structure you want to build. By staggering inserts inside your box, you assure that light will not be able to enter, while air will flow freely around the dividers. The more dividers you add the
|----- | better protected your box will be from light leaks, generally 3-4 will do the trick. The idea is to keep the dividers very close together. If you spread them out too far, light rays will be able to bend around the dividers and enter your tent, also make sure your dividers have a decent amount of overlay. If you have short dividers, you're not doing anything productive here.
You can also make light traps by using 90degree ducting. By attaching 90s to each other you can block any light. It's recommended to use several 90s and create at least 1 180 degree bend in your trap to make sure you have no leaks. A single 90 will not do the job, anything over 180 should be fine, attaching a 90 to the end of our 180 (facing the opposite direction so you don't run your duct back onto itself and block significant amounts of airflow) is recommended.
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CO2 Sealed Tent and Timed Exhaust Guide(In progress)-------------------------------------------------------------------------------------CO2 is one of the best ways to help expedite plant growth and improve your ladies' ability to perform photosynthesis. Carbon Dioxide is one of the main proponents of photosynthesis which helps your plants create basic sugars and form new cell structures. Increasing the levels of CO2 in your garden can help improve your yields vastly and help create denser, more closely clustered bud formations. This portion of the guide will explain the different methods of implementing CO2 in your garden, as well as the different ways of providing CO2 for your plants.
First, you'll need to decide what method of garden you want to be using. There are several ways to use CO2 in your garden, here are the most popular.
----Sealed Room----
The sealed room is fairly straight forward, we skip the previously mentioned intakes and exhausts, and in their place we use air conditioners, humidifiers, dehumidifiers, and carbon filters within our tent to control the environment. Since we won't have an exhaust to remove stale, hot air from our room, we need to bring in an air conditioner. You can find portable ac units at most of your local home improvement and hardware stores, and in some cases your local hydro shop or garden center. The size of the air conditioner you purchase is going to be largely dependent on the space of the room you are growing in. Each AC unit should have manufacturer's recommendations as to how many square feet of space the unit is capable of cooling, keep in mind that most manufacturers assume that you'll be using this unit to bring your room to standard room temperature of around 70-72 degrees, so it's okay to purchase a unit that is slightly below your actual square footage, since we won't be going quite that low in temp. The other thing you'll need to consider is either a humidifier or dehumidifier depending on conditions in your room. If you are using a hydroponic setup, most likely you will need a dehumidifier to compensate for an increased amount of water and nutrient solution evaporating due to slightly higher than normal temperatures that are allowed when using CO2 in a sealed room environment. You'll also need to have a carbon filter, preferably hooked up to your light's cool tube if you're using one (highly recommended in sealed rooms.). The carbon filter will be used to 'scrub' the air in the room of any impurities and other unwanted particulate that may be floating in the air such as dust, dander, or god forbid, pollen.
----Timed Exhaust System----
Using a timed exhaust system is a compromise between the standard air circulation described in the first portion of the guide, and a sealed tent configuration. This method requires quite a bit of guess and testing and a little bit of sweat equity when you've first put it into the works. Instead of having your exhaust and intakes open at all times of the day, you will instead have your intakes and exhaust sealed, and pump the room full of CO2 for a few hours (while your lights are on). When temperatures in your room reach a certain threshold, or when your lights are going to be turned off (most likely temperatures will be the determining factor here.) your exhaust and intake will be turned on, cooling the room, and replacing the air within your room. Keep in mind this tends to get quite a bit more costly than a sealed tent environment since you're constantly purging and refilling your room of CO2. The aim with this style of CO2 delivery is to have your room filled with CO2 during the light hours for as long as possible before temperatures become unmanageable. This means that within your room you'll more than likely want either an excess amount of circulating fans, or an adequate AC unit. You want to have at least 2-3 hours of CO2 saturation before you have to vent the room, ideally, you would want your entire light cycle to be with the room filled with CO2.
----Sealed Tent, Vented Cool Tube----
This is another option available to some growers depending on the layout of your room, this may be an excellent option to use. This setup follows the same guidelines as a standard sealed tent, with one key difference: a carbon filter outside of your room is attached by sealed duct to your cool tube on your lighting fixture, and exhausted out of your tent. This will make temperatures much more manageable within your room while making sure that you aren't pissing away money by pumping CO2 out of your room every few hours. This is an excellent solution for those who are looking to run multiple high wattage fixtures, but don't necessarily have the money to spend on a top of the line AC unit. The only major disadvantage to this method is that you'll require a carbon filter (or hepa filter) for your cooltube, and a 2nd carbon filter to recirculate and 'scrub' air within your tent.
----------Delivery Methods-----------
Now that we've covered the basics of how you'll need to modify your grow room to properly use CO2, let's cover the basic ways of how to generate CO2 levels within your growing environment!
First things first though, we'll need to be able to measure the amount of CO2 within the room. Much like your nutrient solutions, this will be measured in ppm (parts per million), a great place to look for meters online is here.
Now that you've got a meter, it's time to choose a delivery system. The only system (that I know of) that I won't be covering, is the ghetto-rigged yeast sugar and warm water method, since that's useful for basically...no one... If yeast sugar and water are your preferred method for CO2, you probably aren't growing in that large of a space, and CO2 isn't really that large of a factor at this level (not to mention that you could just buy a CO2 tank and have it last for a year instead of spending all your money on baking supplies).
Tanks. Most people tend to go with the tried and true method of getting CO2 directly from a tank, these can be purchased at your local welding supply store, and with a little research you can probably locate a local vendor. When buying a tank, it's key to get a regulator. This will keep the CO2 releasing from the tank at a predetermined level, and will keep you from either wasting money and releasing too much directly from the tanks valve, or under saturating your room by not releasing enough. It basically takes the guess work out of the equation, and makes things much more manageable and controllable. *Warning* Please keep your tanks away from excessive heat and be careful not to drop them. This is a pressurized gas and if you happen to knock the valve off of the top of the tank, you're looking at a 25 pound rocket that can put a decent sized hole in a wall...or your chest.* The obvious down side to this method is that you'll be making pretty frequent runs to refill your tanks, and it can be a pain in the ass depending on how far you live from your distributor. This method is recommended for small to medium size gardens, and for those of you who live very close to distributors and don't mind lugging around tanks everywhere.
CO2 Generators.
CO2 generators work by burning either propane or natural gas, the biggest advantage to these bad boys is that you can connect them straight to your home's gas or natural gas line (make sure your unit is compatible with natural gas if you are planning on using natural gas. Some units may be only compatible with one or the other, and it's best not to ignore manufacturer's instructions when you're fucking around with highly flammable gas.) The downside, is, as usual, the increased initial investment in the unit. These are recommended for medium, to large scale growing operations and warehouse situations.
----------------------Proper Implementation of CO2 within Your Garden-----------------------
Much like your nutrient solution, plants will be able to use only so much CO2 at each stage of growth, excess will not damage your plants, but it also won't help, and this stuff gets expensive!
From seedling through the first 2 weeks of growth you want to keep CO2 levels at approximately 450-650ppm. Normal air can have anywhere from 200-500ppm of CO2 on its own, but in sealed room environments plants can quickly diminish this concentration to 0-100ppm in a matter of hours or even minutes depending on how many plants you have in your garden. Plants are just beginning to grow and will not yet have the surface area to be absorbing a full concentration of CO2.
From 2 weeks on through most of your vegetative growth, you want to keep CO2 levels anywhere from 850-1000ppm. Plants will begin to grow very quickly. Since you're using CO2, you can also run your temperatures slightly higher than normal, and humidity levels should also be run slightly high. Plants kept in high humidity (50-65% depending on strain) will not have to replace water that is being lost through leaves as often if they're receiving ample water from the air around them. This will allow the plant to focus on new growth, rather than maintaining old growth. Temperatures should be kept around 85F during light periods, and 80F during darkness. The low difference between light and dark temperatures will promote tight-knit branching patterns, which will allow you to have maximum yields within a smaller amount of space. Plants will grow more bushy rather than spread out and lanky. If you plan on releasing any predatory insects to prevent spidermites and the like, it is best to do so during your 3rd-4th week of vegetation, while plants are still relatively small. You'll end up needing to release fewer predators than if you wait until you have large plants.
For the last 2 weeks of your vegging, you want to increase your CO2 to around 1200ppm, lower temperatures to 80F/75F for light/dark respectively. Humidity should also be lowered to around 40-55% depending on strain.
During flowering, you want to maintain relatively low humidity (40-55% depending on strain). Maintain previous indicated temps of 80F/75F. Maintain CO2 at around 1500ppm.
When your plants are around 4-6 weeks from finishing flowering, you want to really pump up the CO2. Anywhere from 1600-1850ppm is acceptable, anything above 1850 is most likely going to be waste. Your plants should really begin to show significant resinous growth at this point.
2 weeks before you harvest (about the same time you cut nutrients for hydro users) return CO2 levels to around 400-650ppm. This will prevent your buds from tasting like a piece of gum that got stuck to your shoe and carried around on your heel for a week. Plants will use up majority of the excess CO2 within their leaves, and at this point 650ppm will be more than sufficient for the plants to continue growing without sacrificing bud flavor and smoothness.
As usual, 48-72 hours of darkness with no supplemental nutrients or CO2 is recommended prior to harvest.
-------------------------------------------Cool Tubes and You-Coming Soon!--------------------------------------------------------------------------------------------------------------------------------------
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------------------------------------------------------------------------------------Updates and Revisions---------------------------------------
02/09/11-Spaced out sections a little more to get rid of some of the wall o' text feel. Added additional information into CFM calculations sections to go a little more in-depth and provide clearer explanation. Will be adding some pictures later this week for those of you who prefer pop-up books to the newspaper. Removed the 'other' info and placed in the post below so people who don't give a crap about the other info can know where to stop reading
Added basic CO2 users guide, more detail to come when my brain is less fried.
