Synthesized from GreenLeaf420 Information at boards.cannabis.com:
While following the basic principles found in a popular gardening books. And the aid of forums an experienced friends, things went pretty well for our gardens. Today, we have to do a little better if we want to stand out and there's a lot more people skilled in indoor cultivation, so it takes a little more to ourserlves and our product from the rest, and if you always do the same thing, you can always expect to get the same results. The first place we look to make a change is in the strain to grow and it's often a great place to start. However, the commercial grower needs to produce what the buyer wants, rather than trying to dictate wha it'd be. So if we aren’t changing the strain of produce we oughtta pay more attention to the details. It’s never just one thing, it’s a compilation of many smaller details.
It's known that a strain will take on different physical appearances and traits when grown in different GR although genetically the strain is the same in either room.
For example
“A commercial propagator produces cuttings from a known and identical mother. Grower “A” purchases a batch of cuttings, standing right behind him is Grower “B” who also purchases some cuttings. They of course have constructed their growing environments independently of each other. During the first weeks the plants appear the same in either location. However, over the course of the crop the differences start to become less subtle and by harvest manifest into two very different looking crops. If Grower “A”’s crop exhibits more of the traits sought after in their marketplace, it’s a sure bet that they will have sold his crop well before Grower “B”, and likely at a premium.”
The two greatest factors that will influence the physical traits of the plant are environment and nutrition. Aside from the strain, the number one factor in distinguishing a premium crop versus “B Grades” is the environment it was grown in. Older style growroom construction allowed people to grow year round with fairly predictable results, but was not short on limitations. Air exchange has been the number one limitation to maintaining and controlling the growing environment optimum for your crop.
Temperatures greater than 85°F are detrimental to overall crop quality in most cases. This temperature should not be exceeded in the plant canopy, directly under the lights, never mind on the thermostat hung on the wall several feet from the nearest H.I.D source. I cannot stress this enough. Yes, plants can metabolize faster under slightly warmer conditions in the presence of elevated CO2 levels, but this tends to contribute to less desirable developmental characteristics and physical appearances.
The first gardening books suggested that the grow-room be outfitted with an exhaust fan that was capable of discharging the entire internal volume of the room in about five minutes. Seems that it was back when gardeners were illuminating an entire 10’ X 10’ room with one 1000W HID lamp. That fan would run near constant during the light cycle, and rarely help to keep the temperature within optimal daytime ranges (75-85°F). Air-cooled reflectors helped growers to reduce heat in the growing environment by removing the heat associated with grow lamps before it ever enters the growing environment. This way, the HID lamps are enclosed in a four-sided lamp reflector, which is sealed from the growing environment by a sheet of satefy glass. Flexible ducting is then connected to the reflector via collars/flanges (two per shade: one in, one out). A fan pushes or pulls fresh, cool, outside air through the shades cooling the lamp(s); discharging the heat from the growing environment before it even enters. Problem solved? Not really.
A labyrinth of ducting is required for multiple light gardens. This takes up a lot of headroom and restricts mobility within the GR. To optimize light levels, the glass safety shields need to be cleaned frequently. An additional intake and exhaust fan and opening(s) are also required. Unless very well insulated, this type of growing environment can be very loud to run and with all the heat being discharged, you may be the only one on the block with no snow in their yard or roof. With all this air exchange(s) It is very difficult to use supplemental CO2 efficiently, as it is typically exhausted away with warmer air. Also you don’t really control the internal temperature of the Grow Room.
The outside air temperature being drawn through the intake vents will dictate just how comfy your crop may be. There is a limitation inherent to all intake applications: you did not help to create the air drawn in. You are at the mercy of fate. Many spores resulting in diseases, insects, and other problems are drawn into perfectly healthy growrooms through fresh air. An activated carbon filter may help to reduce these problems, but will not be effective if outside RH (relative humidity) is greater than 80% and If you use a carbon filter on your intake you will also be restricting airflow potential.
Today, CEA (Controlled Environment Agriculture) has given birth to the “sealed room”. This is now a certified method of producing the highest quality crops on a consistent basis while eliminating many of the problems and downsides associated with the growrooms of yesterday. To acomplish this, Make sure that your GR is very well insulated for sound and temperature. The room must be completely sealed, there should be no light leaking from any cracks, particularly around door frames, etc. All the walls, floor, and ceiling should be lined with a heavy gauge reflective and water resistant material. Six mil black and white poly is still great. It comes in large sheets (10’ X 100’
, so it can be installed in one giant sheet, reducing cracks. All joints should be double sealed with a durable sheathing tape. Remember, the more airtight the better
In a truly sealed room the ballasts will also be housed in the growroom. Preferably, higher up on a shelf out of harm’s way, yet accessible for maintenance and routine inspection. This does create a lot of additional heat in the growroom versus remote ballasts outside of the growing area. However, it would defeat the “sealed” principle of this room to house the ballasts elsewhere. By centralizing the operation, you are consolidating all the variables into one basket.
Since there will be no intake or exhaust, you will need to manufacture healthy air for the growing environment. The first step in maintaining clean, odour free air is an active carbon filter. There are many applications for active carbon filters, in this instance it will be installed with an inline centrifugal fan acting as a “scrubber”. Just sit a eight inch or 10” centrifugal fan on top, plug it in, and let run 24/7. Air from the growing area will be continuously drawn through the activated carbon, and discharged and circulated through the growing environment. The activated carbon will trap unwanted spores (i.e. powdery mildew), dust, odours, and other airborne contaminants.
A de-humidifier is typically required for dark cycles. Note that in a sealed room the DIF (day/night temperature differential) can be controlled very precisely, so there is often less of a drastic rise in humidity from day to night cycles. RH (relative humidity) should be maintained between 45 to 65%. Higher humidity levels (80%) will decrease the effectiveness of the activated carbon scrubber.
You will need to supplement CO2 (carbon dioxide) levels. The most efficient way to accomplish this is to install a CO2 “sniffer”. This device uses an infra-red beam to determine what the CO2 levels are on a second by second basis, and will activate a gas fired CO2 generator or open the solenoid on bottled CO2 to raise CO2 levels to your preset levels. For most crops, carbon dioxide levels are only supplemented during the light cycle. For smaller rooms, bottled CO2 is great especially if the room is well sealed. On larger rooms, the tanks will need to be replenished too frequently to be practical. Gas fired CO2 generators typically use natural gas or liquid propane (LP) for combustion to produce CO2. They do however, also create heat and moisture as a by-product. Newer generators have eliminated the standing pilot light and use a glow plug to ignite the burners when activated. This provides an added level of safety, helps reduce residual heat, and saves some gas consumption. Note: Do not keep propane tanks inside the growing environment for safety reasons.
At the heart of the success of a sealed growing environment is a well planned air-conditioning system (A/C). The best choice for most indoor gardens is a water cooled air-conditioner. Conventional A/C units require an air to air heat exchange. This means that the heat “trapped” by the A/C unit must be vented away. This is somewhat defeating to the “sealed” room, as now there is an active vent (to discharge heat from the A/C). As the name implies, water cooled A/C units use the flow of cool running water to remove the heat from the condenser unit. Basically, all the heat from the growroom can be discharged down the drain. If using a gas fired CO2 generator, and housing the ballasts within the growing environment you should use about 4000 to 4500 BTUs of cooling capacity for each 1000W HID lamp. Your A/C should always have a dedicated circuit, independent of any other equipment.
Once you have set up you room as described above (don’t forget circulation fans) you just need to set your operating parameters, and the gear will do the rest. Best of all your room is now a sealed bunker well removed from the rest of the world. When growing indoors one must, for all intent and purposes, provide the essentials for plant life. Most will pay off for providing proper nutrition, Carbon Dioxide (CO2) and light, the basis for photosynthesis and consequently plant growth.
Any upgrade should not hold consideration if proper attention has not been given to the garden environment. It's the exhaust fan that is one of the most essential and most often ignored pieces of equipment within the growroom. Air movement, through exhaust, can help maintain ideal temperature, humidity and CO2 levels in the growroom. There are a number of problems that can easily be prevented by taking control of temperature and humidity ranges indoors. Air movement has a direct effect on a number of plant processes.
There are a number of reasons why the plant is affected by the gardener’s ability to remove air effectively. The most important is the effect it has on CO2 . Not only in relation to the amount available within the environment, but also to both the amount that can be taken into the plant and the rate at which it is processed. CO2 and light must be present in order for plants to photosynthesize, it uses it to create energy. It is a naturally occurring compound in the air, around 300 ppm. However, with adequate lighting a garden can easily consume the CO2 available indoors within a few hours. By controlling temperature the CO2 depleted air is removed and cool, carbon dioxide rich air is added.
In respect to the stomata humidity and temperature ranges are of great consequence, but it is the latter that is of a primary concern. Just, as it can speed up the metabolic rate in animals, so too can it affect plants. Air temperatures within the range of 65-80º Fahrenheit are usually good parameters to seek within an indoor garden. The upper daytime limit can be raised to 85ºF or more when CO2 is supplemented. In fact, the processing of CO2 is directly affected by temperature. Some experiments have shown a rise of 20-30ºF can increase the rate of photosynthesis dramatically by increasing the speed at which carbon is taken from the CO2 , thus increasing the amount of energy available. Of course this relationship is not infinite! A limit is reached, not too far above the 90º F mark. Once core leaf temperature rises to this point, the stomata will close in order to curtail excessive transpiration. This effectively starves the plant of CO2 consequentially having a disastrous effect on yield.
If kept within range, transpiration will occur keeping stomata open, which will allow the plant to absorb the much needed CO2. When considering transpiration CO2 is not the only concern. With this process occurring throughout the day, a number of gallons of water can be evaporated into a growroom having a direct effect on humidity. Plants that are reacting to higher temperatures attempt to cool themselves through transpiration. Hence, the temperature will increase the rate of transpiration directly affecting the humidity of the environment as well.
Most plants indoors would prefer relative humidity ranges of 40-60 % because it is optimum for CO2 absorption to occur. When RW is beyond the 60% level, the stomata’s ability to absorb it is retarded. A far more serious issue arrives when moist warm air is cooled to low temperatures. This occurs when the light(s) go into the off-cycle, eliminating the heat created by the bulb. When the temperature is left to drop more than 10-15º F in a humid environment condensation occurs. Basically, this temperature change affects the relative humidity or how much water the air may hold. When the drop is too sudden, the volume of air’s capacity to hold water vapour is lowered and water vapour becomes liquid ending up covering the surfaces of the garden room. These water droplets allow a number of fungi and moulds to colonize, powdery mildew being the most common.
It is by moving air that one can take control over the humidity in the room. It can be done in a number ways with various rates of efficacy. Arguable the simplest is to purchase a humidistat and a fan or if warranted a dehumidifier, allowing for establishment of upper humidity controls. By not allowing the humidity to build one escapes excessive condensation. Removing this air is essential, but equally important is moving fresh air throughout the garden canopy.
The foliage of the plants’ is the area where all the aspects mentioned above come into play, and so the air within must be oscillated. By bringing in an oscillating fan or two the gardener will help to mix the air within the room, helping to create more uniform temperature and humidity. By mixing the cooler air from outside the area of the canopy with that within will reduce the humidity around the plants keeping the stomata open. There is additional benefit here, in that this new air is rich with carbon dioxide. It all comes back to the temperature/humidity issue. That is the primary reason for moving air in any garden. It is therefore imperative not to ignore the climate within your growroom even if at times it is tempting to add another light or more additives with any extra money one might have.
One of the trends in the hydroponic marketplace is that growing technologies have become increasingly user friendly. There was a time not too long ago when hobby growers had to be ¼ grower, ¼ engineer, ¼ builder and ¼ electrician. Today small-scale growroom construction is simplified, or can be by-passed altogether with complete pre-assembled growing environments. For the commercial grower things have gotten a little easier, but most still prefer to do-it-themselves.
For high-quality herbs, you will need about one square foot to produce about one ounce of dried bud. Experienced growers can achieve better, depending on the variety. A good size for a small personal garden might range from 2’ X 3’ to 3’ X 5’. After that, we’re talking about walk-in grow rooms because the average person only has a reach of about 36 to 40”. For efficient use of building materials and overall functionality 2’ X 4’ growing areas work well. If you don’t have a lot of vertical height there won’t be a sufficient volume of air to buffer temperatures, so climate control will have to be precise and constant.
You will need to be able to completely enclose the space, providing a light and air-tight environment. You could be amazed at just how bright a ¼” light leak can be in a dark surrounding; like trying to keep the sun hostage in a bathroom closet. Black and white poly is inexpensive and relatively easy to wrap around a closet or crawlspace to close it in. Hold up a small square of cardboard where you staple to prevent the sheet of poly from ripping itself free of your staples. With doorways, cover the opening with a sheet of opaque poly and install a large zipper for an opening. This is the most simple and inexpensive way to address the challenge of constructing a light-tight space, although as far as construction materials go, it’s not especially durable.
To take it a step further you could line the growing area with 6 mil vapour barrier and install an insulative layer. I like the blue sheets of foam. A 1-1/2” thickness is nice to work with because you can create rigid panels with 2” X 2”’s. For maximum insulation and soundproofing you can use ½” thickness plywood. Use two sheets along with some wood lathing to sandwich a ½” of packed fine sand. These sand-filled panels are very heavy to handle and require a fair bit of support. However, you could crank the 1812 Overture in the growing area and be near deaf to it on the other side. Cover the sand-filled panels with a durable and reflective surface.
Providing adequate ventilation can be a challenge when converting extra living space into a growing area. Actually, it can be really quite easy if you don’t mind drilling six inch diameter holes in your wall and stepping over and ducking around labyrinths of ducting. To do this, you will need to enrich the growing environment with carbon dioxide via a tank and flow meter. You will also need an activated carbon filter so that the exhaust from smaller growing areas can be safely introduced into your living space.
The exhaust system may serve to function as: air exchange, heat reduction, and humidity reduction. Your thermostat(s) must control heating and cooling. Air-cooled reflectors will be a must, and you may need to run ducting to draw air to the growing area.
To help keep plants within an efficient size range you can try the following:
• Maintain narrow Day/Night temperature differentials as large swings in temperature can trigger stretching.
• Never let the temperature get higher than 85 degrees Fahrenheit with supplemental carbon dioxide or 75 degrees Fahrenheit using ambient carbon dioxide levels.
• Initiate the reproductive cycle as soon as a root system has become established. You may need to do a minor leaf pruning occasionally to improve air circulation and light penetration in the plant canopy.
• Good plant hygiene is a must when plants are growing in close quarters. Try to use materials that are durable and easy to keep clean.
• Keep a close eye on your nutrient strength around the roots, high ammonium levels can contribute to an increase in internodal spacing. In these types of situations it might be better to go a little under than over with nutrient concentrations. Use a nutrient that can be tailored to your particular growing situation and plant variety.*
• Bend and tie down branches or entire plants as necessary to maximize light and reduce vertical height.
• Use lights higher in the blue spectrum of the photosynthetic response curve as this will help maintain tight internode spacing in certain varieties (often of more Northern origin-thanks Dave and Justin)
A step-up is to use an infra-red CO2 sensor integrated with the climate control system (exhaust fan and thermostats). For most plants, supplemental carbon dioxide is only supplied during the light cycle. With all growing systems operated near living areas, you want to minimize the amount of noise and vibration. This is most easily done by using a high quality enclosed fan. It is better to have a fan with higher-output capabilities running on a slower speed than it is to have a medium to low output fan running at higher speed.
