Heating and Cooling
Heating and/or cooling you grow room is important for good plant growth. It’s not only important to have good lighting. But photosynthesis is a major factor in plant growth, and for good photosynthesis to be able to take place within the plant tissue/leaves, temperature is an important factor that affects the process of photosynthesis. Thus temperature dramatically affects whether you get quick healthy plant growth or not. Typically plants are grouped into one of two groups, “winter corps” or “summer crops.” Winter crops like lettuce, and winter squash do better in cooler environments than summer crops do.
The easiest way to keep track of your grow room temperature is with a weather station. Sound expensive? Their not, although there are many types of weather stations, but even the most basic ones record both high and low temperatures, as well as show humidity. The more expensive ones have other features like wind speeds, a rain gauge, lightning detectors, but expensive features aren’t useful in your indoor grow room anyway. For $40 at Wal-mart, I got a weather station that has a wireless remote sensor, that shows temp and humidity in both locations, as well as records the highest, and lowest daily temperatures. It even has a barometer (though not really useful in a grow room). The remote sensor works up to 100 feet away, and can be placed in the grow room.
The weather station base can be placed anywhere in your house (within 100 feet of the remote sensor), and you can view the conditions in your grow room at a glance without even going in the grow room. The temp and humidity can also be read right on the remote sensor that’s in the grow room. You can even get a weather station with more than 1 remote sensor, and place them in various areas of your grow room.
Controlling the temperature in the grow room doesn’t need a expensive computer program either. Through a little trial and error, and using a space heater, or small window AC unit, it won’t be difficult to figure out the optimum timer settings for the consistent temperature range you want. Another inexpensive, yet more advanced option is to use a typical household digital thermostat for your grow room. If coarse you’ll need some wiring knowledge, have a friend that does, or need hire a professional to set it up. But a simple digital thermostat can be programmed to turn on and off your space heater/AC unit (even fans for ventilation) at the specific temperature ranges you want, the same way it does for your house.
For plants to be able to grow, they need to be able to transpire freely during photosynthesis. Basically speaking they need to be able to breathe freely. They do this by exhaling water vapor through tiny pores called stoma in their leaves. Plant transpiration is directly related to humidity (as well as temp). To plants humidity is pressure (vapor pressure to be exact), and the more pressure (humidity), the harder it is for the plants to breathe. It comes down to the pressure difference between the surrounding air, and what the plant is trying to exhale. The more water vapor (pressure) in the surrounding air, the harder it is for the plant to exhale it’s water vapor (like asthma for plants).
The plants need to be able to exhale the water vapor (transpire), in order to be able to uptake water and nutrients through the roots. That’s because water moves through the plant by diffusion. Therefor being pumped up through the plant as it transpires. Bottom line, if they cant breathe/transpire, they wont be able to uptake water and nutrients, and thus they wont be able to grow. Most plants do fine between 55% and 75% humidity, but it’s best to find out the humidity preferences for the crop you plan to grow. Nutrient deficiency can show up in plants in high humidity, because they cant uptake the water/nutrients they need to grow. But nutrient deficiency’s can also result in low humidity as well, because water and nutrients are pumped through the plant too quickly. Where more nutrients make it to the leaves than properly to the fruit.
Humidity in your grow room is a bit harder to control accurately without humidity specific sensors. But with some regular observation, it can be predicted and adjusted. As the plants transpire the humidity will go up, and ventilation is the best cure. In some extreme cases the help of a dehumidifier may be helpful as well, and can be set on a timer when humidity levels are predicted to be high. Low humidity levels are unlikely in a grow room/greenhouse, but can be adjusted the same way with a humidifier during times of predicted low humidity.
Like all life on our planet, plants are a carbon based life form. Carbon makes up the bulk of the plants tissue, and without carbon the plants simply wont be able to make new plant tissue, therefor wont be able to continue to grow. But plants don’t get carbon from the roots and nutrient solution, they get it from the atmosphere. CO2 (Carbon Dioxide) is naturally in the atmosphere at about 3% on average. This greenhouse gas is where plants get the carbon they need to grow new plant tissue. But in an enclosed grow room, or greenhouse plants can use up all the carbon in the air within hours, especially if there’s a large number of plants in it.
CO2 enrichment can be done using CO2 generators, which are basically just controlled natural gas or propane burners. Or with bottled CO2 that you can get at most welding supply houses, or places that sell equipment to make your own beer, they use it for carbonation. But either way CO2 enrichment systems need CO2 sensors and regulators to work efficiently. The investment in equipment can be beneficial, however can be pricey. But fortunately if you provide enough ventilation that brings in fresh (CO2 enriched) air into your grow room, CO2 enrichment equipment isn’t really necessary. Providing good ventilation with plenty of fresh air, is the key to low cost grow room CO2 enrichment, along with many other grow room issues.
Indoor Gardening with CO2/Carbon Dioxide for hydroponics
Environmental Control Systems
DIY Homemade Hydroponics – Climate Control (video)
Plant Growth Factors: Photosynthesis, Respiration, and Transpiration