A compact, wall-mountable greenhouse named Lada orbits Earth on board the International Space Station, while a sprawling, 36-acre greenhouse lies outside Greater Vancouver in British Columbia. You may never purchase flowers -- popular greenhouse plants -- but you still might benefit from greenhouses that grow food. Regardless of size, structure or location, greenhouses provide a controlled environment where light helps keep plants warm and thriving in ideal growing conditions.
Greenhouses and the Greenhouse Effect
If you ever sat in a hot vehicle with windows rolled up in the summer, you witnessed the greenhouse effect in action. In a greenhouse, radiant energy passes through transparent material into an area where plants, soil and other objects absorb it. They then re-radiate that energy in the form of infrared heat. Because infrared has longer wavelengths, it cannot go out back through the material through which it came. When this happens in Earth's atmosphere, carbon dioxide absorbs that heat and the planet warms. When it occurs in a greenhouse, the trapped heat warms the plants and soil.
Too much sunlight in warmer regions can raise greenhouse temperatures high enough to slow down a plant's growth rate, reduce flower size and cause other unwanted effects. Passive ventilation systems consisting of vents in the top of a greenhouse help remove excess heat. Other types of ventilation systems, such as fan-and-pad evaporative coolers and force air exhaust fans, remove excess greenhouse heat more efficiently than passive systems.
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Advanced Greenhouse Technology
Solar greenhouses, like regular greenhouses, use the sun's energy to heat plants. A solar greenhouse also stores heat that plants can use when no sunlight exists -- such as when it's cloudy or night. Solar greenhouses may exist as standalone structures or attached to barns and houses. Active solar greenhouses use additional energy sources to transport heated water and air from one part of the greenhouse to another. Passive solar greenhouses are good choices for smaller growers because those greenhouses only rely on sunlight for heating. However, growers may need to install electric or gas heaters if they live in colder regions or locations where clouds may obscure the sun frequently.
Additional Greenhouse Tips
Smaller greenhouses don't have to use sunlight as an energy source. Fluorescent bulbs provide light that International Space Station's Lada greenhouse uses to warm plants. In addition to glass, greenhouses may use clear plastic panels and other transparent materials through which sunlight enters. Glass has several advantages, such as allowing more light to pass into a greenhouse, reducing plant disease and lowering humidity. However, glass has more leaks than plastic and higher initial costs. Adequate sunlight is, especially in the morning, essential to healthy plant growth. Daytime Temperatures of 70 to 80 degrees Fahrenheit work well for most plants -- nighttime temperatures should be a little lower.