Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

bulb out ducting.
Water-Cooled Lamp Fixtures
    Water-cooled and air-cooled lamp fixtures are somewhat popular in hot climates. These lamps run cooler and can be moved closer to plants. Water-cooled bulbs are difficult for thermal imaging equipment to detect. Air-cooled fixtures are inexpensive to operate and easy to set up. Keep outer jacket clean and avoid scratching.
    Growers decrease bulb heat by 80 percent with a properly set up water-cooled bulb. The water and outer jacket account for a ten percent lumen loss. Growers make up for the loss by moving bulbs closer to plants. On an average day, a 1000-watt bulb uses about 100 gallons of water to keep cool, if the water runs to waste. To recirculate the water requires a big, big reservoir. The water in the reservoir that serves a recirculating cooling system must also be cooled. Reservoir coolers can easily cost $1000.
No Reflective Hood
    One option is to remove the reflective hood. With no hood, the lamp burns cooler and emits only direct light.
Reflective Hood Study
    I constructed a black room, everything black inside, to measure the amount of light reflective hoods yield. The room was 10 × 10-foot square (3 m2). The floor was covered with black tar paper. Less than three percent light could be reflected from the black surfaces–there was no extra light in this room. Measurements were made every 12 inches (30 cm) on a matrix marked on the floor. The walls had one-foot increments marked.

In this experimental system, a hoodless HID travels up and down vertically between tiered tubes of budding females. Growers are trying every possible means to grow more in less space and get the highest yield per watt.

The Cage from THC BC in Vancouver, BC is one of the most productive gardens per square foot (m 2 ).
    I tested five different lamps: a 1000-watt clear super metal halide, a 1000-watt HP sodium, a 600-watt HP sodium, a 400-watt super metal halide, and a 400-watt HP sodium. I positioned the bulb exactly three feet from the floor. Every lamp was warmed up for 15 minutes before taking measurements.
    The foot-candle readings on the floor were taken every 12 inches (30 cm) and the results posted to a spreadsheet program. I used a simple spreadsheet graph program to present the graphic results.
    The studies show a huge difference between reflective hoods. Some companies do not test their hoods before putting them on the market. To protect yourself and your plants, set up tests like the ones I did here to find out which reflector is the best for your needs.
    When a reflector distributes light evenly, the lamp can be placed closer to plants.
    In general, the larger the wattage of the bulb, the more efficient it is. Since light intensity diminishes so quickly, bulbs must be close to plants. Consequently, more lamps or point sources of light are necessary for even distribution of bright light.

Plants grow in vertical slabs and are irrigated from above in this recirculating garden.
    Operating costs for three 600-watt HPS lamps are lower than for two 1000-watt HPS lamps. The 600-watt lamps produce more lumens for the same amount of money, plus they can be closer to plants. There are also three point sources of light, which evens out distribution.
    A heat vent outlet around the bulb helps dissipate heat into the atmosphere. Excessive heat around the bulb causes premature burnout.
    The studies show the light distribution of several types of light reflectors. The graphs on page 187 clearly show that horizontal reflectors deliver many more lumens than vertical setups.
    Check out the “Light Measurement Handbook” available free on the Internet. The 64-page technical book answers endless light questions. Download the book in a few minutes, photos and all: www.Intl-Light.com/handbook/ .
Reflective Light
    Flat white contains little or no light-absorbing pigment, so it absorbs almost no light and reflects almost all light. Do not use glossy white. It contains varnish that inhibits reflective light. A matte texture provides more reflective surface.
    Foylon is a reflective material that reflects light and heat in an evenly dispersed pattern. It is durable, and it reflects about 95 percent of the light that hits it. The material is plied with rip-stop fiber and is thick enough to act as an insulator. It’s also heat and flame resistant. For more information on Foylon, see www.greenair.com .
Light Footprint of Different Reflectors

     
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How to add light without using more