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News and Best Practices

Add Reflective Surfaces to Your Grow Room

October 19, 2016

Cannabis plants need extremely intense light to produce prodigious quantities of firm, dense buds. Professional growers often use high intensity discharge (HID) metal halide bulbs for the vegetative stage and high pressure sodium HID bulbs for the flowering stage.

Operating these high wattage bulbs is an expensive proposition, and valuable light can scatter if it’s not redirected onto the plants. So, using a reflector hood around each bulb avoids wasting light.

But reflectors may not be enough. It’s sometimes necessary to add reflective walls and a reflective ceiling, which can be difficult to do in a large grow room. Framing the walls and ceiling then sheeting with drywall converts a very large space into one or more smaller spaces. Then, by covering the walls and ceiling with a reflective surface, almost all of the light that escapes the reflector hood can be captured and redirected.

In addition, it’s much easier to control the climate in a smaller enclosed space. But if the idea of compartmentalizing large spaces sounds like an enormous task, you can surrounded them with lightweight wooden frames and attach a reflective surface. Or sheets of a reflective material can hang around the edges of the grow room.

To capture the maximum amount of stray light, walls and ceiling should be covered with a reflective surface, such as white paint or film. White paint has almost no light-absorbing pigment and reflects the majority of the light that shines on it. Flat titanium white is the brightest shade of white and reflects the most light.

Instead of paint, reflective films like Mylar and Foylon—and even aluminum foil—can be applied to the walls.

  • Mylar is relatively inexpensive, relatively easy to apply, and reflects up to 98 percent of the light that shines on it. Because Mylar is manufactured as a thin, smooth film, it must be kept tight when applying it to the walls and the ceiling to reduce wrinkling.
  • Foylon is a reflective material with a textured surface that is designed to reflect light and heat in an evenly dispersed pattern. It’s very durable, since it contains rip-stop fibers. It’s thick enough to be used as insulation. But best of all, it reflects up to 95 percent of the light that reaches it. It must be kept clean to maintain its efficiency; it should be cleaned once a week at the same time you clean light bulbs and the inside of reflector hoods.
  • Lining walls with aluminum foil is better than having no reflective surface at all, but it reflects only 70-75 percent of light. Also, the foil inevitably crinkles during installation, which causes it to reflect light in the wrong direction.


By Bill Bernhardt
Cannabis Cultivation Today articles are for informational purposes only and should not be considered legal guidance or advice on grow practices. You should contact an attorney or a qualified cultivation consultant for specific compliance and cultivation advice.
© 2016 CAN Performance Group, LLC. All rights reserved.

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