Horizontal Reflective Hoods

Marijuana Horticulture

by Jorge Cervantes

Horizontal reflectors are most efficient for HID systems, and are the best value for growers. A horizontal lamp yields up to 40 percent more light than a lamp burning in a vertical position. Light is emitted from the arc tube. When horizontal, half of this light is directed downward to the plants, so only half of the light needs to be reflected. Horizontal reflectors are inherently more efficient than vertical lamps / reflectors, because half of the light is direct and only half of the light must be reflected.

Horizontal reflective hoods are available in many shapes and sizes. The closer the reflective hood is to the arc tube, the less distance light must travel before being reflected. less distance traveled means more light reflected.

Horizontal reflective hoods tend t have a hot spot directly under the bulb. To dissipate this hot spot of light and lower the heat it creates, some manufacturers install a light deflector below the bulb. The deflector diffuses the light and heat directly under the bulb. When there is no hot spot, reflective hods with deflectors can be paced closer to plants.

Horizontally mounted HP sodium lamps use a small reflective hood for greenhouse culture. The hood is mounted a few inches over the horizontal HP sodium bulb. All light is reflected down toward plants, and the small hood creates minimum shadow.