Greenhouse lighting: which lamps to choose?
Incandescent Lamps
Often used as spotlights for a single plant or a small group. Lamps should be hung at least 60 cm away from plants. Because they heat up, they must be placed where they won’t interfere with greenhouse work.
Incandescent bulbs used as supplemental light sources.
Incandescent lamps are inexpensive, but their lifespan is shorter than 1,000 hours.
Fluorescent Grow Lamps
These lamps are ideal for seedlings because they traditionally emit light at the blue end of the spectrum, which promotes growth. Since they operate at cooler temperatures, they can be installed 5–10 cm above plants. As plants grow, lamps must be raised accordingly. Fluorescent lamps are fairly efficient and can last up to 20,000 hours.
Fluorescent grow lamps.
T‑8 and T‑12 refer to lamp diameters. Newer fluorescent types emit red spectrum light, encouraging flowering, and can be combined with blue lamps to provide the full spectrum. Full‑spectrum fluorescent lamps are now available. T‑5 lamps produce three times more light than T‑8 or T‑12 while consuming the same energy.
High‑Intensity Discharge (HID) Lamps
These lamps are used to illuminate large growing areas. HID lamps deliver high light output from a ballast, allowing them to be hung high above plants. They emit heat that can burn leaves if placed too close. Hanging height depends on lamp wattage. Reflectors are often used to direct light onto plants.
HID lamp used in a greenhouse.
There are two types of HID lamps: metal halide and high‑pressure sodium. Metal halide lighting produces blue spectrum light, similar to natural daylight, making it excellent as primary lighting. High‑pressure sodium lamps emit red spectrum light, supporting plant growth and helping plants grow straight and healthy. Sodium lamps last longer than metal halide, but for maximum efficiency they should be replaced as recommended by manufacturers. Older lamps may still work but produce less light and consume more energy.
LED Grow Lamps
LEDs balance blue and red light. They are compact, lightweight, and provide high light intensity. LEDs produce almost no heat, making them highly energy‑efficient.
LED lamps for greenhouse plant lighting.
Although their initial cost is higher, especially compared to T‑5 fluorescents, their lifespan averages 50,000–100,000 hours. This makes them one of the best and most cost‑effective options overall.
Tips for Reducing Greenhouse Energy Consumption
Ventilation and heating can become expensive over time, especially in colder regions. To improve efficiency and reduce energy use, consider these tips:• Keep the greenhouse sealed by eliminating cracks and gaps where air can escape. Seal door frames and other openings. Repair holes in foundations, doors, coverings, and vents. Keep doors closed.
• Insulate the greenhouse. When building new foundations, add 2–5 cm of polyurethane or polystyrene insulation at a depth of 45–60 cm. For existing foundations, seal cracks and gaps.
• Add wind protection to the north wall. Plant evergreens or install temporary fences to act as windbreaks.
• Use thermal blankets or night curtains to prevent heat loss at night.
• Perform annual maintenance on heating systems.
• Use HAF fans for air circulation. A tighter greenhouse retains both heat and humidity. HAF fans improve temperature and humidity balance. More on ventilation is covered in this article.
• Maximize heated space and group plants by temperature requirements.
• Use infrared (IR) and anti‑condensation films to reduce radiation losses in polyethylene‑covered greenhouses.
• Use computer‑controlled systems to improve energy efficiency.
• Consider alternative heating sources. Different types of lamps can be used in the greenhouse. For example, the lighting most commonly found in greenhouses is incandescent, fluorescent, high intensity discharge (HID), and light emitting diode (LED). Each of these types offers different levels of performance and efficiency, which is reflected in their price.
Incandescent lamps
Often used as a spot lamp to illuminate a specific plant or a small group of plants. The lamp must be hung at a distance of at least 60 centimeters from the plant(s). These bulbs get hot, so they need to be hung in places where they won't interfere with work in the greenhouse.
Incandescent bulbs are used as an additional source of light for plants.
Incandescent lamps are inexpensive, but they have a lifespan of less than 1000 hours.
Fluorescent grow lamps
These lamps are ideal for germinating plants because they are traditionally at the blue end of the light spectrum, and blue light promotes growth. Since these lamps have a cooler temperature, they can be installed within 5-10 cm. from plants. As time passes and the plants grow, the lamps will have to be raised accordingly. These fluorescent lamps are quite efficient and can offer up to 20,000 hours of use.
Fluorescent grow lamps.
T-8 and T-12 bulbs refer to fluorescent lamps where T refers to the diameter of the bulb. Newer types of fluorescent lamps that emit light in the red spectrum are now available. Such lamps stimulate the flowering of plants and can be combined with blue bulbs. At the same time, they provide the entire spectrum of light needed by plants. Not so long ago, full-spectrum fluorescent lamps appeared on the market. T-5 bulbs are also available, which emit three times more light than T-8 or T-12 bulbs while consuming the same amount of energy.
High Intensity (HID) lamps
This type of bulb is used to illuminate a large growing area. HID bulbs provide high output with light from a ballast, which allows them to be hung high above plants. These bulbs emit heat that can burn the plant's leaves if they are too close. The hanging height of an HID bulb is determined by its wattage. A reflective hood is often used with these lamps to direct light to the plants.
The HID lamp is used in the greenhouse.
There are two types of HID lights: metal halide and high pressure sodium. Metal halide lighting produces a spectrum of blue light that is very similar to natural light, so it works well as primary lighting. High pressure sodium lights use the red light spectrum and can be used as supplemental light for plant growth. The latter bulbs help plants grow straight and healthy. This prevents unwanted plant distortion and branching. High-pressure sodium bulbs last longer than metal halide bulbs, but should be replaced in accordance with manufacturers' recommendations for maximum efficiency. A bulb that has been used for a long time, but is still working, may emit less light than expected and increase energy costs.
LED grow lights
These bulbs provide a balance between blue and red light. They are small in size and weigh much less than other types of grow lights. LEDs are characterized by high light intensity. They generate almost no heat, so they are very economical in terms of energy consumption.
LED lamps are intended for lighting plants in a greenhouse.
Although they have a higher initial cost, especially compared to T-5 fluorescent lights, they can last an average of 50,000 to 100,000 hours. This is not the best and cheapest option.
Tips to keep your greenhouse energy consumption low
Ventilating and heating greenhouses can be expensive in the long run, especially if you live in colder regions. To be more efficient and economical, you can use these tips and reduce your energy consumption to a minimum.• Keep the greenhouse structure tight by reducing or completely eliminating cracks through which air can penetrate. Seal door frames and other gaps with sealant. Repair all holes in the foundation, doors, greenhouse covering and around vents. Keep the door closed.
• Insulate the greenhouse. If you are building a new greenhouse, add 2 to 5 centimeters of polyurethane or polystyrene insulation over the new foundation. Place the insulating material at a depth of 45-60 centimeters, under the entire foundation. If you already have a greenhouse with a foundation that is not insulated, repair all cracks and holes • Add a windbreak to the outside of the north greenhouse wall. Planting conifers or using a temporary fence as a windbreak can help direct the wind over the greenhouse as well.
• To prevent heat loss at night, place a thermal blanket or night curtain.
• Perform annual maintenance of heating systems (if installed).
• Use HAF fans to circulate air. Keep in mind that a tighter greenhouse retains not only heat but also moisture better. HAF fans improve greenhouse temperature and humidity levels. We discuss greenhouse ventilation in more detail in thisin the article
• Maximize the heated area of the greenhouse and group plants according to their temperature requirements.
• Use infrared (IR) and anti-condensation films to reduce infrared and thermal radiation losses in polyethylene-covered greenhouses.
• Use computerized control systems to increase energy efficiency.
• Use alternative heating sources.