As commercial cannabis production shifts to advanced year-round greenhouses, both growers and the environment stand to benefit. Greenhouses are many times more energy-efficient than indoor grow rooms, and can provide precise environmental control. Essential to control is a light deprivation system, which allows greenhouse growers to control the photoperiod, allowing for the 12/12 cycle required by flowering crops.
Most advanced, hybrid cannabis greenhouses use automated light deprivation systems to precisely control the day length. Some cannabis growers – mainly residential growers or three-season greenhouses — use hand-operated systems. In this case, the curtains are pulled open/closed twice a day. That comes with the obvious drawback that someone must be there to operate them — a less reliable strategy overall. As the industry evolves toward larger hybrid cannabis greenhouses with precise environmental control, automation will continue to be the norm for commercial greenhouses.
Automated systems employ motors and controls to manage the system. Controls use a timer, but can also be integrated with a main controller to operate the system based on temperature or other variables. Smart controllers monitor many variables, operating a system accordingly. For example, say it is a cloudy afternoon in the winter. A control system monitors indoor light levels, and will turn on the supplementary lights accordingly. Based on the time of day, it could also close the greenhouse light deprivation system based on set parameters. If it is morning, you may set the curtains to still be open so the plants can take advantage of the diffuse natural light from outside.
Black-out systems can also be operated based on indoor temperature and seasonal conditions. In this way, the grower has a huge amount of control over the indoor environment and light levels. While automation does add significant cost, the return of many crops in a year allows for a very high ROI and quick payback. For example, in a recent Ceres’ commercial cannabis greenhouse, the light deprivation system added roughly $60,000 to the budget. However, it also enabled the grower to achieve 4-5 harvests each year, each of which generated more income than the original cost of the system. In the end, the investment in a light deprivation system was small compared to the added production it allows.
- Complete Black-out?
If a light deprivation system is installed correctly, a cannabis greenhouse should achieve over 99% light reduction, meaning almost complete darkness. Wadsworth Controls, for instance, compared their two layer and three layer black-out fabrics and found the first achieved 99.93% reduction in light. The 3-layer fabric achieved a 99.98% reduction. While that difference may seem trivial to a non-grower, the effect of this 1% of light is hotly debated amongst cannabis greenhouse growers. Some rightfully realize that cannabis has evolved to grow outside, under moonlight, which can be as bright as a greenhouse with 99% darkness. Others feel even these trace amounts of light can disrupt the plant’s 12/12 cycle and turn crops hermaphroditic or stress them.
While horticulturists continue to study cannabis’ required darkness levels, it’s important to consider what you can do to ensure your system reduces light as much as possible. Light leakage comes from two sources: pinhole size gaps in the fabric, and cracks at the edges (where the system should seal to the greenhouse frame). In our experience designing commercial cannabis greenhouses, we find the latter is much more significant. The ‘pinhole effect’ can be easily countered by using a fabric with multiple layers, as demonstrated by the Wadsworth study. Pinholes have a very small effect on indoor light.
Far more challenging is light leakage that occurs around the edges of the greenhouse frame. This occurs when a light deprivation system is poorly installed or designed and does not fit tightly to the frame. To avoid this, ensure that your greenhouse designer / builder knows what light deprivation system you are using. It’s helpful if the greenhouse company designs and sources the system, or liaises directly with the light deprivation manufacturer. At Ceres, we go one step further, working with manufacturers to create a custom light deprivation system designed specifically for Ceres hybrid cannabis greenhouses. That way, we can ensure a tight fit wherever the curtains close at the frame and provide one of the best blackout combinations available.
- Correct Install!
As mentioned above, the design and installation of the system determines its effectiveness at blocking light. If growing in a year round cannabis greenhouse, light deprivation systems are not an area to skimp. We recommend choosing a manufacturer with many years in the business, and one that also offers environmental controls. It is also helpful to use a greenhouse designer that specializes in commercial cannabis greenhouses, and knows how to tailor a greenhouse design to easily integrate with a light deprivation system. Residential cannabis greenhouses or smaller operations have more flexibility, as they have less cash on the line.
Most light deprivation systems easily close over the greenhouse roof. Things get trickier when you consider the sidewalls of the greenhouse, which are often irregularly shaped due to the slope of the structure. Customizing a blackout system to fit perfectly over the sidewalls is challenging, and thus these areas are the most prone to light leakage. For that reason, at Ceres Greenhouses we take another approach: using opaque, insulated metal panels on the east and west sides of the greenhouse. Metal insulated panels significantly reduce the cost of integrating a blackout system. Moreover, they provide highly insulated and durable metal walls. That in turn creates a super energy-efficient greenhouse that can grow cannabis year round even in harsh winter climates. Due to the passive solar design of the structure, and automated supplementary lighting, crops still receive optimal light levels without traditional glazed sidewalls.
Whether growing in a hoop house or year-round greenhouse, sidewalls can be the weak link in an otherwise effective light deprivation system. Consider them early on in your custom greenhouse design and when selecting your system. Ask your greenhouse designer how they plan to accommodate the sidewalls of the greenhouse.
As discussed above, blackout fabrics vary primarily in their light-blocking effect. Other considerations are durability and energy-efficiency. Using aluminized fabrics for heat retention is common strategy in the commercial greenhouse industry – often referred to as thermal curtains. A University of Wisconsin study found that a year round commercial greenhouse with thermal curtains has an average of 60% lower energy costs. In a commercial cannabis greenhouse, light deprivation systems can double up as a thermal curtain, providing both light deprivation and energy savings.
Blackout fabrics can make a greenhouse more energy-efficient by integrating a layer of aluminized fabric, which reflects infrared radiation (heat). On hot summer days, the light deprivation fabrics reflect heat away from the greenhouse, reducing heat gain and the need for cooling. On cold nights the curtains trap heat inside the greenhouse, reducing the need for heating.
When selecting a system, ask manufacturers about additional energy-efficiency of a fabric. At Ceres, our standard fabric is a three-layer blackout fabric: the bottom two are standard black out layers, and the top is an aluminized heat-reflecting cloth.
For assistance in creating a cannabis greenhouse with a custom light deprivation, please contact Ceres for more information or a quote.
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