Greenhouses are many times more energy-efficient for cannabis production than indoor grow warehouses, and can provide precise environmental control, according to Lindsey Schiller, co-founder of Ceres, a greenhouse solutions provider. Essential to control is a light deprivation system, which allows growers to control the photoperiod, allowing for the 12/12 cycle required by flowering cannabis crops.
A recent article written by Schiller on Ceres’ website suggests five things cannabis growers should look for in a light deprivation system.
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. 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 such as smart controllers monitor many variables. For example, 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.
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.
2. Complete Blackout
If a light deprivation system is installed correctly, a cannabis greenhouse should achieve more than 99% light reduction, meaning almost complete darkness. 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). The ‘pinhole effect’ can be easily countered by using a fabric with multiple layers.
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 works directly with the light deprivation manufacturer.
3. Correct Install
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. Choose 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.
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. 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.
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 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.
For more information, check out the complete article from Ceres.