Building a cannabis greenhouse is a major investment. Overall cost approx. $8,000,000 depending on the greenhouse size, type of environmental equipment, and geographic location. Additional factors include: growing climate, production goals, and the overall capital budget. Making the best decisions possible during the planning process will substantially increase the probability for long-term success once the greenhouse is in cannabis production.An area with a substantial impact on the financial cost structure is the system of environmental equipment and controls. Taking the time to understand the local weather patterns and necessary cultivation methods to effectively grow crops in a specific geographic environment is crucial to cost-effective cannabis greenhouse operations. With this knowledge in place, the best environmental equipment decisions can be made.
As a greenhouse manufacturer, Nexus designs high quality, commercial greenhouses for the traditional horticulture and the emerging cannabis markets. The company partners with environmental equipment and control providers, and manages the development of integrated greenhouses. This outlines the various options for optimal greenhouse cultivation.The main purpose of a greenhouse heating system is to replace energy lost when outside temperatures are below the desired greenhouse temperatures. This lost heat is based upon four factors: Surface area, Geographic location, Type of crops, Heat loss rate.
One common method is overhead forced air unit heaters, which run from hot water, natural gas, propane, or oil. These heaters blow hot air into the cannabis greenhouse to maintain environmental air temperature set points. This effort ensures the entire plant canopy receives an equal amount of heat. In addition to providing ideal temperatures for good plant growth and yield, the heaters contribute to dehumidification in combination with controlled venting.
Unit heaters are very popular due to the low capital and insulation costs, high reliability and the ease of staging multiple heaters.
Horizontal air flow, working in combination with overhead heaters, horizontal airflow fans provide a consistent distribution of carbon dioxide, humidity, and temperature especially during the winter months. Horizontal air movement is created by the strategic placement of HAF fans at a height of approximately eight feet from the floor or above the plant canopy. The fans also ensure that cold air brought in by ventilation systems mix uniformly with the warm air inside the cannabis greenhouse. Fans are located along the length of the greenhouse. The direction of air flow alternates among adjacent growing areas. Each fan should be placed approximately 50 ft. apart inside the growing space or at intervals of 25% of the total length. For cannabis, there can be up to one-third more fans than in traditional growing. With continuous air movement, these fans significantly improve the plant microclimate and overall plant quality
Heating plant root zones with overhead heating is often challenging since pushing heat to the floor area can be difficult (heat naturally rises). One solution to this concern is floor or benching systems with radiant heat. Floor heating consists of plastic pipes embedded into concrete or sand beneath the floor surface. Warm water flows through the pipes and emits heat into the floor areas. This heat covers multiple growing zones with uniform temperatures. However, floor heat cannot be used to warm air temperatures without raising root temperatures to excessively high levels. Benching heat systems involve water pipes above the floor and under the bench systems. The heat pipes are closer to the growing containers and provide the shortest route of heat flow to reach the soil. For most crops, soil temperature is more important than air temperature.
Root zone cannabis heating benefits include better germination of seed, faster rooting of cuttings, and increased plant growth and disease control in potted plants. Regardless of the type of root zone heating system, the greenhouse needs to have a boiler system to heat water to the 120-200 degree F temperature level depending on the type of boiler.
Cooling and ventilation is important all-year long and not just in the summer months. Heat stress can occur even on days when outside temperatures are 30 degrees or more below the desired inside temperature. On a clear day of 60 degrees, the temperatures inside a greenhouse can exceed 100 degrees. Without proper ventilation, greenhouses can easily become hot enough to damage cannabis crops.
By replacing the warm, moist air inside with cooler, dry air from outside, then the growing environment becomes better suited for cultivation. In additional to cooling the cannabis greenhouse, ventilation reduces the internal humidity levels and replenishes the carbon dioxide that plants consume during photosynthesis.
Ventilation occurs from either natural or mechanical systems.
Natural ventilation, this type of ventilation is driven by temperature differences inside and outside the cannabis greenhouse or wind conditions that create small air pressure differences. Vents are opened to get the warm air to leave and cooler air to enter. The specific type of natural ventilation method used is largely dependent upon the geographic location. Naturally occurring wind breeze along with proper greenhouse orientation can be an especially effective combination in some geographic areas. Understanding the meteorological environmental in specific geographies is crucial to designing natural ventilation systems.
Evaporative cooling reducing air temperature by evaporating water into the air is a common method of greenhouse cooling. As water evaporates, heat energy is lost to the air, which reduces the temperature. A fan and pad system is the preferred evaporative cooling method for many greenhouse cannabis growers. Exhaust fans are placed in one end wall and pads on the opposite end wall. Water consistently moves over and through the pad while operating. The fans exhaust air from the greenhouse and pull fresh air in through the moist pads. The air loses heat and the temperature drops. This drop in temperature depends on the air’s capacity to absorb water. Evaporative cooling is more effective when humidity in the outside air is low. When the outside air temperature is 95 degrees with 50 percent relative humidity, the drop in cooling is approximately 13 degrees. Yet, if the relative humidity is 70 percent, then the expected cooling would be 8 degrees. If the relative humidity rises to 90 percent, then only a 2 degree temperature drop is likely to occur. Due to solar radiation, the air will gradually heat up from pad wall to the exhaust fans.
Positive pressure cooling high volume jet-fans pull air through an evaporative cooling system and push this air into the cannabis greenhouse with special convection tubes. This process increases static pressure inside the greenhouse. Ridge vents maintain normal pressure inside, which allows the heat to escape. Another benefit of a positive pressure system is insect exclusion. When positive air flow from inside the greenhouse reaches the roof vents, then the pressure substantially reduces insect entry. Adding insect screening to the roof vents increases the potential for nearly full insect exclusion even more. The need for pesticide use will decrease.
High pressure fog systems are another greenhouse cooling method, which can be a supplemental alternative to other systems. Fog nozzles are placed all through the greenhouse as well as at the air inlet. Water evaporates throughout the greenhouse instead of only along one wall with a wet pad system. These systems can be expensive due to the large number of necessary nozzles and high pressure pumps required to make small water droplets. Good water treatment and filtration is essential to produce actual fog rather than mist. Consistent maintenance is important to prevent chemical and biological buildup in the nozzles. A benefit of a fog system over a pad wall is a more uniform temperature from inlet to exhaust.
Humidity, a secondary role of a ventilation system is to reduce or eliminate excessive humidity. When there is not adequate ventilation, extra humidity condenses on leaf surfaces, which increase disease potential.
Condensation contributes to deterioration of the greenhouse components. Light transmission is reduced as well. When the moist air around the cannabis is replaced with the cooler and drier outside air, then internal humidity levels substantially fall. Consistent equipment operation, reasonable plant spacing, and early daily watering are best practices for reducing relative humidity and preventing cannabis plant diseases.
Ventilation and airflow proper ventilation and sufficient airflow are vital to managing relative humidity inside a greenhouse. Warm air has a higher capacity for moisture than cool air. On a warm, sunny day, the air within a greenhouse accumulates moisture. As evening approaches, outside temperatures cool, the internal air temperatures drop, which reduces the water-holding capacity until water condenses on the plant and greenhouse surfaces at the dew point.
To reduce this type of condensation, air exchanges will remove the moisture-filled greenhouse air and replace it with drier, outside air. If the new air is cool, the fresh air needs to be heated to reduce internal relative humidity levels. Horizontal airflow blends cool and warm air together within a cannabis greenhouse to buffer the air from falling below the dew point. To reduce this type of condensation, air exchanges will remove the moisture-filled greenhouse air and replace it with drier, outside air. If the new air is cool, the fresh air needs to be heated to reduce internal relative humidity levels. Horizontal airflow blends cool and warm air together within a cannabis greenhouse to buffer the air from falling below the dew point.
Insect exclusion since cannabis is a consumer product, a minimal number of pesticides are available for commercial use. Using an insect screen is a common method for reducing pests. While screening does not guarantee a complete pest-free greenhouse, it makes a major difference. Screens create resistance, which limits the ability of the pest to enter the greenhouse. Appropriately matching the mesh type to the pests you are trying to exclude is important. Another method is positive pressure cooling. Air is pushed through an evaporative cooling system, which forces the air into the greenhouse. Exhaust vents must be designed to allow air pressure to stabilize while still creating higher air pressure inside the greenhouse than outside. Due to this internal air pressure, insect infiltration through greenhouse openings is further restricted
CO2, enriching cannabis with additional CO2 is an option to increase plant growth and crop yields. The ideal quantity depends upon the type of cannabis, light intensity, temperature, and crop growth stage. Many growers do not monitor CO2 levels. As long as crop yields are sufficient, growers may be satisfied with the overall production effort. However, monitoring can occur with infrared CO2 gas monitors at a reasonable cost. If these monitors show that CO2 levels are insufficient for expected cannabis yields, then a CO2 enrichment system can be implemented.
There are many ways to enrich CO2 levels. A natural approach can be initially considered. Approximately, one to two hours after sunrise, CO2 build-up from the night is at a high level. Horizontal airflow improvements can be made to distribute CO2 evenly throughout the greenhouse. An optimal CO2 level is 1,000 to 1,200 ppm.
If natural CO2 enrichment does not achieve the desired results, then other options may be considered. When outside air conditions are too extreme for proper ventilation, then extra CO2 from liquid or bottled CO2 gas may be needed. Careful handling processes are implementation from these sources. In addition, specialized equipment, which are designed and certified for CO2 application, is another option.
Fertigation maintaining adequate plant nutrition is one of the most important factors in cultivating greenhouse cannabis. Most growers utilize a liquid feed program as their main method of supplying plant nutrients. The frequency of these liquid applications can vary with some growers supplying the nutrients at the peak periods of vegetative or reproductive growth. However, a constant feed (soluble fertilizer at each irrigation) is often the preferred method for producing the best plant growth.
By injecting soluble fertilizers into the irrigation system, the following benefits can be obtained, Precise control of nutrient concentration and supplemental minerals, Customization of nutrient solutions to fit the requirements of any plant stage or species, When properly applied, there is a low potential for over- fertilization or crop salt injury, Fertilization solutions are easy to monitor and apply to crops.
Fertigation provides an accurate and consistent application of nutrients to the wetted plant area, where the active roots exist. This effort is a highly efficient process since the plant roots absorb the nutrients, which increases plant growth and reduces wasted fertilizer. However, fertilizer recommendations aren’t available due to a lack of federal regulations.
Environmental controls cannabis greenhouse environments have unique challenges for effective environmental control. Temperature fluxuations may occur rapidly and widely vary depending on solar radiation levels, ambient temperatures, humidity, wind velocity and direction, amount of plant material inside the greenhouse, and watering practices. Proper control of the cannabis greenhouse environment is challenging, yet the benefits of good control far exceed the costs.
The overall objective of any greenhouse system is to reduce the input cost per unit of production and maintain or increase the quality of production. While some enhancements improve the input cost and/or functions of a few specific tasks, such as heating or cooling, an integrated environment system will have a positive impact on nearly every greenhouse component. Even an incremental performance improvement in several areas will lead to much better overall results.
According to the National Greenhouse Manufacturers Association, specific benefits include, Higher Energy Efficiency, better equipment coordination and more accurate control can reduce heating, fuel, and electrical costs, Better Labor Efficiency. automated controls increase the productivity of workers by, enabling them to focus on more essential tasks, Improved Management Effectiveness, Additional information is available to managers and growers to help them make better management decisions and spend more time managing the operation, Reduced Water Use, growers report reduced overall water use of up to 70% with the most effective irrigation controls, Reduced Fertilizer Use, when combined with lower water use, fertilizer application and improved efficiency can occur, Reduced Chemical Use, more precise control of temperatures and effective use of growth regulating temperature practices, which reduces the need for growth regulators, Reduced Pesticide Use, greenhouses with better climate control and precise irrigation produce healthier plants, Improved Plant Quality & Uniformity, less disease, more effective irrigation and fertilization, improved grower information, and management all combine to increase the health and uniformity of plants, Reduced Equipment Wear & Tear, continuous monitoring and alarms alert growers to pending breakdowns and other problems prior to more serious consequences, Less Plant Loss from Failures. Good data logging and graphing of greenhouse conditions and sophisticated early warning alarm systems help reduce losses from catastrophic failures. Energy efficiency in a cannabis greenhouse is a result of many varied functions.
Similar to a home, there are extensive maintenance tasks, which if consistently implemented, can significantly reduce energy consumption as well as utility bills. Beyond maintenance, there are design and growing system components that also contribute to lower consumption patterns. When all of these areas are combined, then the cumulative impact can be substantial. With a System 420™ hybrid greenhouse from Nexus, the grower can receive the privacy benefits of the indoor grow and the modern agricultural practices of the greenhouse. Cannabis crop efficiency, reduced operating costs, natural sunlight, and a healthier work atmosphere can be achieved in a hybrid greenhouse growing environment. As a greenhouse manufacturer, Nexus designs high quality, commercial greenhouses for the
traditional horticulture and the emerging cannabis markets. The company partners with supplemental equipment providers, and manages integrated greenhouse development. This outline several items to
consider for increasing cannabis greenhouse energy efficiency. Outside of licensing fees, energy ranks as one of the top expenses for marijuana
cultivators in many states – in some cases hitting $50,000-$60,000 or more a month for large growing operations
Heating energy represents 70% to 80% of a greenhouse grower’s total energy. Consumption, with this level of costs, developing an efficiency plan may determine whether a cannabis company financially survives. The days of easy money in the cannabis industry are nearing a close. Falling prices, oversupply, and rising utility costs are contributing to a tighter financial model. Reducing utility bills are about more than increasing profit. Energy efficiency may determine business survival.
Gutter-connected cannabis greenhouses, which cover one-half of an acre (21,780 sq. ft.) have 10% to 15% less surface area and a lower amount of heat loss than most stand-alone greenhouses, which cover the same area. Stand-alone greenhouses have a surface area-to-floor area ratio of approximately 1.6 and gutter-connected greenhouses have a ratio of less than 1.4. A comparison of two greenhouse systems with 24,000 sq. ft. of floor space brings intriguing results. Each operation features LP gas power-vented unit heaters with a seasonal efficiency of 78%.
Roof and wall coverings a fundamental method for efficient greenhouse heating is to assess the specific structure.
Energy losses vary depending on the greenhouse covering and the structural age. Overall, newer structures will have better seals around the coverings and openings than older houses. Double-layer coverings including acrylic, polycarbonate, and polyethylene transmit light quite well and retain heat better than single-layer glass or single-layer polyethylene. Rigid materials (acrylics and polycarbonates) can be more expensive, yet are often worth the cost due to the durability and energy savings. These double-layer coverings usually use 50% less energy that single-layer coverings.
Polycarbonate structured sheets, either in multi-wall or corrugated configurations, are common in the cannabis market. The multi-wall sheets give the user additional energy savings over single wall polycarbonate, while the single wall covering will have a higher light transmission for the plant. Both types of sheets can be manufactured with light diffusing abilities.
Understanding cannabis crop needs based upon light, heat, humidity and geographic environmental factors will help determine the best covering selections for each greenhouse operation. Insulation in cannabis greenhouse walls, which face north let in a smaller amount of light than the other walls, especially in the winter months. Insulation can be added to the north walls to reduce heat losses. If the walls have a white surface, light levels will be enhanced by reflecting winter sunlight that would have passed through the north wall. Using insulation between the metal side-walls and around heat plumbing provides significant energy savings. The addition of light deprivation or energy shade curtains is one of the most effective ways to conserve energy. This effort can reduce nighttime heat loss by about 50%.
Another cannabis greenhouse area where heat is lost is along the inside perimeter through the greenhouse ground and sidewall portions. Insulated boards that run from the bench height to slightly below the ground level contribute to about a 5% energy savings. Light deprivation curtains also contribute to energy efficiency by retaining heat during the night or blackout hours.
Heating in cannabis greenhouse heating energy efficiency involves the type of heating system, location, and maintenance. Unit heaters are popular in greenhouses due to low capital and installation costs, dependability, and staging ease. Multiple heaters are highly recommended to reduce the potential for total heat loss from equipment failure. In larger greenhouses, a central hot water boiler is a common choice.
Heat is distributed through heated floors, radiant heat pipes, or water-to-air heat exchangers. An efficient boiler with consistent maintenance will keep energy costs at reasonable levels.
A productive heat distribution location can lower energy consumption while increasing plant growth and yields. Cannabis greenhouses frequently use one or two forced-air unit heaters that distribute air above the plant height level. When two unit heaters are used, then placement usually occurs in opposite corners on opposite ends of the greenhouse to create circular airflow.
Heaters are often placed at elevated heights to allow more room for benching systems. Since heat rises, the entire greenhouse must be heated to maintain the desired temperature at the crop level. Distributing heat from the floor, under benches, or bench-tops creates a growing climate that warms the plants and adjacent areas, yet does not heat up the entire greenhouse. Known as root zone heating, this cannabis crop production method provides additional energy savings.
Horizontal air flow (HAF) fans, reducing air leaks and heat loss makes a cannabis greenhouse tighter. Regardless of the heating system type used, placing a sufficient number of HAF fans to adequately circulate air inside the greenhouse will increase energy efficiency. Solid air circulation will improve greenhouse temperature and humidity consistency, which reduces the number of cold pockets and improves plant quality and uniformity. Keeping the humidity level below 80% by venting, when necessary, minimizes disease incidence.
Air circulation by the HAF fans should consist of two to three cu. ft. per min. over the greenhouse floor surface. A 28-ft. x 96-ft. greenhouse needs an airflow of 5,376 cu. ft. per min.
(28 x 96 x 2 cu. ft. per min. per sq. ft. = 5,376 cu. ft. per min.). This cannabis greenhouse structure would require four HAF fans with a capacity of circulating air at 1,440 cu. ft. per min. HAF fans usually operate at two different speeds. Be sure to check the fan specifications to determine the necessary speed. These fans should be situated two to three feet above the plant. Height level and aligned parallel to the greenhouse sidewalls so that air can flow in a circular pattern. Winter operation is recommended to improve temperature and humidity levels. The use of supplemental lighting allows the cannabis grower to accomplish the following, Provide extra light on cloudy and low natural light days (winter, northern latitudes), Different growing environments require a varied amount of accumulated light, Maintain consistent light levels during the year. These types are high pressure sodium and metal halide fixtures. To decrease energy consumption, timers or light integral controls can be used. These types of controller measure the sunlight that enters the greenhouse on a daily basis and regulates the lights to ensure ample light reaches a minimum daily light integral, which determines plant growth.
The greatest benefit of a cannabis greenhouse is the energy saved by using the free light of the sun. Greenhouses are covered by light transmitting coverings, which allow in 80% to 90% of the available sunlight. The differences in light transmission are due to the variety of coverings used on the greenhouse roof and sidewalls. These coverings reduce the necessary amount of artificial and supplemental lighting that decrease overall energy consumption. Light deprivation is a technique of altering the light cycle of flowering plants. These systems utilize the power of natural sunlight, an abundant source of free energy. Cannabis greenhouses use blackout curtains to block light and deny the crop an extended photoperiod.
A light deprivation system inside a cannabis greenhouse can reduce heating costs by at least 50%. The use of sunlight decreases the role of artificial lighting, which is a large part of the utility cost structure. As a result, greenhouses have increased overall energy efficiency.
According to curtain manufacturer Nexus, the utility costs within a greenhouse are 50-75% lower than in an indoor warehouse growing environment.
The blackout curtains underneath the roof coverings and along the sidewalls help retain heat during the dark periods. Heat is retained in the growing area without losing heat energy through the roof. This process needs to be carefully managed to prevent extreme heat buildup, which can damage plants.
There are many greenhouse environmental factors that need to be managed, especially air temperature, humidity, CO2 levels, lighting, and irrigation. To better control energy costs, several interactions need to be avoided. These interactions include running exhaust fans when the heater is on, cycling heaters and fans on and off, and operating fans while adding CO2.
With manual controls, some interactions cannot be avoided. However, with a central controller, the control system can be optimized to prevent unnecessary conflicts.
A basic controller usually manages heaters and fans to permit the heater to have day and night set points. If the greenhouse fans are staged, a basic controller may also increase the number of operating fans as
internal greenhouse temperatures rise. Sophisticated controllers may have outputs to control heaters, fans, louvers, CO2 enrichment lights, thermal or shade curtains, or irrigation, as well as inputs for temperatures, humidity, CO2 levels, daily light integrals, soil moisture, and a weather station. Proper measurement methods are vital to obtaining accurate temperature readings.
Whether using a mechanical thermostat or a sophisticated computer system, a regular tune-up is essential. An inspection by an environmental controls company with specialized knowledge may be necessary.
However, any greenhouse manager can perform basic checks. For example, if the ventilation fans are running while the heat is on, then there is a concern.
In conclusion, when building and developing a cannabis grow operation, preparing a business model is crucial to financial viability. Achieving significant profit levels can be challenging due to an increasingly competitive
environment with turbulent price changes and rising costs. By focusing on our financial model, which emphasizes a strong revenue growth, cost management, and optimum efficiency, the grow operation can generate substantial profit and avoid the downside consequences of tightening economics in the cannabis industry.