3 Signs you Should Invest in a Sealed Cannabis Greenhouse

By Haley Bridgnell
sealed grow room design

3 Signs you Should Invest in a Sealed Cannabis Greenhouse

3 Signs you Should Invest in a Sealed Cannabis Greenhouse

Cannabis growers today face a huge range of options for growing structures. Traditionally, there are outdoor grows, indoor grow rooms with lights, and year round cannabis greenhouses. More recently, the cannabis greenhouse industry has expanded to include more options ranging from simple hoop houses to advanced hybrid year round greenhouses with insulated side walls, often called hybrid structures. Today, some cannabis growers are going a step further, limiting the air exchange and creating an almost sealed environment inside. “Sealed” cannabis greenhouses — sometimes called enclosed cannabis greenhouses — are an emerging trend because they provide greater environmental control, reducing the risk of pests and ameliorating the challenge of odors. At Ceres, our sealed greenhouse for cannabis solution is called the SunChamber™ and we will be talking more about its benefits and capabilities as we go along. 


What is a Sealed Cannabis Greenhouse?

Traditional greenhouses are normally heavily ventilated during the day to prevent overheating. A standard rule of thumb in the commercial greenhouse industry is to exchange the entire volume of air in the greenhouse every minute. That requires enormous fans to constantly flush air outside. In a cannabis greenhouse, this results in continually venting warm, CO2 rich, and odorous air outside. In turn, ventilation raises a number of issues. In many areas, regulations prohibit exhausting untreated, odorous air outside. Furthermore, excessive ventilation can bring pests and pathogens into the greenhouse.

sealed grow room designSealed greenhouses aim to solve these issues by keeping treated air inside. Instead of ventilation, they use advanced and innovative climate control systems to provide cooling, air circulation and climate control. For instance, The Ceres SunChamber™ relies on the EcoLoop™, a geothermal HVAC system, to heat, cool and dehumidify the sealed environment in order to maintain precise growing conditions for the plants without ventilation. Furthermore, sealed cannabis greenhouses are often slightly pressurized inside to prevent outside air from wafting in when doors are open.

To learn more about our geothermal climate control system for sealed greenhouses, please read our blog, “Introducing the EcoLoop™: Ceres’ Most Energy-Efficient Heating and Cooling System Yet”.

A strategy in themselves, sealed cannabis greenhouses have a number of pros and cons, and important ramifications on the cannabis sealed grow room design. (Note, that while we say “sealed” greenhouses, no environment is ever completely air tight. Sealed cannabis greenhouses are typically equipped with back-up ventilation. Some air exchange occurs, though it is dramatically lower than ventilated versions.)


Advantages of Sealed Greenhouses for Cannabis:

Odor Control

In many municipalities, regulations prohibit cannabis greenhouses from exhausting untreated air outside due to the odor. While there are a few ways to control odors of traditional cannabis greenhouses, enclosing the greenhouse and circulating air inside is often much cheaper and more effective. They reduce the reliance on cumbersome carbon filters (which need to be replaced every few months). 

Pest Control

Sealed greenhouses for cannabis reduce biological contaminants (pests and foreign diseases) entering the greenhouse. Monitoring for pests is still a forefront issue; if a pest population gets in, it has a protected environment to thrive. Still, sealed greenhouses reduce pests, making the greenhouse more sanitary and controlled overall.

No Cross-Pollination

Nationwide, a new biological contaminant has emerged: hemp pollen. If there is an outdoor hemp grow nearby, air-born pollen will easily enter a ventilated greenhouse and pollinate a cannabis crop, causing plants to go to seed. Seeded cannabis is still sellable, but is no longer marketable as a product direct to the consumer. Here in Colorado, cannabis growers have reported seeded cannabis plants losing over half their value. By enclosing a greenhouse, a grower reduces the chance of exposure to hemp pollen, making the operation more financially secure.

Energy Efficiency:

Standard commercial greenhouses are very ‘leaky’ and inefficient structures. Typically, energy for heating and cooling is the 2nd or 3rd largest expense in a commercial greenhouse, second only to labor costs. By limiting the openings in the structure and utilizing a hybrid cannabis greenhouse design, sealed greenhouses for cannabis are tighter, more insulated structures. In turn, they are cheaper to heat and cool when the greenhouse must be conditioned. 

Hybrid greenhouses combine standard glazing and insulated side-walls, creating an insulated greenhouse that can grow much more easily year-round. Particularly in winter, sealed greenhouses are incredibly efficient at holding in heat. (Check out Ceres video of a sealed cannabis greenhouse in Boulder, CO, which grows year-round with minimal heating costs). Not to mention, if a geothermal HVAC system, like the Ceres EcoLoop™, is added to the mix, growers can save even more on energy costs. 

CO2 Conservation:

Most cannabis growers supplement CO2 to increase yields. In a ventilated greenhouse, much of the added CO2 is exhausted outside during the day, essentially wasting it. Sealed cannabis greenhouses are able to maintain higher CO2 levels more efficiently and cost-effectively because they retain the conditioned air inside.

Higher Yields and Higher Quality of Product

Increased biosecurity and complete climate control means that growers can expect higher yields and higher quality of product. We’ve seen growers operating in our Ceres SunChamber™ receive 50% more per pound of flower than the average market value due to the high quality of their end product. In addition, growers can expect yields of ~60 grams per square foot of canopy space per harvest of dried flower.

sealed grow room design

Disadvantages of a Sealed Cannabis Greenhouse

Excess Humidity 

All greenhouses are prone to high humidity, due to the water vapor that evaporates from leaves during photosynthesis. In an enclosed greenhouse this water vapor gets trapped inside, making it prone to excessive humidity, and increasing the risk of molds and diseases. To accommodate, sealed greenhouses for cannabis must use a sealed grow room dehumidifier, such as Ceres EcoLoop™ or standard dehumidifiers. Additionally, the greenhouse must be equipped with sufficient air circulation. With these methods a sealed cannabis greenhouse can maintain the ideal relative humidity levels of 40-60%.

Risk of Overheating

Without venting, sealed cannabis greenhouses require advanced cooling systems, such as a Ceres EcoLoop™, evaporative coolers or hydronic cooling systems. Many of these systems require less energy input than your traditional chiller-based cooler, creating a year round sealed cannabis greenhouse with lower operational costs. Still, the risk of overheating the structure needs to be planned for and carefully monitored with greenhouse control systems. With help from Ceres’ Smart Controller, the SunSense™, growers can closely monitor their greenhouse conditions in order to continually optimize their environment.


Though sealed greenhouses offer greater control, they normally require more advanced climate control systems to handle overheating, dehumidification and air circulation. The upfront investment in an automated and controlled cannabis greenhouse is normally higher than ventilated versions. The good news is these systems require less energy input, making the greenhouse more energy-efficient overall and the payback relatively quick.

So, is a sealed cannabis greenhouse the right fit for your grow? 

This decision comes down to your location and priorities. A sealed grow room design is likely your best investment if:

  • The greenhouse is in an urban area

Cannabis greenhouses in urban areas are subject to tighter regulations regarding odors. A sealed greenhouse is much easier to operate due to cost-effective odor control in tightly regulated zones.

  • There are outdoor hemp grows in the area

If the greenhouse is near an outdoor hemp grow – which is a more common problem since hemp is federally legal  — hemp can easily pollinate a cannabis greenhouse crop. A sealed greenhouse for cannabis provides a much higher level of crop protection, justifying tighter control.

  • You want a highly controlled environment

Though you must mitigate excess heat and humidity, sealed cannabis greenhouses offer greater environmental control. They reduce the biological contaminants and dust entering the greenhouse. Advanced climate control systems precisely regulate temperatures, CO2 and air circulation, without relying on ventilation.

Bottom line, it’s more beneficial for your grow to go with a sealed greenhouse if you can afford the upfront cost because the downsides are outweighed by all the values that a sealed structure provides. 

At Ceres, we design custom energy-efficient cannabis greenhouses with a whole system approach to suit growers’ needs. This means we do all the structural, mechanical, and electrical engineering to build a greenhouse from the ground up to work as a whole system so it operates exactly how the grower wants it. We apply this type of approach to both our sealed and ventilated greenhouse solutions. We also take into consideration growers’ climates and local building codes, in order to provide the best, most cost-effective greenhouse for every grower.

For more information, or to get a commercial greenhouse quote, contact us today.

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