From Quonset huts to high-end glass houses, cannabis growers have an array of structure options to accommodate their unique needs
By Karli Petrovic
Selecting the perfect structure for your grow operation is easier said than done. Although cannabis tends to be low maintenance compared to some other agricultural products, growing impeccable plants requires the right house. There are an abundance of available options, but growers shouldn’t be intimidated. In this guide, manufacturers reveal the pros, cons, costs and other relevant information about different styles of greenhouses prevalent in the cannabis industry.
Glass/polycarbonate commercial greenhouses
When envisioning a tradition greenhouse, most people think about the glass or polycarbonate structures that house everything from petunias to basil to cannabis. Commercial growers have been using these options for decades. And as an increasing amount of industry professionals expand into the marijuana market, it’s likely these structures will remain popular.
The main difference between the glass and polycarbonate options is light diffusion, or the ability for sunlight to be distributed throughout the structure instead of beating down directly onto the crops. Glass houses require adjustments to diffuse light, but polycarbonate houses are designed to diffuse light from the get-go.
According to Jonathan Valdman of Forever Flowering Greenhouses, glass structures were designed for very northern and very southern climates where the amount of light coming into the greenhouse is minimal. “It’s an older method of creating greenhouses,” he says.
Once a hallmark of the commercial agriculture industry, the glass house is slowly falling out of favor. Because glass is not conducive to light diffusion, the sunlight entering the greenhouse can burn the plants. “A glass house is going to be too intense for cannabis,” Valdman says, noting that people who have glass houses often use shade curtains to help diffuse or scatter the light. “When people talk to a greenhouse manufacturer who isn’t familiar with cannabis, they end up creating all these hurdles and then trying to find solutions.”
Another thing to consider when selecting a poly house is whether gutter-connecting the structures is important. Not all models will allow growers the option to have connected structures. At Forever Flowering, for example, the taller Original Gardener (OG) line of framed structures can be gutter-connected, but the Northern Latitude line of gothic-framed houses can’t.
One important thing the two lines have in common are ridge and side vents to facilitate passive cooling. Valdman says this feature is essential because it eliminates the need for cooling systems, many of which require electricity. By reducing the leaf and root temperatures through passive cooling, growers prevent plants from transpiring and reap the savings of reduced water and nutrient inputs.
Cost: The starting price ranges based on size and quality. Northern Latitude series starts at $3,000 with the OG series starting at 20-25% more.
Size: Varies based on needs and whether a grower wants gutter-connected houses or individual structures
Pros: Better control over the environment; durability; effectively diffuses light; year-round growing
Cons: Expensive, difficulty to construct
Level of environmental control: High
Growing type: Depending on the height of the structure, plant height may be limited. That said, growers can use blackout cloth (several companies sell light deprivation systems that can be included in the greenhouse package) to produce cannabis whichever methods work best for each grower. For those who want to do many cycles per year, multiple houses are preferable so plants in the vegetative state live in one structure while those flowering or finishing are in another
Quonset structures
A common structure for storage or growing vegetables, the Quonset hut can be a versatile option for cannabis growers. SteelMaster Buildings, a company that specializes in arch steel buildings, recently sold nine Quonset structures to a cannabis grower in Washington who used them for everything from a pump house and secure storage area to an indoor growing facility. Based on their needs and application, growers can work with the manufacturer to determine the structure’s size and durability.
With respect to the individual applications, however, the Quonset excels in the areas of indoor growing and secure storage. As SteelMaster’s Scott Buckman points out, “Unlike a greenhouse, you can control the amount of light that gets in. There’s a wide opening in the front and back but it can be shut so there’s complete darkness.”
While this means growers will need to use supplemental light and pay for higher electrical costs, it also eliminates the need for shade or blackout cloths to protect the plants from harmful UVB rays, says SteelMaster’s William Swafford. “Growers can completely control the environment within these structures,” he continues, noting that a buttoned-up Quonset house is a cleaner alternative that’s “almost bulletproof” against pests.
It also happens to be resistant to another type of pest: namely, thieves.
“One of the biggest pros is that if you don’t have 24-hour guards, the structure is more secure than most other greenhouses,” Swafford says. “Cutting through one of these is a lot louder and more difficult.”
Cost: The starting price ranges based on quality, but the price of materials ranges from $7-$15 per square foot. Growers will also need to pay for foundation materials (concrete, etc.), utilities like plumbing and electricity, and labor to construct the building if they don’t have the skills to do it themselves.
Size: Varies based on needs, but the typical width is 30-50 feet and spans as long as growers want.
Pros: Economical, easy to construct, secure, built-in light deprivation, durable in relatively extreme weather conditions, good pest management.
Cons: Lack of natural light requires electricity and other costs associated with environmental controls.
Level of environmental control: Medium
Growing Type: Any growing method can be achieved in this structure.
High tunnels and hoop houses
Though the terms are often used interchangeably, the high tunnel and hoop house are slightly different. A high tunnel has a single layer of polyethylene, and a hoop house has a double layer of the film plastic, which provides added protection and insulation. Both are generally used as a temporary structure or season extender, not for year-round growing. Additionally, these structures are typically unheated and provide an economical alternative to growers who don’t want to invest in — or can’t afford — a traditional commercial greenhouse.
According to Brooke Edmunds, a Ph.D. at Colorado State University Extension and author of the presentation “Greenhouses for Small Farms,” those who opt for a high tunnel or hoop house have two design choices: the half-circle Quonset style and the bowed gothic style. Both options can be bought as kits and assembled by hand. While the Quonset style is often cheaper, it doesn’t have a high tolerance for extreme weather or snow stress. For growers in milder climates, such as California, the design is an ideal choice. Gothic designs, on the other hand, boast opposite characteristics. They’re slightly more expensive but shed snow with greater ease.
In addition to snow load and other weather conditions such as wind gusts and hours of sunlight and shade, growers should consider a few other factors before selecting one of these structures. For one, Edmunds indicates that site preparation and proper drainage are essential. Depending on how the grower intends to use the house, she also suggests building the structure near utilities like electricity (for running fans or cooling systems) and irrigation water.
Many outdoor growers also use open-air hoop houses in conjunction with blackout cloths for shorter season light deprivation crops.
Cost: The starting price ranges based on quality. Materials can cost less than a dollar per square foot on the low end with a quality hoop house starting in the $1,200 range.
Size: Varies based on needs
Pros: Economical, easy to construct
Cons: Lacks durability, not effective in all climates, requires blackout cloth to achieve light deprivation, pest control can be an issue
Level of Environmental Control: Low
Growing Type: Typically a season extender, but in mild climates, it can be used year-round. Sans blackout cloth, this structure is often used for finishing cannabis plants rather than in a vegetative or flowering stages.