Right-sizing Your Greenhouse Structure and Systems
August 7, 2025 
Industrial greenhouse with rows of cultivation. | Photo courtesy of Adobe Stock
There are a lot of newbies in the greenhouse business who believe the only way to grow a high-quality crop is by precisely controlling every variable and input, like so many attempted to do in vertical farms.
Nadia Sabeh, Dr. Greenhouse
It’s understandable; operators want to grow a high-quality crop consistently and predictably. They’re looking for solutions that reduce the cost of labor and energy. They want to supply their region with locally grown food that didn’t have to travel 3,000 miles or across borders.
To grow locally means operating in areas that are not necessarily ideal for the crops we want to grow. There’s too much or not enough light. It’s extremely cold in the winter or oppressively hot and humid in the summer. The neighboring farms spray pesticides in the summer and breed botrytis in the fall, both of which can drift into the greenhouse.
So what do we do? We seal them up! We air-condition them. We install electric lighting. We do everything we did indoors and then some to protect our crops and protect our fears of failure.
But is a sealed greenhouse necessary? Do growers really need a high-tech greenhouse to produce a high-quality, highly predictable crop using less labor? Maybe not.
Where to Begin
There are many different greenhouse types and options to choose from: low-tech, high-tech, hybrid, high tunnel. How do you know which is the “right” greenhouse for you? Ultimately, it comes down to two primary factors: crop and climate.
Assuming the crop is known, the greenhouse design and its choice of systems really depends on climate. When reviewing greenhouse quotes and proposed designs, it’s important to consider the following five climate-related attributes.
1. Greenhouse Height
There’s a reason why greenhouses seem to be getting taller and taller: They create a space above the canopy where heat and humidity can escape. Shorter greenhouses tend to trap heat and humidity around the canopy, especially without adequate ventilation or air circulation.
The optimal gutter height will depend on the crop and its canopy height. If you’re growing lettuce or strawberries at bench height (approximately 4 feet above ground), then look for a minimum 14-foot gutter height. If growing a vining crop 8 to 10 feet above ground, then consider an 18- to 20-foot gutter height. There’s one potential downside to a tall greenhouse: There’s more volume of air to heat, ventilate, and condition. But typically, the benefits outweigh these concerns.
2. Glazing and Cover
Glass, polycarbonate, polyethylene, acrylic, ETFE: All these materials have unique properties that affect what happens inside the greenhouse. If you’re in a cold, northern climate, think about investing in higher-cost glass. Glass is opaque to longwave radiation, making it the ideal candidate to reduce heating needs due to the “greenhouse effect.” On the other hand, if you’re located in the Sunbelt, glass can increase your cooling needs, so picking a plastic option—polycarbonate or polyethylene—might be better because plastic is generally transparent to longwave radiation.
Other local factors to consider when choosing a glazing system are hail, earthquakes, and local energy codes.
3. Supplemental Lighting
The need for and use of supplemental lighting is highly dependent on how much natural sunlight is available in the area. Clemson University has a great online tool (available here: https://webgis.coe.clemson.edu/storymaps/light-integral-map/) that shows a U.S. map of the average daily light integral (DLI) for every month of the year. This map can be used to determine how much supplemental lighting is needed in the winter, when sunlight levels are expected to be lowest.
If you’re growing lettuce in the Sunbelt or sunny Colorado, you may not need any supplemental lighting to achieve lettuce’s relatively low target DLI. But if you’re growing strawberries in cloudy Michigan or tomatoes in Portland, you may need a lot of supplemental lighting to hit the crop’s relatively high DLI needs year-round.
4. Shade and Thermal Curtains
Shade screens and thermal curtains are effective at reducing heating and cooling needs. Shade screens reduce the amount of solar heat gain that reaches the canopy. Not only do shade screens reduce cooling demands, they also lower plant heat stress and evapotranspiration rates, two conditions that increase water and nutrient demand and increase the risk for leaf tip burn and blossom end rot.
Thermal curtains reduce heat loss from the greenhouse and are typically used on cold nights. They act like an insulator, trapping heat below to keep the canopy warm. Using a thermal curtain can reduce heating energy needs, which is why some people refer to them as “energy curtains.”
Some manufacturers provide two-in-one curtains, where a single cloth can both shade during the day and insulate at night. If you’re in a sunny and cold climate (like Montana), you may want to look for a curtain that offers both benefits.
5. Heating, Venting, and Cooling (HVAC)
HVAC systems offset the energy losses (heating) and energy gains (cooling) in a greenhouse to achieve target temperature and humidity levels. There are many ways to manage temperature and humidity in a greenhouse, and figuring out which system is best depends greatly on the crop and climate.
Heating systems range from overhead unit heaters to hot water pipes that radiate heat to the plants and greenhouse surfaces. The size and type of heating system will depend on the lowest temperature night of the year, as well as the other decisions you make about glazing and thermal curtains. If you’re in snow country, running heat pipes at the gutter line is recommended to melt snow and prevent a collapsed roof.
Cooling can be accomplished through ventilation, evaporative cooling, and air conditioning. Ventilation and evaporative cooling are most effective in mild climates and where the outside humidity is generally lower than the target inside humidity. These systems are not nearly as effective in hot, humid environments and can exacerbate high humidity challenges. Air conditioning can both cool and dehumidify the greenhouse, but it’s expensive to install and operate.
The type and size of the cooling system depends on choices made around greenhouse glazing and shading. It also depends on how the supplemental lighting will be used. Good airflow from circulation fans and irrigation management also affects HVAC system needs.
Climate is King
When developing a new greenhouse project, there’s a lot to think about: site layout, product flow, automation, and the market you’ll be delivering to. When it comes to the structure itself and the systems you employ, climate plays an oversized role. Knowing local weather patterns, sunlight availability, and even predominant wind directions can help steer you in the right direction when choosing the greenhouse that’s best for you and your crop.
This article is a part of CEAg World’s Industry Report: Greenhouse Produce. Download the full report here: https://stage.ceagworld.com/industry-reports/.