Tom Manning, a project engineer in the Department of Plant Biology and Pathology at Rutgers University, recommends that growers first consider internal improvements and the potential costs before committing to building entirely new structures.
“Typically, once a structure is completed, you don’t change the fundamental structure,” he says. “So, everything is done either on the surface of the structure or the equipment within the structure.”
One such improvement is going from a single glazing to a double glazing if a grower values energy efficiency more than light. That can still be expensive, but not as expensive as building an entire new structure. Additionally, growers using double acrylic glazing or something similar may switch to triple glazing for the same reasons.
“You might decide it’s worth the investment in triple-glazing,” Manning says. “That’s something you have to run the numbers on because the more layers you add, the less incremental savings you get. You have to decide if [the improvements] are actually going to pay for the new glazing.”
However, Manning notes that there are obvious upgrades to make for those considering building a new production space. For instance, a grower working in a hoop house can become more energy efficient by switching to a gutter-connected structure. Specifically, depending on the size of the operation, switching to a gutterconnected system can result in noticeable energy savings. Per Manning’s calculations, moving away from hoop houses on a half-acre scale could result in a 20 percent reduction in energy costs. When expanding to a full acre, savings jump to around 25 or 30 percent.
“It depends on your configuration, what your hoop houses look like and how high you make the greenhouse,” Manning says. “One of the compelling reasons to switch to a gutter connected house can be labor because growers have an easier time [managing] labor in a gutter-connected house than they would in a hoop house.”
If a grower is considering building a whole new structure, many of the same factors — most notably cost — still apply. He also notes that it’s important to understand what any upgrades would change about the overall growing environment.
“One thing people always ask is ‘Does it make sense to keep the greenhouse lower in order to reduce energy losses through the walls?’” Manning says. “Typically, the response it will save a little on energy, but it will compromise your growing operation. Particularly in larger greenhouses, the contribution of the walls to the overall energy losses is relatively small.”