There are a variety of reasons as to why outdoor cultivators use greenhouses to grow their favorite crops, most of which are related to privacy and climate control.

In fact, with more options for climate control within greenhouses, many experienced growers feel that they produce higher-quality products than with traditional summer outdoor grows.

Nonetheless, as anyone who has grown crops in these structures knows, greenhouses greatly intensify the ambient temperature of the outdoors.

Without proper cooling measures, the excessive heat in the summer months can greatly hinder the well-being of a healthy garden. Thankfully, there are a variety of options that greenhouse gardeners can use to help cool their operations during the scorching summer months.

Non-Permanent Structures: Basic Airflow Principles

For those cultivators on a strict budget, or those who just want to grow a small summer crop in the safety of a greenhouse, there are a few tricks that can be done to counteract heat issues. Again, these tips are best suited for simple, non-permanent structures such as hoop-houses.

For starters, cultivators can design their greenhouse foundations with basic permaculture principles in mind, namely digging the base three feet down into the ground. The ambient temperature within the strata of the earth ranges from between 60-70˚F.

Also, summer gardeners can greatly reduce heat issues by simply folding up the walls and removing the ends of greenhouses. This practice leads to a far greater amount of airflow throughout the structure.

To aid in this simple process, and in a fashion akin to indoor growing, an inline outtake exhaust fan should be mounted at one of the highest points of the greenhouse interior, with a length of ducting going to the outside of the greenhouse.

With this set-up, the outtake fan will help remove hot and humid air at the top of the structure. To aid in the interior airflow of the greenhouse, cultivators should also use wall fans mounted directly on the greenhouse frame or T-posts.

It is important to note that when using these passive, slightly-automated cooling measures, gardeners should always use a tall greenhouse frame so there is sufficient space between the garden canopy and the greenhouse roof. This is largely because the very top of the greenhouse has the hottest ambient temperatures as well as the poorest airflow.

Permanent Structures: Wet Walls

For those outdoor gardeners with ample financial resources and large-scale ambitions, permanent greenhouse structures provide the necessary platform for complex, automated cooling systems. Permanent greenhouse structures are generally built on solid, level foundations of concrete or gravel and have the infrastructural might to support heavy equipment additions.

With these notions in mind, all greenhouses fall within two categories—closed greenhouse systems and open greenhouse systems—that directly dictate the choice of an industrial air conditioner or a wet-wall for cooling options.

Both wet wall systems and AC systems are attractive to summer greenhouse cultivators because each approach requires that greenhouse walls stay closed. As a result, privacy remains intact and atmospheric regulation is left largely at the hands of automation and cultivator needs. However, industrial AC systems are extremely expensive and generally only utilized on a commercial scale.

Greenhouse wet wall systems, on the other hand, are semi-affordable, energy-efficient options for those planning a summer garden operation in a permanent structure. While the installation of a properly working wet wall system should be left to a professional contractor, here’s an overview of how it works.

At one end of the rectangular greenhouse, there’s a thick, permeable cooling panel. This wall-sized panel features a pipe on the upper portion that keeps a continuous flow of water going throughout the membrane. When the water finally drains at the bottom of the membrane, it is recirculated to the top.

At the opposite end of the greenhouse, there are large exhaust fans that pull air through the entire length of the structure. The air being pulled through the wet wall membrane and through the greenhouse reduces ambient temperatures inside from 10 to 15 degrees.

One should note, however, that the use of a wet wall system greatly increases humidity within a greenhouse. Therefore, it is essential that an industrial dehumidifier compliments the wet wall system to counteract potential problems with mildew and mold.

Also, wall fans are an essential ingredient in keeping an even environmental stasis through the wet wall cooled greenhouse.

So, no matter what type of greenhouse you have, there are options out there to help keep it cool and safe for your plants in the high heat of summer.