Basics
Very generally speaking, there are three basic types of greenhouses suitable for commercial use:
- Quonset greenhouses are the most common type of free-standing greenhouse for commercial production. Based on designs used by the US military in WWII, Quonset huts are designed to be lightweight, easy to ship, and assembled without skilled labor.
- Gothic arch greenhouses take the basic semicircular roof of a Quonset greenhouse and add a small peak at the top rather than a smooth curve.
- Gable roofs or A-frames are the quintessential peaked roofs formed when two slanting sides form an angle where they meet - pretty much the roof design for all children’s drawings.
- Gutter Connected: These greenhouses (also called ridge and furrow) are set side-by-side and connected at the eaves by a common gutter. Below the gutter there are usually no internal walls which permits generous space and flexibility. These connected greenhouses may have either gabled or curved arches, and several gutter connected greenhouses in a row are often referred to as a “range”
Free Standing Types
Free-standing greenhouses are often the best choice for small growers who plan on less than 10,000 sq ft of growing space because they offer a lot of flexibility such as separate growing environments in each house. Individual greenhouses can also be shut down when not in use, but it’s also easy to build additional greenhouses as more space is needed. Free standing greenhouses allow more flexibility for non-level sites and they’re less expensive to build as site preparation and erection costs are less.
Free Standing Quonset Style:
- Quonset style greenhouses are typically the cheapest and easiest to construct and can be built up to 34’ wide and any length.
- Quonset style greenhouses can be constructed low to the ground using PVC pipes to act as simple cold frames or as tall high tunnel greenhouses using aluminum components according to the climate and demands of the plants you’re growing. Glazing for this type is typically flexible films that easily conform to the semicircular structure. Because the walls curve all the way to the ground, there is limited room against the sidewalls for either storage or plants, though it is possible to set a Quonset on columns to give taller plants room to grow.
- Largely because of the simple construction of Quonset or hoop style houses, they are typically operated on more passive principals than other greenhouse types and generally do not have electricity. There is almost no internal structure to support motorized vents, complex irrigation systems or even exhaust fans, for example, so temperature control in Quonsets may simply involve rolling up end and side walls to allow heat to escape on warm days.
Free Standing Gothic Arch Style:
- Arch style roofs offer good light transmission and can use either rigid or flexible glazing materials. Their structural components are simpler than gable roof buildings, typically using only curved bows and purlins. This type of greenhouse is also more efficient than the Quonset style, since more headroom and growing space is available at the sidewalls.
- The point at the top of a gothic arch helps shed snow and ice more effectively than a Quonset or hoop style arch.
- The simple structure of an arch style design makes it easier and cheaper to build, but it also reduces the number of internal structures which could be used to hang baskets or support irrigation booms.
Free Standing Gable Roof Style:
- Gable roof style greenhouses use traditional welded or bolted trusses to support the roof. These are more expensive and complex to build, but they do provide plenty of internal strength to support curtain systems, boom irrigation, automated basket systems, and other equipment.
- The use of trusses allows gable style buildings to span widths up to 60’.
- Fewer problems with dripping condensation, better angles for capturing winter light, and greater flexibility with venting options, including retractable or open roof systems (below) make gable roof greenhouses an attractive style in demanding climates and situations where even a gothic arch style greenhouse won’t perform well.
Gutter-Connected Greenhouses
Connected greenhouses can be based on gable or arched-roof structures that are connected at the gutter level. Interior walls are usually eliminated, and the individual bays may vary from 12’ to 30’ wide and overhead clearance is typically 10’ or more. Multiple bays can be connected to reach the desired width, and bays can be as long as desired.
Gutter-connected greenhouses offer the most flexibility of all greenhouse designs. Tall sidewalls allow full use of the horizontal space and ample headroom permits easy air circulation as well as room for equipment trusses and screening systems.
Gutter connected greenhouses are ideal for setups of 10,000 sq ft and more, where economies of size for heating, centralized utilities, and automation systems quickly come into play. Since they’re a single structure, they occupy smaller footprints per usable space. On the downside, ridge and furrow styles are much more vulnerable to snow and ice accumulation in the eaves.
Retractable Roof or Open Roof Greenhouses:
Generally designed either as a flat or gable roof style, retractable roofs offer great flexibility for providing both natural and highly controlled environments within the same structure. They can be configured as basic crop protection from heavy rains and easily reconfigured as a complete artificial production system with retractable curtains for shading, heat retention, or insect screening. These options permit growers to open the structure partially or completely, allowing partial or complete ventilation and light exposure. These are typically used with ridge and furrow style greenhouses, and offer a natural environment when weather is good or an artificially protected environment when it’s called for, without the need to constantly move plants from place to place.
