Greenhouse Construction

Land Selection Considerations Location Topography Future potential Uses Average Climate Labor Supply Accessibility Water Orientation

Location A parcel of land that allows for future expansion Stopping a business growth cycle and having to look for another property can take a toll on a business where building on existing space allows for consolidation and a single location for your business reducing costs.

Land Topography Slopes are a huge consideration with automation and efficiency The same energy it takes to walk up hill has to be repeated for all stages of greenhouse operation by both staff and equipment when building on a sloped area. Slopes also lend themselves to challenges with temperature fluxuations, many separate microclimates, and sun exposure considerations exist on a slope.

Future Land Uses Local Zoning issues need to be investigated and any potential future changes should be understood. Pressures on Southern California land uses have pushed many growers farther away from costal locations and into peripheral areas. Analyzing surrounding trends becomes critical in making any long term plans

Average Climate Understanding the yearly shifts and potential frost days and extreme temperatures allows for preparation with construction decisions and material selection Some materials, building types and glazing options stand up to temperature variations better than others. Understanding the weather changes over a 12 month period and the proximity to the ocean and high wind zones are important in the planning and property selection process.

Labor Supply Is there labor within close proximity to your area or are you isolated? As with most Horticultural activities greenhouse work is labor intensive Often being close to urban areas helps to insure a labor supply In Southern California many nurseries have moved away from urban areas because of the rising real estate costs near the coast

Accessibility to Transportation How close to the nearest freeways or other transportation corridors. Access for trucks and other vehicles on the property, turn arounds parking etc. Layout of the property and the buildings including greenhouses for pickup and staging for easily loading for pickups and deliveries

Water Access to water and knowing the water quality and cost of that water is important. Well water can challenge a greenhouse owner due to many excess minerals that have to be filtered prior to mixing chemicals or fertilizers. pH of the water must also be considered whenever growing specific crops. pH is directly tied to ability of plants to absorb certain nutrients successfully and may need to be adjusted.

Orientation Typically in our part of the Northern Hemisphere Greenhouses are run North and South for the most uniform solar radiation of the leaves of the greenhouse crops. Optimal orientation although extremely important is sometimes trumped by extreme limitations of the site or your existing property

Floor Plan Planning as with any construction project is essential. Knowing the material being grown, the container sizes, standard flat sizes, staff numbers anticipated in the greenhouse will determine bench sizes and aisle ways. Budget will determine construction choices.

Greenhouse Types Lean to: Hobby House Quonset Bow construction Truss Construction Gutter Connected Retractable Roof / Bow / Quonset

Lean to Greenhouse / Hobby House Typically a homeowner or hobbyists level greenhouse Relies on one exterior wall to provides a heat sink for later radiant heat Limited space and controls are usually manual such as louvers , shade or watering systems

Quonset Quonset hut construction comes from WWII military “easy to build” construction techniques relying on series of hoops tied together One of the most common greenhouses for Southern California because of simple construction demands requiring limited heavy materials. Often covered with polyethylene sheets (1 or 2 layers) Challenges with the curve of the hoops reducing workable area (head room) next to the side wall due to the curves shape. Hoops are often mounted on a stem wall to reduce this workspace problem. Would not work in a temperate climate with things like snow load to contend with.

Bow House The bow house introduces taller side walls and often some form of trussing in the roof configuration Allowing for more working space close to the side walls the bow house has slightly more complicated shape and is often a more permanent design. The trussing in the roof is required by the span across the side walls. This trussing sometimes provide a place to hang hanging basket products increasing the overall growing area of the greenhouse wil more plant material. Side walls are often made out of a rigid material such as FRP (Fiberglass reinforced plastic) and the covering is often polyethelene.

Truss (Gable) “Truss” referring to the strong roofing span configuration and “gable” the peaked roof shape The peaked roof would be valuable for accepting and shedding snow loads in more temperate climates The roof Trussing also allows for hanging material and potential increased growing area Most glazing on this design is rigid in nature along with the more complicated truss roof design making them more permanent but costly

Gutter Connected (Ridge and Furrow) Future easy expansion options and an open interior An extreme economy of space with this design Which is often used to grow plant material easily on the ground having lots of flexibility for plant placement. Or with raised benches which would be more permanent, or a combination. With fewer exterior walls widely spaced interior posts help support the greenhouse roof Vehicle accessibility is more realistic with the increased square footage. Used by larger growers and allows for future growth of your operation

Retractable Roof Greenhouse Mechanization adjusts to daily fluxuations in Temperature quickly allowing heat to escape A passive design in that air isn’t forced around by large fans but moves naturally as hot air rises. The opening and closing of roof panels must me automated when in a larger scale operation to reduce labor costs. This mechanization obviously makes for increased cost in the building of the greenhouse and would need to be repairable in a timely way if a crop were in the house when something went wrong.

Glazing Glazing refers to any translucent covering of the greenhouse Glass Fiberglass or FRP (Fiberglass reinforced plastic) Polyethylene Polycarbonate Acrylic

Considerations with Glazing Light transmission (1 or 2 layers) Durability Insulative properties (1 or 2 layers) Replacement cycle Flexibility Dangers

Light Transmission Glass (double-strength float, 3.2mm) 1 88 2 77 Based on Photosynthetically Active Radiation (PAR) values # of Layers % light transmission Glass (double-strength float, 3.2mm) 1 88 2 77 Glass (low iron, 3.2mm) 1 90-92 2 81-85 FRP. Fiberglass reinforced plastic 1 88 Polyethylene (plastic rolls) 1 87 2 77 Acrylic panels 2 83 Poly carbonate panels 2 79

General Characteristics Glass – Heavy, Breakable, long lasting, good light transmission FRP. (Fiberglass reinforced plastic) – Light, Strong, potential yellowing, flammability Polyethylene – Lightest, most delicate, short lived = replacement labor Acrylics and Polycarbonates – Long lasting, slightly flexible, light weight, expensive, usually comes in dual panel configuration.

Benches and Beds Fixed benches/aisles with aluminum benches Considerations: Type of crop grown will determine the interaction of labor in maintaining that crop and the most efficient height and configuration of the benches. In some cases it isn’t benches at all but a floor system with sufficient drainage and larger containers or raised beds within the greenhouse supporting a itself. Floor systems have the danger of contamination from diseases and that must be part of the consideration. Also the ease of working over a longer period of time for staff should considered.

Flood Floor Systems (Ebb and Flood Systems) rely on a well graded floor surface (often concrete with heat tubes) and proper drainage to quickly drain away excess water. Floor systems have an increased danger of contamination from diseases which must be part of the consideration as well as increased bending over of the staff when working on lower material.

Metal – Aluminum or galvanized steel are often used in both construction and bench building due to the strength and anti corrosive qualities of each. Rolling benches have proven valuable in adding to growing space in the greenhouse by creating temporary isles to accommodate the average staff that will be present and working at any one time.

Bench Systems Reinforced glass on blocks Wooden Benches Fiberglass legs and frame and plastic top