Glasshouse, Plastic Greenhouse or Shade Net? Choosing for African Conditions

The choice of a growing structure should follow the crop, climate and commercial plan. Glasshouses, plastic greenhouses and shade net structures provide different degrees of protection and control, with different costs and operating requirements.

Start by defining the conditions the crop needs and the period in which it must produce. A structure that works well for seasonal production may be unsuitable for a contract requiring consistent deliveries through the hottest or wettest months.

Describe the actual design

The covering material tells you only part of the story. Two plastic greenhouses can differ substantially in height, ventilation, structural strength and installed equipment. Glasshouses also vary in specification. Shade structures range from simple covers to more extensive protective installations.

A meaningful comparison should include dimensions, covering properties, openings, screens, cultivation systems and climate equipment. The FAO's greenhouse production guide examines design and covering materials as connected choices, including the effect of insect screens on ventilation.

Ask suppliers to price against the same production requirements. Otherwise, the comparison may place a simple shelter beside a fully equipped growing facility and treat the difference as the price of glass.

Define the protection you need

Write down the constraints that the structure must address. These may include excessive radiation, rainfall on the crop, wind, low temperatures or pest exposure. Then assess the proposed design against each requirement.

A shade net structure may suit a crop that benefits from reduced radiation and some weather protection while tolerating substantial contact with the outside environment. It does not provide the same enclosure as a roofed greenhouse. The actual protection depends on the net, construction and site.

A plastic greenhouse offers a roofed production environment with considerable variation in design and control. Evaluate the specified film, ventilation and installed systems, together with the replacement work the covering will require.

A glasshouse can form the basis of an intensive production system with integrated climate and cultivation equipment. Its commercial case depends on whether the intended production and operating life justify the investment. Structural engineering, glass specification, maintenance and local service arrangements all belong in that assessment.

Assess the operating consequences

Consider who will run each option. More equipment creates additional requirements for control settings, inspection, maintenance and fault response. The owner needs a team and a budget capable of meeting those requirements.

Ask how essential components will be serviced. Establish the availability of spare parts and skilled technicians, the consequences of a failure and the time required to restore operation. Include access for cleaning, covering repairs and crop work in the design review.

The greenhouse also needs to fit the rest of the farm. Crop handling, movement of staff and materials, packing and dispatch should be considered before the layout is fixed.

Compare the full commercial cases

Use the same crop and sales assumptions where they are applicable, then explain where a design changes achievable output or the production season. Compare total capital expenditure, operating costs, major replacements and the uncertainty around saleable production.

Avoid assuming that every additional kilogram will earn the same price. The market must be able to absorb the volume and accept its specification. A structure capable of producing more has a stronger investment case only when those additional sales and their costs are credible.

The comparison should answer four questions:

1. Can the design support the required crop and production period?
2. Can the site's water, power and labour resources support its operation?
3. Does the expected commercial result justify the whole-project cost?
4. What evidence could change the choice?

Choose before the project becomes difficult to change

Structure selection affects foundations, services, crop layout and subsequent procurement. Resolve the main alternatives early enough for the result to influence those decisions.

Drylands designs and operates high-tech greenhouse farms, and brings that experience to technical design and feasibility assignments. The assessment begins with the project requirements and the conditions on the proposed site.

If you are comparing structures, discuss the crop, location and commercial brief with our team before requesting a final specification.