Multi-Span and Single-Span Polytunnel Installations

Multi-span polytunnel constructions are large-scale connected tunnels designed specifically for professional horticultural and agricultural use, particularly in the mix of produce that can be harvested from single to multiple commercial polytunnels, from vegetables, herbs, fruits, flowers, and nursery plants. Unlike smaller tunnels, commercial polytunnels are often customised to the owner's bespoke requirements to meet the specific needs of the growing operator in size, shape, materials used, crop types, location demands, and climate conditions.

Why Are Multi-Span Polytunnel Constructions Bespoke?

Multi-span polytunnel constructions span and connect across multiple bays under a single continuous structure and are often larger than an aircraft hangar. With efficient and effective coverage of the land, better airflow control, and large-scale mixed cultivation. The large interior can be divided up, and different coverings can be in place to allow for sectioned areas requiring different light and warmth levels. Often, due to varying operator requirements, such as site orientation, wind exposure, snow load, irrigation and heating systems, or crop height and spread. Standard commercial polytunnels in kit form or "off-the-shelf" models are sufficiently effective if not mixing crop types.

Many commercial polytunnels are custom-engineered to optimise specific factors that can include:

1. Size, Height and Shape

2. Intended Crops or Use Purpose

3. Ventilation Options

4. Types of Covering for Light Diffusion and Temperature Control

5. Internal layout for Accessories, Systems, and Manual or Automated Controls

6. Build Durability to the Demands of Local Weather and Locational Conditions

Bespoke commercial polytunnels starting from design, size and build type can be complex and specified to suit individual customers' growing needs, such as: hydroponics, climbing frames, automated shading, growing beds, guttering, water storage, or climate control from solar panels.

Accessories and Features for Polytunnel Constructions

To maximise and raise performance, functionality, and productivity levels, multi-span commercial polytunnels often incorporate additional accessories and design features, from single to multi-span polytunnel constructions:

1. Guttering Systems

Rainwater is harvested through integrated guttering, preventing water pooling and enabling direct flow to storage tanks.

2. Cladding Materials

The outer cladding influences light transmission, insulation, and durability. Options include:

Polythene film UV-stabilised, anti-drip, layered, insulated and diffused options

Polycarbonate sheets are more rigid and robust, twin- or multi-wall choices

3. Door & Roof Openings & Ventilation

Commercial polytunnels often have various ventilation and door options, which can be manual or automated. Roof or ridge vents allow hot air to escape, while side roll-up vents enhance cross-ventilation. Systems can be climate-controlled or integrated with thermostatic sensors to suit various-sized, lengths, widths, heights, and shapes of polytunnel constructions.

4. Tailored Access Doors

Sliding or hinged doors of different materials for manual or automated access for day-to-day care, harvesting, allowing vehicle or machinery access. Double-door entry systems to reduce air exchange

5. Windows & Louvres

Side wall windows or louvres can be fixed or adjustable for fine-tuned air control. These improve airflow and help prevent overheating or disease outbreaks.

Polythene vs Polycarbonate Options

A key decision in polytunnel construction is the choice of thickness and suitability to crops in the covering material used.

Polythene Film Choices For: Easier to install, choices in light transmission and variable insulation levels, value for money

Against: Susceptible to ripping and tears or UV degradation, needs replacing quicker depending on grade and costly if good insulation is required.

For longevity, it must be UV-stabilised with standard gauge covers lasting 4 to 6 years, depending on gauge thickness and weather conditions. Thicker, layered or insulated types last 6 to 8 years.

Cost: Has a lower initial outlay, ideal for large-scale operations, budget-conscious operations and small growers who are placed in protective surroundings

Polycarbonate Sheets

Fors: Highly robust, durable, rigid, has better thermal insulation, fire-resistant and longer longevity.

Against: Heavier structure and stronger fastenings add to the cost, offering lower light transmission.

Longevity, depending on thickness, durability, is from 10 to 15 or 20 years of service with regular maintenance and cleaning.

Cost More: Around 2 to 3 times the outlay of standard polythene, longer time to fit, but more durable and thicker, with options, twin or triple-walled

Final Thoughts

Multi-span polytunnel constructions are modern components of complex commercial polytunnels built for various growing operations and farming needs. Their natural and bespoke nature allows them to be fine-tuned for crop-specific needs and the demands of local climates. Specific configurations will depend on environmental demands, the stress they undergo, budget costs, crop value, operational goals, and production objectives, which collectively determine polytunnel constructions.

Read More:

Common Polytunnel Repairs: From Garden to Commercial Scale

Buying a Polytunnel: What to Look For & Questions to Ask