Why Choose polythene or plastic film clad greenhouses

WHY CHOOSE POLYTHENE OR PLASTIC FILM CLAD GREENHOUSES?

In a world of rapidly changing markets, pressures of ever increasing competition, trends in health and safety, and speed of technological change, the case for plastic clad greenhouses has never been stronger.

A commercial polytunnel greenhouse purchased today from Clovis Lande is as reliable as a glass clad structure. The cost of replacement plastic cladding every 5 years compares favourably with the maintenance cost of glass.

Development of innovative claddings never stops. Plastics are available which incorporate additives which selectively block or enhance certain wavelengths, improve growth rates, inhibit certain diseases, and enable correspondingly reduced use of chemicals. Since plastic cladding has to be changed every 4 to 5 years, it is easy to keep up with technical advances. Conversely, there are inbuilt problems of cost for users of glass.

Existing high investment entry costs for glass structures will increase still further if gantry systems, advocated by the Health & Safety Executive, have to be installed for glass cleaning.

Plastic (Polythene) films for Greenhouses
Clovis Lande stock the Industry Standard tunnel cladding films from BPI Agri (formerly Visqueen), although there are many makes of polythene on the market. We only use Visqueen films as they have been developed and tested for years before being released on to the market.

All the Visqueen range of horticultural films are manufactured using CO-extrusion technology to bond together three separate layers of polyethylene to produce a much tougher film and to control surface properties and radiation transmission. The durability of Visqueen film has been understood and appreciated by growers for many years.

Films Comparison : Typical Properties

	Light Transmission	Light Diffusion	Thermic Effect	Thickness Microns	Yield Strength	Fold Impact
Clear UVI/EVA	90%	20%	55%	180	8 MPa	>550g
Politherm AF	90%	22%	82%	180	7.5 MPa	>550g
Luminance THB	87%	>90%	88%	180	7 MPa	>550g
Luminance THB AF	87%	>90%	90%	200	7 MPa	>550g
White UVI/EVA	67%	>90%	55%	180	8 MPa	>550g

CLEAR UVI/EVA
A clear film which is resilient and easy to install. An economical choice for applications where there is little to be saved on heat inputs and where condensation is not a problem.

POLITHERM AF
Has thermic properties to improve heat retention and additives to control the condensation of water on the film. Temperatures will be higher and savings can be made on overnight heating. If properly installed, water will condense uniformly on the film rather than as droplets. This improves light transmission and reduces the risk of water falling on plants. Best for crops which respond well to high direct light levels and warm temperatures.

LUMINANCE THB
Combines high diffusion, high light transmission and excellent thermic properties. Designed to make more light available to plants by increasing the amount of diffused light to close to the maximum, and to reduce the proportion of short wavelength infrared light. Can achieve good growth rates with reduced risk of scorching. Particularly effective for ornamental plants and for nursery stock, and has been shown to give improved yields of tomatoes. The thermic properties will help to maintain overnight temperatures.
Note, however, that spring growth may be earlier under Politherm.

LUMINANCE THB AF
Adds condensation control properties described above in to Luminance THB.

WHITE TINT UVI/EVA
Reduces overall light transmission by about 20% compared to clear, for cool greenhouses where reduced growth rates are required or tolerated. Cuts down light evenly across the PAR spectrum so that plant growth is not distorted. Traditionally used for holding nursery stock, and the best choice for plants such as ferns and conifers which are at the most risk of scorching.