Articles
DIRECT AND DIFFUSE LIGHT TRANSMISSION OF INSECT-PROOF SCREENS AND PLASTIC FILMS FOR CLADDING GREENHOUSES
Article number
559_29
Pages
203 – 210
Language
English
Abstract
Optical properties of several greenhouse-cladding materials were evaluated using direct and diffuse light transmission laboratory equipment.
Samples of two insect-proof screens of different porosity, four low density polyethylene (PE) films and one co-extruded three-layer film were evaluated.
The effect of ageing on direct light transmission of some of the tested materials was also measured.
Main results can be summarised as follows:
Samples of two insect-proof screens of different porosity, four low density polyethylene (PE) films and one co-extruded three-layer film were evaluated.
The effect of ageing on direct light transmission of some of the tested materials was also measured.
Main results can be summarised as follows:
- The capability of insect-proof screens to transmit light was very good and comparable to that of the three-layer films.
Light transmission is a function of the porosity of the screen; the bigger porosity the better light transmission.
- Three-layer film and 0.1 mm PE non-thermal films transmitted more light than the other plastic films.
Maximum light transmission for these materials was close to 90 %.
- Light transmission of thermal PE films is clearly less than that of three-layer films.
For instance, maximum direct light transmission of one of the thermal PE samples was only 83 %. This loss in light is expected to cause a reduction in yield and quality of winter crops in Mediterranean areas.
- Film ageing under exposure to field conditions contributed to a loss in light of 5 % approximately.
- For all tested materials, diffuse light transmission was lower than direct transmission at zero incidence angles.
Diffuse light transmission ranged from 81 % for the most porous screen to 65 % for one of the thermal PE samples.
Authors
J.I. Montero, A. Antón, J. Hernández, N. Castilla
Keywords
Optical properties, ageing, dirt, dust, thermal polyethylene, three-layer film
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