1 minute read
Deciding on the Cover of a Greenhouse
The question of what the ideal greenhouse plastic is to cover a greenhouse often surfaces. On the market, there are many types of greenhouse plastic from which to choose. The main decision relies with the available budget, understanding the local environmental conditions and the production objectives before investing in an important component of the production system.
Polyethylene
Advertisement
During the early 1960’s, 6 mm polyethylene sheeting came on the scene for hoop house style greenhouses. Then and even today its greatest asset is its price, as 6 mm plastic is economical. Since 1970 technology on greenhouse covering increased and then UV inhibitors were added to give the plastic a longer lifespan. It was clear that, although 6 mm plastic could survive the sun for up to 3 years, a longer lifespan was needed to decrease input costs to the system. But, half a century later 6 mm poly is still used by some budget conscious growers. This film lasts according to the manufacturers’ specifications, but growers do stretch the limits to avoid costs – many times to their own peril. The downside to 6 mm is poor weather (excessive wind, or hail), and our South African sun. A bad storm may damage the cover and recovering might be necessary. Over and above, crops may be damaged or lost in a strom. Thus, the 6 mm polyethylene covering will last potentially for four years and pay the farmer the cost of its purchase, but one must take into account the labour and time to recover every 3-4 years or possibly sooner in case of loss through adverse conditions.
Polycarbonate
Polycarbonate for walls is an extruded polymer product. This is impact resistant and offers thermally insulation. It is attractive, will not yellow and is fairly easy to install. The down side is how easily damaged it can get from wind, storms, and severe hail. It could attract
when recovering a greenhouse, the labour cost and production downtime must be brought into consideration; and therefor also perfectly managed to resume production as early as possible.
