Greenhouses are generally made of glass for better transparency. However the introduction of plastics has revolutionized the greenhouse industry due to low prices and easier workability. There are wide range of plastic sheets based on sizes, transparencies, strengthens, longevity cost, availability etc. for cladding purpose. Glass is very costly and difficult to work. Several different types of cladding materials have been developed as under:
- Virus net
Conventionally greenhouses were built using glass in steel frames. Glass workability is difficult and needs skilled manpower for cutting & fixing the glass panels. Transparency of the material is good with appropriate resistance and life span. Glass is costly compared with others materials and therefore it is rarely preferred. The glass panels can last for up to 30 years. Transparency remains good if it is cleaned frequently. It is fragile and easily breakable against blows. Moisture from inside may stick to its inner and reduce transparency.
It is an especially treated glass with many times greater endurance against breakage. It is very clear and can be easily cleaned for maintenance for its transparency. It is preferred for greenhouses as it can afford large variation of temperature.
Fiber glass is a very rigid greenhouse cover material. It is available in many layers, in corrugated and flat designs. It can be easily washed with detergents and the dust can be removed from its top surface by simple washing. It is available both in rolls and rigid panels. They are good insulators and helps energy conservation in the greenhouses. It can be easily tightened and persist long life. It is quite light in weight. For very large commercial installations, it can be constructed near to the installation site using skilled work force.
Polythene is commercially available in several grades, types, strengths and transparencies. It is most popular greenhouse material. It is available in countless grades in the market. It is the cheapest of all the materials.
It can be used as a cladding material in the walls of greenhouses to facilitate natural ventilation. If virus net is used in combination with polythene at the roof-top or in the walls, it gives them considerable strength without effecting the transparency. Mostly virus net is used on the outer side whereas, the polythene is used on the inner side of the wall. In this situation the polythene can be rolled up for natural ventilation. When virus net is used on the outer side of the greenhouse, it provides a considerable strength and protects against wind storms.