Greenhouse Structure – How It Has Changed Over The Years
By Abhishek Agarwal
The construction of greenhouses has been revolutionized by the advent of modern plastics. A range of possibilities are available that would have been unknown in the past.
Greenhouses were once made of wood and glass and even cast iron and glass. These materials represented a dramatic technological development in their time. Now these traditional materials are a rarity. They are preserved in the grounds of stately homes and classic botanical gardens.
The arrival of aluminum made greenhouses available to a wider market after World War Two. They were still glazed with glass and comparatively expensive. But the demand for the hobby greenhouse had begun.
While high quality hobby greenhouses are often made of quality timber such as redwood the most common type of greenhouse structure for the amateur is made of aluminum. A timber frame will always look better. The aesthetics of the aluminum structure reveal its origins in commercial horticulture. To many people they are unappealing, if functional.
Commercial greenhouses are still often based on aluminum structures, but the glazing material has changed. Greenhouses are usually glazed with twin wall polycarbonate these days. This material has the advantage that is is cheaper than glass and does not shatter. It also provides better thermal insulation than glass. The air trapped between the two walls keeps warmth from escaping into the outside environment.
Even the frame of a greenhouse may be made of plastic. The potential of UPVC, a rigid plastic material that is resistant to ultraviolet radiation, was first recognised in the construction industry. It is employed for doors and double glazed windows. The same system has now spread to greenhouses. Standard units of double glazing, or made to measure panels, are made in a factory and brought to the site where they can be bolted together.
The use of new materials has allowed new designs of greenhouse structure to be explored. A greenhouse used to be a rectangular structure often with a pitched roof. This was a practical design and is still widely used. But the dome shaped greenhouse has become increasingly popular. Often called a solar dome, this type of structure makes the most use of light.
Dome shaped greenhouses were constructed out of cast iron in the nineteenth century. They were a great luxury. They were often used as palm houses. Surviving examples are spectacular and rare structures.
Aluminum allowed dome shaped greenhouse to be mass produced for the first time. The same shape can now be found in redwood frames too. Greenhouses of this type are often used as sun rooms and to cover pools in cold climates.
On a vast scale the same concept of a dome shape has been for the famous Eden Project biomes in Britain. The framework of these structures is made of steel. Three giant dome shaped greenhouses cover a reclaimed china clay pit and provide a series of environments that reflect the diversity of the planet.
No less visually spectacular, in its own way, is the humble polytunnel. This is a greenhouse structure made of a plastic sheeting stretched over a steel framework. Greenhouses of this type are widely used commercially. There are so many of them in Southern Spain that they can be seen from space. Satellite pictures show large areas of the region carpeted with polytunnels.
Their commercial uses are obvious but they the polytunnel can also be used in the same way as the more spectacular greenhouses of the Eden Project. The Alternative Technology Centre in Wales has a polytunnel planted with a range of tropical plants. A small water feature provides humidity for the plants. The whole
effect is of a peaceful and lush tropical environment.
At a simpler level the use of plastics has created the possibility of a greater range of temporary structures than was possible in the past. It is possible to build. or buy ready made, a vast range of temporary plastic greenhouses that will fit into the smallest space. Even people who have only a balcony or terrace can now have a greenhouse.
Now that the greenhouse is no longer confined to the simpler rectangular structure it is possible to adapt them all types of space. Modern plastic materials can be cut, bent and stretched in ways that would have been impossible with glass. The change in greenhouse structure and the availability of new materials has made the greenhouse more accessible than ever before.
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Related Resources
Horticulture Web – Your source for Greenhouse and Horticulture …
HorticultureWeb.net was created to assist greenhouse growers, nursery growers & others in the horticulture industry by providing a centralized place to …
www.horticultureweb.net/
Solar Greenhouse Resources
Greenhouse glazing. In: K.V. Garzoli (ed.) Energy Conservation and Solar Energy Utilization in Horticultural Engineering. Acta horticulturae. Volume 257. p. …
attra.ncat.org/attra-pub/solar-gh.html
Horticulture Greenhouse Facilities | Department of Horticulture
Adjacent to the Department of Horticulture in Tyson building is our 26000 ft2 teaching and research greenhouse complex, managed by two full-time and several …
horticulture.psu.edu/node/492
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