Best Green Houses

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 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 recognized 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 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.