GLAZING OPTIONS

For many years the only option available for the amateur greenhouse gardener has been horticultural glass. Whilst it is suitable for growing, it is the lowest grade of glass produced and it has the disadvantage of when broken it  produces dangerous dagger like shards that can cause serious injury. Now other greenhouse options are available as follows. 

TOUGHENED SAFETY GLASS
Many greenhouse manufacturers now supply tempered safety glass, either as standard or as an option. Its main benefit is that it is harder to break but if it does, it will do so safely into very small fragments, similar to the side windows of modern cars. Toughened glass offered by some manufacturers is 3mm thick and the best use 4mm thick.

ADVICE
If you have children or frequent elderly visitors or other peoples children you should consider toughened glass, which has an impact strength of up to 5 times greater than that of ordinary glass of the same thickness. It is however very important to ensure that the toughened glass you are supplied is to the British Standard BS6206 Grade A

CLEAR ACRYLIC

A few manufacturers of cheap greenhouses supply glazing in 2mm or 3mm Acrylic glazing throughout and the curved eaves designed greenhouses use this material for the curve. 

ADVICE  
Not the most practical material for glazing greenhouses for two reasons. Acrylic normally has a short life and does get very brittle. However the the major reason it is Acrylic creates an abundance of static which draws dust to both surfaces and in turn very much reduces valuable light entering the greenhouse, particully in the Spring season.

POLYCARBONATE
This tough, twin walled material is shatterproof and is offered generally in 4mm or 6mm thick for greenhouses. The additional benefit of Polycarbonate is that it has excellent insulating properties which is ideal if you intend to heat your greenhouse during the winter and spring months.

ADVICE
This material is unfortunately very expensive. Beware that some cheaper greenhouses are offered with only 4mm thick Polycarbonate which will make a flimsier greenhouse even more flimsy. Whilst having good insulation properties, unfortunately Polycarbonate can act in the reverse in summer months making it difficult for you to keep temperatures down.  I advise that this form of glazing should only be considered for the better quality framed greenhouse. It is also important to ensure that the Polycarbonate offered has a Long Life outside surface treatment. Otherwise it will discolour by turning yellow and become brittle in only a few years.