Small Garden Green House Design
As far as the framework of your garden green house is concerned your choice is really between wood and aluminum, although a third choice – plastic piping – is currently being developed and may prove cheaper than the others.
Aluminum will not rust or rot, but it is generally agreed that it reacts more strongly to hot and cold than wood and therefore cools the greenhouse in winter; my own belief is that this is not a significant factor. Aluminum looks ugly, is hard to work yourself and is fairly expensive. If you decide on aluminum you have really got to buy your garden green house ready-built.
Wooden garden green houses must be made from a decay-resistant wood like cedar, redwood, 01 cypress. It is pointless using soft wood or any wood that requires constant painting to stop it from rotting. Wood has a tiny disadvantage in that it obscures more light than aluminum, but it looks nicer and you can work it yourself. And a cedar garden green house should last as long as you will.
The choice of transparent sheeting for green houses lies between glass, and three kinds of plastic: fiber reinforced, which is a transparent form of fiber glass; PVC or acrylic modified plastic, which is a fairly stiff plastic; and polyethylene which is flimsy.
Glass lets in a lot of light, looks good, lasts a very long time, is seldom broken by wind and can easily be mended, but it costs a lot and requires a strong framework to carry its weight. Fiber reinforced plastic comes in large sheets; it is easy to fit and does not need extensive framing. It also takes some of the heat out of a hot sun, which is a very good thing. However, it does not admit as much light as glass and this is a serious disadvantage in winter. It is also inflammable, and will only last twenty years.
PVC and acrylic modified plastic are cheaper and transmit light well, but they will last only five years and can be ripped by a gale. Polyethylene is very cheap – about a tenth the cost of glass – and transmits light very efficiently. But it will only last one or two years, and is very easily ripped by gales. Transparent plastics are becoming very popular all over the country, and as long as plastics remain cheap relative to glass, they are well worth using. Glass is, of course, better in the long term, but -it represents a substantial capital investment nowadays.