Glass greenhouses

Several types of glazing materials are used by the greenhouse industry. Glass is the traditional one. It’s an excellent material if you can afford the initial outlay as it has a life of at least twenty-five years (some greenhouses on brick frames still have their original glass after fifty years!) and has low maintenance requirements which often don’t get factored into the cost. Of course, glass also transmits light well as long as high quality grades are used for greenhouse glazing.

Glass, of course, needs a frame to hold it, and this can be constructed of a range of materials. Aluminium frames are long lasting, corrosion resistant, lightweight, and can be prefabricated but they cost quite a bit as a capital outlay and you may find you need to have your greenhouse built by a professional. Galvanized steel frames offer high strength and long life at less expense than aluminium frames, although maintenance costs are usually higher. Metals are good conductors of heat, and the heat loss through such a frame can be a significant factor in the long term cost of the greenhouse. Alternatively, wood frames have a low initial cost, but higher maintenance costs. Wooden frames are flammable, and need to be treated to inhibit the risks of decay which is going to be increased by the heat and humidity of the greenhouse.

Glass requires shading to control the intensity of light and lower interior temperatures – the simplest kind is liquid shading (various forms of whitewash and other paint are available) which block the sun's rays. The problem here is that once they are applied, their shading density is not easily changed, and they usually have to be washed off in autumn. Fabric shading can also be used to screen out unwanted amounts of radiation and these shades can be coupled with devices to provide movable curtains offering control of the greenhouse temperature.