Screens offer some of the greatest benefits available in glasshouses today by enabling you to control the growing environment.
There are two types of screens, each named according to its function. Thermal screens regulate internal heat and light, and insect screens keep pests out. Usually they are used separately, but sometimes they will be used together, in research stations for example.
They are available in a variety of materials, and so there is no “correct” one to use. The one that is best for you will depend on whether you want to use it inside or outside of your glasshouse, as well as the amount of heat and / or light that your plants need to receive.
Some plants want full sun, others dappled shade and others want to always be fully in the shade.
Not all screens are merely translucent. Some are breathable as well and allow not only air, but light rain to pass through them.
The poor man’s version of screens is paint. The problem with painting the glass is that you lose control over the amount of heat and light that is transmitted into the greenhouse. That’s because it isn’t cost effective to put it on one day and then to take it off the next; and when the shorter days arrive, you have to have it removed anyway in order to take advantage of the little of daylight that is available.
With screens, you can do that, or at least what amounts to it. When the sun is strong, the shading can be increased. When it’s cloudy, it can be decreased. These changes can be effected as many times in a day as you wish. Even partial closure is an option.
You can even change the length of the day by using blackout screen material during the summer months.
The opposite is true, too. Although less heat can get it, there’s also less heat to escape. This means that you may have to use supplemental heat if summertime temperatures dip or fail to materialise.
Screens enable you to regulate the climate – to create a little microcosm – in your glasshouse. Many growers, nurseries, and garden centres use computer software to make this work, though you can do it manually if you prefer.
A warmer interior also hampers the formation of dew which in turn reduces the chances for fungus.
Screens tend to last upwards of ten years. After that you need to think about replacing it and the cables that extend it. Over time, friction creates jagged edges in the cable which ultimately tears the fabric.
Even so, the cost of screen installation is more than covered when you take into consideration the savings you make in heating glasshouses without them.