Shards of glass
You need shelter if you don’t want shards of glass.
Photo: Grøn Kommunikation
Wind and water can be a dangerous cocktail when there is too much of it.
Gone with the wind
I have for many years had a greenhouse. I have had different models and none of them has been blown down. Through the years there has been many storms and even hurricanes.
3 years ago, I helped my son and daughter in law put up their greenhouse. It was cast to a footing. 3 weeks later it collapsed. They live in western Denmark where the wind is blowing hard, but it was a powerful wind from the north that blew it down. Fortunately, the insurance covered the damage and they put up a new one in a more sheltered place.
If you place your greenhouse right by the ocean with no shelter, you will regret it.
Photo: Ole Lund, Ålbæk
History shows how important shelter is. You can glue the greenhouse with silicone as much as you like, but if it is not sheltered from the wind it is still vulnerable. If just one window is broken, the wind can get hold of it and blow the greenhouse down.
Plant a hedge
In England, the average wind speed is 8.2 knots. If you don’t want a broken greenhouse then you need to create shelter. A dense fence can shelter a greenhouse, but the wind will then blow upwards and over the fence, which can create rather powerful turbulence on the other side. A fence should therefore not be completely closed off but have small cracks where the wind can blow through. The effect of the shelter will be better if you have bushes in front of the fence, where the wind can blow through. In the long run, a hedge is probably the best solution. The many leaves and branches of a hedge will hold back 60-70% of the wind. Evergreen is the best. The hedge should not be placed right next to the greenhouse, so it covers for the sunlight. Put it in a fitting distance. As a rule of thumb, a 6.5 feet high hedge provides shelter in a 32.8 feet distance.
Wickerwork is a fast solution to provide shelter.
Photo: Grøn Kommunikation
Glue and profiles
If you glue the glasses to the profiles with silicone you strengthen the construction. Silicone is flexible and protects the brim of the glass, so it won’t break. But without shelter, you still risk your greenhouse blowing down. The last factor is the house’s profiles. They matter especially when there is wind gust. Thick profiles are not necessarily tantamount to stronger profiles. The best way to test them is to pull in them. If they bend easily, the wind will also bend them easily. If you have profiles that are not so strong, then make sure to stabilise the corners and preferably put up struts crosswise the house.
Water from above
If you glue the glasses on the greenhouse with silicone, you will get a tighter greenhouse. Greenhouses are rarely completely tight. They are built to collect heat and small leakages just contribute to the necessary ventilation. Roof-lights on a house are sealed with rubber strips and different profiles, therefore one roof-light can be as costly as a greenhouse. Though roof-lights can also leak. Just a 0.04 inches hole can be large enough for water to get in. Sometimes even a lot of water, it depends on the wind. Moreover, it can be very difficult to find the hole. I myself had a large rooflight which leaked and was first fixed 10 years after it was put in. Tree different professional companies were on the case before it was solved.
Today many use their greenhouse to lounge in, and then it can be annoying if the water is dripping right where you are sitting. If you have a greenhouse that leaks a place you don’t want it, then silicone is the solution. You might miss the small hole at first but try again. Be aware that the water might slide down the profile and drip an entirely different place than where it originates from. Finally, greenhouse glass is not insulated, so condense water will also drip.
Put something in the corners to increase the stability.
Struts are something you can put up yourself and they don’t need to be strong.
Om Lars Lund
Danish horticulturist and journalist
Lars Lund has for many years engaged in the garden and greenhouse. Lars has published many books about greenhouses, and he has participated in many Danish horticultural TV shows. He is a walking garden encyclopaedia, and he has answers for most basic cultivation questions – also the more ambitious ones.