Johannes-Ulrich Urban via pbs
Fri, 08 Jan 2021 08:17:32 PST
Hello Luminita,

There are so many excellent comments on greenhouses, here is my personal experience.

I am on my fourth greenhouse here in Portugal and I would recommend the following: as much ventilation as possible. Many comments have stated that, it cannot be overdone. I noticed that some of the models in the attached catalogue do not have enough windows or louvres. Do order as many extra ones as possible! I prefer widows because louvres are not closing tight enough when it comes to heating, otherwise they are fine as you can direct the air flow. I use non electric automatic openers, very reliable.
Shading: try to get a structure for (removable) shade cloth on top of the structure which bears the glass. If there is a space between shade cloth and glass which allows air to circulate, shading will be more efficient than with shade cloth lying directly on the glass. This is my problem right now. This space has to be big enough to allow the windows in the roof to open fully. At the same time such an extra structure is a perfect protection against hail damage.
If the shading is removable in winter you gain a lot of light and warmth.
The door: try to choose a model which is tall enough so that the door can be put anywhere. This gives you a lot of flexibility. Make sure the door is wide if you need to move large plants, bulky material or a wheelbarrow.
Mice: make it mouse proof from the beginning. Stand the frame on  a floor of slabs or make a concrete or wall foundation deep enough to stop mice from digging underneath. 
Choice of glass: take greatest care which material you choose. Classic single pane glass, double glass (very good insulation but EXTREMELY heavy to manipulate) acrylic glass or polycarbonate glass and also horticultural films. All these materials have their own advantage and disadvantage and, very important, all have different properties when it comes to light transmission. I lost an entire winter growing Oxalis collection when it was moved from a greenhouse with acrylic glass in the roof to another one which had triple glass required by the local building authorities. The triple glass in the roof absorbed so much of the light spectrum (unnoticed by the human eye) that the Oxalis dwindled away within two or three years. There are high tech professional horticultural films with almost 100 percent light and spectrum transmission. It all depends on what you want to grow and at which season you want to use your greenhouse.

And last but not least...... I can only confirm that a greenhouse should be as big as ever possible...... not only for space reasons but also because it becomes the easier to manage temperature wise the bigger it is.  It will be the place in your garden where you will spend most of your time....

I am also more than happy to answer more questions.

Happy planning!


Please find attached a picture of my current greenhouse. Note that the walls are high enough so that the door could be anywhere. And note that the shade cloth is directly on the glass which is a compromise. The walls will be painted with white reflecting paint in summer. And yes, there are not enough windows..... 5 in the roof and 4 in the walls.

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