On a sunny day greenhouse can get very hot rapidly. Make sure that you are opening doors and vents every morning to reduce the heat in the afternoon. However, you also need to shield plants from intensive sunlight. There are four ways to shade a greenhouse but I personally recommend investing in a shade cloth.
If you want to cool a greenhouse without electricity, installing shade cloth will minimize the amount of sunlight passing through. Hence, it cools down the structure too. Although installing it is easy, many growers question if you should put shade cloth inside or outside a greenhouse?
Installing shade cloth inside or outside a greenhouse depends on the size of your structure and on what plants you are growing. Generally, installing shade cloth outside a greenhouse is very effective as it blocks sunlight before entering structure which increases cooling effect.
In this post we are going to talk about pros and cons of external (outside) and internal (inside) shade cloth installation. I would recommend to refresh your knowledge about shade cloths. That is why I put together a blog post where you can find everything that you need to know about a shade cloth.
Shade Cloth Inside Vs Outside A Greenhouse
You can use shade cloth either on inside or outside a greenhouse structure. The main advantage of installing the shade cloth outside is that it blocks some sunlight before it enters the structure. That way you can maximize cooling effect.
In comparison, installing shade cloth inside the structure will allow radiant energy to pass through the plastic. Once it is inside, it is much harder for energy to escape – think about the greenhouse effect! The main advantage of installing shade cloth inside a greenhouse is energy conservation.
Also, shade cloth inside creates blackout conditions but is worse in excluding solar radiation rather than external installation. For example, sometimes gardeners install black shade cloth inside a greenhouse to block sunlight entering the structure.
Black shade cloth absorbs this blocked out radiation and coverts this energy into heat. It can be beneficial for someone who wants to retain heat. However, for cooling effect you need to choose a shade cloth that reflects the solar radiation and doesn’t absorb it.
Whether shade cloth is going to absorb or reflect solar energy depends on the material it is made of and color. Lighter shade cloths reflect sun’s energy and do not alter the spectrum of the light. Check what is the best shade cloth color for your greenhouse.
Also, different types of plants can benefit from a specific shade cloth color at different growing stages. Find out what is the best shade cloth for orchids here! Although there might be some heat mitigation with shade cloth going inside the plastic, it is not going to be significant.
Another example of using shade cloth outside vs inside is when growing cacti in a greenhouse. If you want to have shade cloth inside, then you need to get a white 50% shade cloth. However, installing shade cloth on the inside will have the same effect from using either white or black at 50%.
How to install shade cloth outside a greenhouse?
If you decided to install a shade cloth outside a greenhouse, you need to order a custom shade cloth according to the size of your structure. Make sure that it is slightly over sized. That way you can provide complete coverage.
Buy a shade cloth with taped edges with grommets for tying the cloth down with rope. For additional security, take the rope to tent pegs in the ground instead of fixing it to the structure itself. This installation ensures that shade cloth will withstand heavy rains and strong winds. Also, it will help to reduce the load on a greenhouse.
Although installing shade cloth outside a greenhouse is very effective, the cloth itself tends to be more expensive. That is due to the extensive structural and mechanical requirements. Moreover, fitting outside of the structure is harder to arrange.
Some growers have concerns about shade cloth flapping in the winds if installed outside. It can damage the glazing or rip the cloth. However, due to its open structure, wind can pass through the shade cloth as well. So it won’t constantly flap on the greenhouse plastic or glass cover.
Also, you can cut shade cloth. For example, if you don’t want it to cover vents or windows. Whether it is going to fray depends on the material a cloth is made of. Knitted cloth has lockstitch construction that prevents it from fraying if cut. However, woven shade cloth will fray, but it is heaving which results in a longer lifespan.
How to install shade cloth inside a greenhouse?
You might want to consider internal installation as it will protect a shade cloth from nature elements. To make it easy to install buy a shade cloth that comes with pulleys, grommets or roping. String lines along the wall and up to the center of the roof. Fix pulleys on the sides of the greenhouse to draw the cloth up.
Clip the edges of the shade cloth to the lines with grommets on the edge. You can run a line along each of the two longest sides in the structure. When you draw a shade cloth from one end of the greenhouse to the other it provides extra cover for the plants.
Installing shade cloth inside a greenhouse can be beneficial if you want to prolong the lifespan of the cloth. It is likely to biodegrade over a few years if you install the shade cloth outside. Also, if you have a really attractive greenhouse, external shade cloth can spoil the whole look.
Installing shade cloth inside ensures that your greenhouse’s appearance is at its best while shading plants at the same time. For a very hot climate you can get white shade cloth, so it reflects sunlight and prevents heat build up inside the structure.
There are a few common concerns regarding the use of internal shade cloth. First, the dirt might build up between the cloth and plastic that is going to be hard to clean. Secondly, it can be harder to take the shade cloth of to clean it.
To sum up, if your main goal is to reduce heat build up inside the structure, install shade cloth outside a greenhouse. Make sure to fix it to the ground stakes rather then to the structure itself for security. If you want to absorb solar radiation and convert it to heat, install shade cloth inside a greenhouse.
The cheapest option would be to buy a shade cloth in a roll and cut it to size yourself. For this purpose choose knitted cloth as it is not going to fray. For someone who wants to improve cooling and monitor light transmission in a big greenhouse, I would recommend purchasing external blinds.
It is going to be a little bit more expensive but overall a good investment in a long run. Go for a model made of aluminum that is rust resistant and make sure it is easy to operate. Let me know if you would like a blog post on internal and external blinds!
Did you install a shade cloth inside or outside your greenhouse? Share your thoughts in the comments section below!