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by Alex Mantegazza
(Hampton Park, Victoria, Australia)


Greenhouse with automatic venting

Hi, I have a 4 meter x 5 meter greenhouse on a cement slab. The roof is milky corrugated polycarbonate and the 4 walls are clear corrugated polycarbonate. The 5 meter layout faces N-S. The east wall faces the sunrise. The east wall has a large screened window, the north and south wall have screened doors. In mid-summer it gets very hot in the greenhouse even with the 3 openings.

My question: Could I cool down the greenhouse a bit by putting 50% shade cloth on the roof and covering the east wall? Would there still be enough light getting through to sustain my veggies?

Any help you can provide would be appreciated.

Comments for Greenhouse roof shading

Dec 07, 2019
It Depends
by: Jacki Cammidge, Certified Horticulturist

It really depends on what vegetables you’re growing. Crops like tomatoes, peppers and the like really appreciate lots of light, and don’t mind the heat so much. If most of your crops are greens, especially lettuce, they prefer shade.

Using shade cloth will cool it down a bit, and having some kind of ventilation fan will help too, so maybe consider that as well.

Another way to cool it down is to keep the concrete damp as the moisture will evaporate – this is called evaporative cooling, sort of the same way that sweating in hot temperatures acts to cool us off.

As you can see in the picture of the greenhouse (above), they often have vents that open automatically as the temperature rises – this might also be a good option.