How We Cool Our Greenhouse


There are multiple ways to heat your greenhouse; but a lot will depend on your budget.

This post is meant to help out the backyard gardeners; those of us who can’t afford the big fancy cooling systems that are used in commercial greenhouses.

Being in New Jersey, we often get very cold winters and very hot summers; often to the extreme, so we had to prepare for both seasons.  

Below are things we do to help keep our greenhouse cooler in the winter:

Tips For Cooling Down The Fish:

 If you have an Aquaponics garden or just have fish in your greenhouse, you will need to keep them cool as well. To do this, I:

  1. I learned that because of the nature of Aquaponics whereby the water flows from the fish tank to the grow beds, into a sump tank then is pumped back to the tank; the water cools down a bit on it’s own. Not so good in the winter, but it does help in the summer. 🙂
  2. Clean out, then fill large 2 litre empty soda bottles 3/4 of the way up with water. Place them in plastic shopping bags and freeze them. Throw them into the fish tank to slowly cool down the water as the ice melts. When they’ve melted, rinse them off really well and let dry; then place into plastic bags and refreeze.
  3. We loose quite a bit of water to evaporation;  In addition, when I’m in the greenhouse I will take water from the fish tank and go around watering my plants. This usually uses up quite a bit of water, and provides room for me to run fresh water into the fish tank, equating to a water change every other day if not every day. Having well water, this helps cool down the fish tank.
  4. Make sure you position your fans all pointing one way in the house. Ours goes from front to back. Somewhere I have a great article that explains how to position them and why… once I find it I will add it to this post.

Tips For Cooling Down the Greenhouse:

Plants can begin to show signs of suffer when the temperatures reach 85 degrees (F). 

  • Providing your plants with a decent flow-through of air is probably the most beneficial thing you can do for them in the heat.
  • While it is still relatively cool in the early morning, it helps to open the vents and doors to help get cross-ventilation going; in my case we run box fans in the front of the greenhouse to push the fresh air in then we line fans up to continue the movement to the end of the greenhouse where exhaust fans then blow the air out the back of the house. These fans are automatically set to run a couple of times during the night then again in the morning to keep the air moving.

Not until after you buy and set up a good shade cloth on your greenhouse, will you realize what a difference they make!

Make sure you get the right density of shade cloth; we bought 40%, meaning that 40% of the UV light is omitted from entering the greenhouse. This is enough light for the plants to grow, yet it made a huge difference with the heat.



Plants do much better in the heat when they have plenty of moisture on their roots. 

Most of my plants are in self-watering containers which keep their roots damp but not soaked. When the water is used up, a floating valve lets more water in until the reservoir of water beneath the plants are full again. Excess runs out of a strategically placed drain hole so roots won't rot.

Adding moisture to the air will help your plants as well. The leaves lose moisture through their pores. This cools down the leaf surface, alot as like when you sweat; which is why you need to provide your plant with more water from the base to soak up.

Add humidity to the inside of your greenhouse. This can be done by running a misting system in the walk-ways or paths in your greenhouse.

When the sun and heat hits your greenhouse, the physical process of the water evaporating  (which itself uses heat), will lower the temperature in the areas where the water is evaporating. This is the concept behind Swamp Coolers.

You can also mist your plants themselves in the early morning. This will allow their leaves to dry out during the day, avoiding mold from growing on the plant.

Depending on the level of humidity in your area, by way of evaporation, Swamp coolers are said to cool down a very dry area as much as 25-30 degrees!

As you might expect, the size of the swamp cooler depends on the size of your greenhouse.

I have seen them coming down in price at some garden centers; I have also seen DIY projects where you can make one yourself.

Watch my BLOG posts as these are two items on my list to Blog about!

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I'm a gardener, posting related things as I find the time. There is a lot of great info I was keeping in folders; then realized there are others who might benefit from my research so I decided to share my findings online and get input from others.

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