For home gardeners it has been unthinkable, gardening year-round in a greenhouse, easy enough in the colder months of the year, but a supreme challenge in the hot growing season. In summer you are adding already hot temperatures to the greenhouse effect which naturally magnifies heat. Very intimidating. But sometimes things are not as bad as they seem. In actuality I am finding that you can indeed cool a greenhouse in summer. Maybe not cool cool, but just cool enough for plants to grow. Of course you will need an air conditioner. And do a little tweaking to make it work.
I first considered using a makeshift air conditioner such as found on YouTube. There are several on YouTube, and they all work similarly. I, and my wife, like the fact that they make use of inexpensive equipment, a basic house fan, a coil of tubing, a bucket of water and a block of ice. You also need a small pump to pump chilled water through the tubing which is positioned in front of the fan. You get the idea. But I decided in the end to go with a store bought portable air conditioner. My wife thought I was crazy; even I had some doubts. I had to relax hard held notions about capturing conditioned air in closed, insulated environment. I could forget that kind of thinking here.
In this situation the air conditioner alone will not be able to convert warm air into cool air as usual. That is because the warm air in this case is actually hot air to very hot, a much bigger job for the air conditioner to do. But not to fret; this only means that I had to help the air conditioner out a little bit. For one thing, my gardenhouse is equipped with a retractable sun screen that helps a little bit by blocking thirty percent of the sun light. Also, I created cross ventilation to remove some of the hot air so that the air conditioner would be more effective. I installed an exhaust fan at the highest point in the gardenhouse, since heat rises. Across from there I opened one of the lower flaps on the gardenhouse roof, just a little bit, as an air inlet, creating the cross ventilation between the two points, hoping mostly to siphon off the very hot layer of heat directly under the greenhouse material on the roof. Thus, between removing hot air at the top by cross ventilation and blowing in conditioned air at the floor level, along with the use of the retractable sun screen (and without having to completely open up the house as originally thought), I am able to hold temperatures in the upper eighties to lower nineties in peak hours of a summer day, quite suitable for growing most garden vegetables, the bottom line.
- Herman H.