Ever since I took biology in high school I have wanted to build a greenhouse. Greenhouses are a really cool way to grow larger and healthier plants faster and artificially extend the growing season. Greenhouses work by using a transparent airtight cover to trap in light and moisture to create a mini- ecosystem that is separate from the environment around the greenhouse. Heat is generated both from the sun’s rays that penetrate the greenhouse but do not escape as well as the trapped heat given off by the plants during their biological processes such as photosynthesis. This results in a very fascinating microclimate. This general idea of a layer of material trapping in heat and increasing the climate below is why sometimes global warming is called “the greenhouse effect” by people who like to oversimplify complicated climate phenomena.
Part 2) The Greenhouse!
We made our greenhouse in one afternoon for under $25. It was based on the French Cloche design that involves two semicircle frames and a cloth cover that is used to protect plants from cold and wind.
2) 10 foot long, ½ inch diameter PVC pipes
3) 40 inch long, ½ inch diameter PVC pipes
Roughly 25) 6 inch long Zipties
10 x 20 foot painters clear painter’s plastic tarp
1) First we measured my garden which is about 1 square meter (tiny I know). Then we used complex integration and approximation to measure the arc length of the frame. Just kidding. We just used a tape measure to approximate and then just used the 10 foot measurement that the PVC came in.
2) We used the hacksaw to cut the ends of the PVC pipe at an angle so that they could be easily stuck into the ground. To do this start about 3 inches from the bottom of the pipe and cut away from you at an angle.
3) Stick both ends of the pipe into the ground at opposite sides so that it makes a nice arc. We placed one arc behind and one in front of the garden. We measured three inches to the left and then another three inches away from the garden corners.
4) Next we placed one 40 inch PVC across the top in the center of the arc. We duct taped the ends to the arc. We placed the other 40 inch pipes about 9 inches on either side of the middle pipe.
5) Then we cut a large portion of the plastic to cover the frame. In all honesty we gestimated the size. We folded over the plastic so that the greenhouse was coated in a double layer. Feel free to do more than a double layer, but two layers is the minimum to ensure sturdiness. Once we draped it over the greenhouse, we secured it with zipties and cut off the excess on either side. We needed two people for the zipties because one person had to keep the side taught the entire time. We secured the plastic to the ground with picketed stakes.
6) To make the end pieces we cut a small piece of the plastic, doubled it, and then draped it over the frame making sure it could touch the ground. Then we simply just ziptied it to the PVC frame, making sure the plastic was held firm.
7) Finally we cut a slit in the front to make the doorway and secure the tear with pieces of duct tape.
8 ) The only thing left to do is use either duct tape or packing tape to tape around the sides and seams in order to make the greenhouse completely airtight.
9) Then we were joyful and celebrated because WE JUST MADE A GREENHOUSE!
Now the plants have a safe and happy home!
You may also secure the bottom edges with duct tape in the same manner as the door. After four straight hours we decided to leave the tidying up of the base until next weekend.
Adding a zipper to the front will help trap heat and moisture.
Only one top beam is necessary. We used three for cosmetic reasons, but they end up collecting pools of rain water.