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Jan 08, 2024

How to Build a PVC Greenhouse

Need a small greenhouse? A DIY greenhouse made out of PVC might be just what

Need a small greenhouse? A DIY greenhouse made out of PVC might be just what you’re looking for. Learn how to build a PVC greenhouse using plastic tubs and bubble wrap.

Over the years, I’ve often wished for a greenhouse to grow plants through winter. I didn't want to spend too much money to build a greenhouse that later failed, and purchasing a pre-built greenhouse was a bit too pricey for my pocketbook.

After a little research, I found the four basic principles necessary in making a functional greenhouse:

I took apart a "9 Square" volleyball game I’d built to get 1-inch PVC pipe parts to build the greenhouse, which would be 5.5 feet cubed (see Figure 1).

I wanted the door to be low-cost. I bought a larger PVC pipe and placed it over a smaller PVC pipe, and then I had the beginnings of a swinging door. I did have to get different sizes of PVC pipe for the door portion, but it worked (see Figure 2).

The design required me to add a PVC pipe in the middle of a wall, and I liked the resulting structural strength, so I also placed an additional pipe on the ceiling and on the opposite wall of the door. I could’ve placed additional PVC pipes on the remaining two walls, but I didn't to minimize cost, and the structure didn't really need it. If you live in a place with strong winds, your DIY PVC greenhouse would benefit from the added structure strength.

I considered what could be used for the walls and could only think of the rigid, clear, double-wall plastic sheets I’d used on a previous build. Then, my wife gave me a great idea: Plastic wrap. This made me think of the stretch film used to wrap pallets for shipping. Then, while considering packaging materials like stretch film, I thought of bubble wrap! Bubble wrap can be purchased in assorted sizes. The bubbles give the plastic R-value because of the trapped air inside them. Plus, it's cheaper than hard, double-wall plastic sheets.

I chose bubble wrap with 1-inch-diameter bubbles. I decided to use stretch film around the outside of the bubble wrap for better insulation. The bubble wrap would have some insulation, but adding the stretch film on top of it created more air pockets, so the walls and ceiling had better insulation properties. I probably could’ve skipped the stretch film and used two layers of bubble wrap with the bubbles facing each other, but I feared less visible light would get into the greenhouse, and that it would cost a little more because bubble wrap is more expensive than stretch film.

The entire cost of this small greenhouse DIY project was approximately $200, counting the cost of the materials used, but not leftover material, with about half the expense being the large tubs.

Unfortunately, I didn't document the initial building of the greenhouse. My son told me I ought to test the design before considering the DIY greenhouse of PVC a success. So, the pictures in this article were taken as I disassembled the greenhouse after a successful winter of proving the design.

Here is how to build a PVC greenhouse.

I built the PVC cubic frame using the appropriate corner connectors and didn't use glue. I wanted the capability to disassemble the greenhouse in spring and build it back up in fall. Once or twice in winter, a PVC pipe came out of its connector (usually after a strong wind), but even with the bubble wrap installed around the frame, it was easy to put the pipe back into its connector because I had full access to the frame inside the greenhouse.

With the door closed, I began wrapping the outside of the frame, ignoring the fact that the door was there, at first. I used packing tape to hold the bubble wrap to the frame at the start and whenever I felt it needed it. I started at the lowest level and wrapped the bubble wrap all the way around the frame, with the bubbles facing outward. Then, I started a new bubble wrap row higher up, allowing about a 6-inch overlap of the layers. I continued the process until I got to the top of the frame.

For the ceiling, I cut strips of the bubble wrap to a good length and taped them to the already installed bubble wrap using packing tape, and I used packing tape to hold one piece of bubble wrap to another. After the bubble wrap was installed, I did the same thing all over again with the stretch film on top of the bubble wrap.

At this point, the door was enclosed in the plastic wraps. So, I used a utility knife and carefully cut the plastic along the door seams, using packing tape to hold the wraps to the PVC door frame and door. This worked but resulted in the plastic wraps not being tight to the door when I opened it. I was okay with that, because the plastic wall would tighten up again when I closed the door.

I did have air gaps around the door that I felt were unacceptable. Those gaps would let cold air into the greenhouse in winter and compromise the insulation. I pondered how I could cheaply seal the gaps but still be able to open and close the door regularly. I went to a home improvement store and found vinyl and plastic floorboard molding and foam pipe insulation that would fit around the door frame. I purchased both items and installed them around the door using the self-tapping screws (see Figure 3). See Figure 4 for the door latches I made.

I then prepared the water tubs to go inside the greenhouse. While the tubs themselves were black, which is what I wanted for absorbing heat in the greenhouse, the lids were yellow, so I spray-painted the lids black. I didn't wait more than a day or two to put them into the greenhouse, so most of the winter, the greenhouse smelled a bit like paint. It didn't affect the greenhouse or plants at all, it just wasn't a pleasing smell. Next time, I’ll wait longer for the paint smell to dissipate before I put the tubs into the greenhouse.

I filled each tub with about 25 gallons of water, leaving room at the top of each tub so when I put the lid on, water wouldn't come out. With 10 tubs, I had 250 gallons of water to absorb the heat generated during the day.

The more water you place in the greenhouse, the more temperature averaging will happen, but you’ll start to lose room in the greenhouse and the cost will increase. I found this amount of water to be good enough for my purposes. See Figure 5 for the tub placements.

I monitored the greenhouse throughout winter, and it would get up to 30 degrees Fahrenheit above the outside temperature during a sunny day and stayed above freezing at night.

The packing tape seemed to hold fine until spring, when it warmed up and began to lose its stickiness. So, I had to add new tape to the greenhouse here and there along the way. The bubble wrap, stretch film, and PVC all held up fine through winter and will be reusable next year.

Karl Thorup is a Utah native and enjoys outdoor life and creating new things. He has a bachelor's in physics and a master's in electrical engineering. Karl has eight children and 16 grandchildren, and his wife is the gardener of the family while Karl is the facilitator.

Originally published as "DIY Greenhouse" in the April/May 2023 issue of Mother Earth News and regularly vetted for accuracy.