HIVE.1 an Experimental Low-cost High-efficiency Greenhouse

Unlike a lot of greenhouse kits and diy builds I have seen, the HIVE.1 is a greenhouse built on the Stromberg Starplate system. I chose this system over other prefabricated kits or plans for a host of reasons. It assembles quickly, can be built on the ground, a solid foundation, piers, or a sidewall. The kit uses standard 2x2, 2x4 or 2x6 lumber- a LOT less compared to every other greenhouse design, including some a lot smaller than this. Since all of the studs are the same length, there is very little (or even zero) waste when framing. The basic design and layout of the greenhouse will always be the same, however it allows for the builder to change, upgrade, or remove different materials according to budget or season. Although it looks small, and has a small footprint, the interior space is much larger than it appears. This comes down to the greenhouse being pentagonal instead of square or rectangular, and the height (having used standard 8ft 2x4's) is around 14ft from the ground to the peak. It really is an astounding system and although I was able to find a small handful of short videos online of people who have framed or sheathed the same system there really isnt any detailed information on the Starplate brackets. During the pandemic, when everything including and especially lumber was soaring in price I recognized the value of using these brackets to build and document what has already proven to be a low cost and extremely efficient greenhouse for the small farm, homestead or backyard gardener.

Stromberg's Chickens- a partner of Mann Lake Bee Co., has been producing and selling a bracket kit for years that utilizes standard dimensional lumber to bolt together a polyhedral frame of equilateral triangles. The framing system can be used to construct all manner of enclosures from sheds to carports and small/temporary cabins. It allows even novice users with little or no construction equipment or minimal tools to quickly erect a strong and inexpensive shelter. Having started plants and seedlings indoors for the past few years, blocking the large french door in our dining room with wire shelving, running fluorescent lights all day and getting dirt and water all over the floor I decided it was finally time to build a small greenhouse behind our house. With the high cost of lumber and spring rapidly approaching, this greenhouse build checked every box on the list. As I write this instructable, the greenhouse is finished, but it is continuing to evolve. I will continue to add and refresh this instructable as the seasons change this year, offer my insights on how it has continued to perform, and likely link to other instructables on additions (because we are in the warm months I have not yet added a heating system to it, etc. That, along with some automation, irrigation, and general projects are all currently still in the works). This instructable is focusing on the actual how-to and why's of the greenhouse construction, the interior, plumbing, and potting bench.

The list of supplies to build this project is pretty expansive, but depending on what you plan to build does not need to be. Think general diy and home power tools- Instead of listing everything here I will be listing the tools used at the start of each step. At the very least you will need:

-AT LEAST ONE HELPER. Having a second set of hands means you can get the frame cut, drilled, and bolted together in a matter of hours- if not less.

-The Stromberg's Starplate bracket kit. I opted for the kit which included a rain cap and the carriage bolt hardware

- 25 equal lengths of 2x2 or 2x4 lumber in your desired length

-a saw (if you want to bevel the ends)

-a powered drill

-a socket wrench or even a box wrench

-a shovel and/or post hole digger

Tools used for this step: chainsaw, hatchet, miter saw, socket set/impact driver, string, line level, mallet and rebar stakes. Choosing an adequate location for any greenhouse may be the most crucial step toward its construction. The greenhouse needed to meet the following criteria in order to justify this project:

-I wanted something close enough to the house and driveway that we would't have to drag materials, soil and plants across the property. I also wanted it to be within reach of the hose faucet on the house, until later in the season when there is time to trench and run a connected water line to the greenhouse.

-The greenhouse needed to be in full morning sun, in the path of the sunlight a majority of the day, shaded from the afternoon sun. This allows for the greenhouse to come up to temperature quicker after cool nights, and stay warmer through the day. I had planned all along to use a solar powered vent fan from our quail enclosure, so full sunlight during the day provides the fullest available power to the solar panel- providing less power through the late afternoon and evening as the sun drops behind shade and horizon. This in turn slowly powers the fan off while it is still light, allowing the temperature to remain warmer as the sun fades.

-the base of the greenhouse needed to be built on the most level ground possible. This was a very limiting factor as much of the property is uneven or rolling. From a birds eye view, our house basically sits at the base of a giant earthen bowl.

-The structure also needed to be far enough away from the house that it wouldn't be a hazard or nuisance if it were to somehow collapse or be blown over.

What this all left was a nearly perfect spot. Nearly, because there was a large eastern redbud tree almost exactly where the greenhouse needed to be. This was taken care of using a chainsaw and hatchet. The stump still remains, and after sitting through the spring I plan on plugging the dead wood with mushroom spawn and letting nature slowly eat it away while simultaneously harvesting the fruited mushrooms.

Tools used for this step: Impact driver, masonry bit, socket, post hole digger, shovel, miter saw. I chose to use footings as the base anchor for my greenhouse. I live in a northern climate and am aware of the frost line and heave, however time was a large factor in this build, and the area where the greenhouse sits is very hard compacted clay fill. I also did not have the auger connected to the tractor and didn't have a helper on hand to assist in mounting it- otherwise it would have likely been built on a pier foundation. These footings are very inexpensive and usually sit ON the ground to support floating decks. I chose to fully bury the footings and compact the clay over them, and support the structure on 4x4's that are lag bolted into them. I know it looks and sounds unorthodox, but this method turned out to be surprisingly stable and sturdy. I dug out an area slightly larger than the footing itself to allow for some movement and adjustment when bolting the frame to them. The 4x4 lumber is also lag botled to the footing though a hole drilled in the side with a masonry bit.

Tools used for this step: drill driver/impact driver, or a socket wrench or open ended wrench. This is the fastest and easiest step in the entire build. It is pretty straightforward- once the footings, or basewall, or pad is in place and level, the frame bolts together quite easily. It helps to have a second set of hands for the first couple side walls, but I just used a couple lengths of lumber to prop it up. Once all of the sides have been bolted together, I went back and tightened each bolt down to take up the slack and draw it all together tightly. This whole process took me less than an hour, and it was getting dark and cold so I called it a day. The following day I enlisted the aid of a coworker to help with the rest of assembly.

Tools used for this step: tall freestanding ladder, socket driver, somebody to assist. Once the walls were bolted to the footings, and tightly bolted together, the final step for the frame was to bolt together the roof assembly. This does require two people, one on a ladder to bolt the struts together in the center peak, and someone on the sides to bolt the roof struts in place to the walls. Since the Starplates are very heavy gauge stamped steel and pre formed to hold the lumber in position, this process only took about 30minutes with the aid of a second person. It is also a good idea to always have another person around when you are doing any sort of work on a high ladder, especially on uneaven ground.

Tools used for this step: Drill, bits, neoprene washer roofing screws, free standing ladder, heavy duty clear tape, circular saw, saw track system, utility knife, straightedge, ruler, permanent marker.

NOTE: This step is where it is up to you as to how much you want to insulate or spend on enclosing the greenhouse. Initially we had planned to wrap the entire frame and structure in greenhouse plastic sheeting, much like heavy duty plastic dropcloths. Knowing full well though it wasn't going to be a permanent feature, as well as being more fragile and susceptible to environmental damage the decision to use greenhouse film was quickly abandoned in favor of polycarbonate multiwall panels. Spending the time and money on rolls of plastic I was going to be removing and likely sending to a landfill seemed like a complete waste all around. The panels are a lot more expensive than plastic sheets on a roll, but they insulate extremely well, have a far longer lifespan, and are the most durable choice you can make for any greenhouse. Each triangle of the greenhouse only uses one 4'x8' panel cut on a diagonal. One side of the panel is coated for UV protection, so every other panel was cut on a reverse diagonal line and the pieces were mated up with one another so all sides of the greenhouse are facing out with the UV coating exposed. Cutting these panels initially used a circular saw and guide track. not only was this loud and messy, and tore up the edge pretty badly, it was also unnecessary. All you need to do to cut the polycarbonate panels is to use a sharp utility knife and score pretty firmly a couple times. The panel will snap cleanly right along the scored line much like glass. The panels are all attached to the wood frame with neoprene washer backed screws to keep water from getting inside the individual cells which decreases the insulating effectiveness and can condense, generating mildew inside the panel walls. Water can also build up and freeze inside during the winter, eventually breaking the cells open. the panels would need to be replaced at that point. To further mitigate water intrusion, I used heavy duty clear duct tape to seal the top-facing edge of each panel before screwing it down.

The roof is a lot more awkward to screw into place than the walls. What we found is that it is easiest to stand on a ladder inside the structure, and work your way around in a circle until you reach the last area. Have somebody outside the structure to hold and guide the panel in place from the ground. Once the last area needs to be fastened, it is easiest (though still tricky) to screw that panel down from atop the ladder, but from outside of the structure. Knowing this beforehand, we made the choice to get the roof secured first, since this allows the person at ground level to easily step in and out of the side wall framing.

The side wall edge that rested on ground level was left open, since this is where the doors will go in the next step.

After all of that, the final step was slowly bracing ourselves along the roof struts to reach out and drop the roof cap down over the peak It is tightened from inside using a long through bolt supplied with the kit.

Tools used for this step: Miter saw, drill, bits, screwdriver, utility knife, construction screws, neoprene backed washer screws, tape measure.

Doors for these structures can be built a few different ways, depending on the needs. The walls can be built vertically either all the way around or just where a door will go. this requires additional lumber and bracing, and the resulting frame isn't as sturdy. A regular rectangular door can be framed inside of the triangular wall, but it will be both narrow and shorter than a standard door. I wanted to be able to easily carry plants and materials through the doorway so I decided to build 2 triangular frames that fit snugly inside the frame that opened up and away from the center. These are held along the outside edge with three inexpensive door hinges each. The draw back to building a door this way is that they angled slightly downward as they are opened, and will dig into the earth if that edge of the frame is sitting level on the ground. the solution was to dig out a short “step” down into the ground below the door to allow clearance. I will be digging this out a little deeper soon and then setting pavers down so that it doesn't look like a large patch of dirt pulled from the ground. There is a small section above the two doors where a gap was left. I cut and beveled a piece of scrap wood and screwed it into place to help seal it in. As it gets cooler, there will be a small insulated panel that will fit this whole space. For the door handles, I made a simple set of pulls using some nylon webbing from an old ratchet strap and screwed them to the door with a nice washer that recessed the screw head. To hold them open, I just affixed an eye bolt to the bottom corner and 2 eye bolts to the frame on the sides of the doors. A piece of heavy jute rope and a carabiner has held the doors steady even on a day with severe gusts of wind. The doors are very light and easy to fold back and clip open.

Tools used for this step: Drill, screwdriver.

Figuring out a way to close the doors and keep them closed turned out to be a bit of a challenge. The way the doors are tilted, angling downward slightly- causes them to sag away from the frame slightly. There is no center support on this face of the greenhouse because it would be in the way of entry and exiting. Initially I was using a latch at the top and bottom of the doors, but like any french door the needed to be locked to the frame individually, not to one another. I wanted to keep the cost of this build down and come up with a simple solution for other people who decide to use this instructable as a guide. My solution was to pick up a pack of heavy duty T latches online and use them to draw the doors tight to the frame. The latches were inexpensive, are built for heavy use, and are made for prolonged outdoor exposure. They work well, and drop out of the way when not being used to hold the door shut.

Tools used for this step: Miter saw, drill, bits, screwdriver, construction screws, solar vent fan.

I knew from the beginning that I was going to need to draw cool air in and Vent hot air out. Not wanting to build large frames and open panels on the roof for manual or automatic vent openers, (which would have cost materials, more parts, and a lot more time) I instead opted to vent the hot air out using a solar powered vent fan. These are available in a lot of volumes of air evacuation and power ratings but are all the same concept- a small dc fan motor wired directly to a solar panel. When the sun is out and shining, it powers the fan full blast to move hot air created from the sun inside the greenhouse. When it isn't as sunny, the fan moves slower, and theres less hot air trapped inside due to the lower sunlight. These fans are available on sites like amazon and eBay and can be purchased pretty reasonably. The fan I am using was on an enclosure used when we reared quail, and although small it moves a lot of air. I built a frame for it out of scrap lumber and offcuts from the project, then cut a hole as high up on the wall as possible while staying under the overhang of the roof to prevent rain from getting inside or on the fan itself. On the outside of the panel, I made a simple wood frame to cover the exposed edges of the vent hole and ran the power line to a solar panel mounted on the roof facing directly into the suns morning and afternoon path. I’m not sure about the panels placement right now and have other solar powered projects planned for the greenhouse. More than likely the panel will be relocated and combined with others in a small array in a future added step. 

Tools used for this step: Miter saw, wood glue, ratchet straps, construction screws, spray paint, heavy duty stapler.

To aid in evacuating hot air from the greenhouse, it is important to draw cooler air in from outside. I placed vents in the wall facing away from the sides that get the most sun during the day, as close to the ground as possible. being opposite from the exhaust fan, this creates a stronger crossflow of air throughout the structure, circulating the air inside and helping to maintain a more even and temperate environment. Using 1x1x4’ landscaping stakes, I set the miter saw for 60 degrees and beveled the ends of sets of 6 equal lengths for each hexagon. The hexagons were glued up to one another (my compressor broke, or I would have pin nailed them as well) and clamped them into play using ratchet straps. after the glue had set and dried, I masked off and spray painted each of them. Only two of the smaller hexagons are actual vents, and I spray painted and then stapled some aluminum “beehive” mesh to the back sides. I already had the mesh for a large hanging solar lamp I am building for the interior of the greenhouse, but you could use any outdoor rated mesh or screen. Once they were built and painted, I mounted the large cells first by screwing from the inside of the greenhouse through the polycarbonate panels and into the frames. Holes matching the interior diameter of the vents were cut from the greenhouse panels and taped off to prevent rain and water from getting inside the panel cells. 

For the base wall, I went with the corrugated steel panels. They are easy to cut, and sturdy on their own. To help keep pests out, prevent drafts, and make a good seal, I dug a shallow trench along the sides of the greenhouse then dropped the panels in the ground. After backfilling the trench I bolted the panels to the lower edges of the greenhouse base.

This is as far as I can get right now until I am able to edit and upload more photos and steps for the peripherals of the greenhouse, but for now this concludes a functional and completely useable greenhouse. The following steps will all be mini-instructables of their own, rather than writing and posting individual posts for each. That way they are all in one place. This will include the flooring, the raised bed, the potting bench, the hose manifold, and misting system, and eventually the electric and heating system for next year. Stay tuned