Butterfly

While I was filming my latest video, this butterfly landed on my hand.  In the past, I’ve received several questions about why I don’t put screens on the greenhouse vents…this is why!

(Sorry it’s blurry, this is a screen grab from the video and the camera wasn’t focused for the close up shot!)

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The end of the normal growing season

Today marks the end of the season for the “sustainable” greenhouse. Last night was the first night the heaters needed to run to keep the plants from freezing. (The heaters are programmed to turn on at 36F). My outdoor growing season ended just shy of 2 months ago so I’m still quite pleased with the extended growing season!

My definition of “sustainable” for this project is not having to add extra heat or lighting for the plants to grow, The other electricity for the pumps and automation is an integrated part of the greenhouse Aquaponics system and I classify that as part of the normal functions. ;-)

I still have peppers, tomatoes, and lettuce growing which should survive for the winter. Of course the cost to keep these plants alive will now skyrocket in electricity costs, but it’s still a nice treat to get a few fresh veggies during the winter.

Already looking forward for spring!

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How To Build Your Own Strawberry Tower

By popular demand, heres a video detailing how I build my strawberry towers. I hope you find it helpful! Full transcript is below. Click on the video image to watch in HD!

Hello everyone.

One of the top requests I get is how to build a strawberry tower. This video will display all the necessary steps to build your own.

The first step is to place a mark on each end of the pipe, then rotate it 180 degrees and mark the other end. Then snap a line down the entire length of the pipe. You could also use a straight edge to mark a line, but I find the chalk line to be more accurate and easier. Turn the pipe over and snap a second line down the opposite side.

Along each chalk line you will place a series of marks. Starting at 2 inches, draw a mark every 8 inches. This will be the spacing between each pocket in the tower. If you are going to grow plants that need more root area, set the spaces further apart. I typically replace the strawberry plants every season. If they grow for more than one season, they can become root-bound.

Starting at the first set of marks, draw a line from one mark and connect it to the mark on the opposite side. Then turn the pipe 180 degrees and connect the next series of marks. Continue rotating the pipe while connecting each series of marks. These lines will be used for cutting the slots in the tower.

Along each cut mark, carefully cut through the pipe until you reach the measured mark you placed at the chalk line. Do not cut through more than half the pipe! Rotate the pipe 180 degrees and cut the next slot. When you are done, each slot should be on the opposite side of the previous slot.

Time for some good gloves. The pipe doesn’t become flexible until it is well above the boiling temperature of water. Please be careful!

The general area that will be heated will be an arch shape starting at one end of the slit, up about 8 inches to the back side of the neighboring slit and then back down to the other end of the slit.

Heating PVC should be done in a well vented area. If you overheat it, it can release some nasty gases. Please be careful! Continuously move the heat around the arched area. Try to avoid heating the area below the slit to keep the pipe from bending too much.

After a few minutes, the PVC will become soft. It helps to apply a little extra heat at the each edge of the slit since this is where the sharpest bend will be.

Push in the PVC so it makes a concave shape in the arched area. You will want to push it in enough so that it will touch against the back wall, but not create a seal since the water will need to trickle through that area, but don’t leave too big of a gap so your growing media will fall through it. When you let go of the pipe, it will usually spring back a little, leaving a gap around ¼”.

I found it to be very helpful to use a few spring-clamps to hold the tight bends in place while the plastic is cooling. You will want to hold the shape in place for a couple of minutes while it is cooling.

It takes me about 3 1/2 minutes to completly create each pocket.

When you are done, you will have some nice pockets alternating on each side of your new tower.

As the water flows through the tower, the surface tension in the water can cause it to flip out of the edge of the slit. To correct this, I added a collar around each pocket.

With some extra pipe, cut some rings about 1 ½” wide. Then remove enough of the ring so when it’s placed over the slit area, it extends just beyond the slit. Add some silicone adhesive and clamp the ring in place. Half of the ring should be placed above the slit line. Use clamps to hold it in place until it cures.

If you’re not going to be draining directly into a sump tank, you’ll need a way to catch the water from your towers. Take a 4” cap and add a fitting to it. Drill a 7/8” hole and thread it with a ¾” tap. There are several ways of adding fittings, but I found this to be very cost effective method.

Take a ¾” NPT to barbed fitting and screw it into the tap. If it is screwed in far enough, it will be higher than the base of the cap. This work well to help any media that as fallen through from going down the drain and clogging it.

This cross-section shows how the fitting is placed into the cap.

Place the cap on the bottom of the tower. The bottom pocket should not be filled with anything so you can clean the base cap if necessary.

To hang your tower, drill a couple of holes on both sides near the top and insert some S hooks. Use a wire or chain to hang it from a strong support.

To connect the tower drains together, you can attach them with tubing and barbed fittings. I made some stands from scrap 3” pipe to support the bottom of the tower. Then I used a 1-1/2” pipe with holes drilled in the side to catch the water from each tower. Each pipe then drained into the main sump tank.

Filling each pocket can be a challenge so I made a tray-type funnel to speed up the process. Take a section of pipe and do a cut down its length. Heat the entire piece so it can be flattened, then bend up the edges so it forms a V shape.

I created a cross-cut section so you could see the inside of the tower. Please note that this sample is done with black ABS so you could see the various surfaces easier. Each pocket will hold about 5 cups, or 1 liter of growing medium. This is enough space for most shallow root plants like strawberries or lettuce. For my strawberry plants, they will usually get water for 10 minutes every hour and a half.

Thank you for watching. Here’s a quick slideshow of my strawberry towers in action!

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Plastic Extruder for Growing Media

For several months, I’ve been developing a plastic extrusion system that has been able to take virgin HDPE resin pellets, or shredded milk jugs, and properly melt and extrude them into a shape that could be used as a low cost growing media for my Aquaponics system.

There was a lot of trial and error to get to this point. The biggest problem is that the plastic retains little moisture. If the seeds aren’t directly placed in the flood/drain cycle, they won’t get any moisture to germinate. I typically grow in stone and some of the stone above the water line is able to wick and retain enough moisture to provide water to new seeds.

Another issue with HDPE is that it’s extremely smooth (again, works well to repel water). Even adding texture to the media during the cooling process, the media still is smooth, which makes it difficult for bacteria to stick to it. I was also a bit surprised to see that the roots didn’t really care to grow in it and they would grow around the edge of the net pot instead.

On the plus side, the plastic is light, fairly inexpensive, clean, and easy to work with.

I hope some of the info in the video is useful to some of my fellow aquaponic/hydroponic growers in their quest to find a better, more cost effective growing media.

EDIT:  There is now a second blog entry with some more details about this.... Click on the "Newer Posts" link near the bottom.

Below is the transcript for the video…no need to read it if you’re going to watch the video… I just included it so some of the search engines could pick up on the keywords. ;-)



Hello Everyone. Today I’m going to show a plastic extruder system that I built. The end result was to produce a synthetic, cost effect growing medium for my Aquaponics system.

The extruder consists of a hopper for high density polyethylene pellets. An auger then forces the pellets through a dual zone heating chamber. The heated material is forced through a small die at the end of the chamber.

The temperature in each zone of the heating chamber is controlled by a Teensy AVR microcontroller which is monitored and adjusted through its USB port connected to a laptop.

The auger is driven by a windshield wiper motor and it is geared-down using an old bicycle sprocket and chain.

The hopper is filled with HDPE pellets where they are slowly forced into the heating chamber. It can also be filled with shredded milk bottles or shredded milk bottle caps to add color.

The heating chamber is covered in some fiberglass insulation to conserve heat. There are two thermal probes mounted near the middle and end which provides accurate readings to the controller as the material is heated. The heating elements draw around 16 amps at 12 volts.

The molten plastic that is extruded from the die is squeezed through a set of rollers which embed a texture into the material. A small tube blows air onto the pressed material to cool it, and to keep the rollers cool.

This is one of the rollers after I turned it on my lathe with a close-up view of the texturing.

And this is a close-up video of the material being extruded and pressed through the rollers.

Here is a close-up view of the finished material once it has been cut to length. There is a waffle pattern embedded into the plastic which provides plenty of surface area for bacterial growth. The media lies flat which helps to retain moisture during a drain cycle. The pieces have plenty of spaces between each other for water and root growth.

Most HDPE plastic is classified as food-grade. However, one problem is that nothing likes to stick to it. Even though a texture has been embossed into the plastic, a small amount of movement can disrupt anything that was clinging on it.

This is a time-lapsed video taken with my PlantCam over a 30 day period. There are 3 bean plants growing. I also planted lettuce seed which didn’t germinate, probably because the top inch of the media doesn’t retain moisture like stone or expanded clay.

After 30 days, I removed the beans from the aquaponic system. I had the net basket wrapped in foil to prevent the roots from wandering into the surrounding stone. The roots seem to have an aversion to growing in the plastic and mainly grew between the basket and foil.

Thanks for watching. If you have any questions or comments, please leave them in the comments section below. Also please subscribe to my YouTube channel to see future videos!

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Geodesic Dome Greenhouse Part 12 THE END

This is the final video about construction the aquaponic geodesic dome greenhouse. Dont worry, there are still more videos about the aquaponic system and other projects were working on!



Hi Everyone.  I’m Rob Torcellini from Bigelow Brook Farm.  This is the last video on the series on building the geodesic dome.  I wanted to thank you for watching all of these.  I’ve had a great time of the last year building this.  Learned a lot, made a few mistakes along the way, but overall, it came out pretty good!

I’m planning on do a short series of videos about how I set up the aquaponics system inside the dome.

I also had this camera shoot about 1500 photos of the entire project that will be in a time-lapsed video.

Again, thanks for watching and we’ll see you soon!


It’s starting to get a bit warm in here so it’s time to add some vents.  I started by building frames that would fit loosely inside various areas around the dome.  There will be a total of five vents and each section will be able to swing open and closed.

Next I removed the existing polycarbonate glazing and then attached the new frame to the dome with a couple of standard door hinges.  In order to get the glazing to fit back into its spot properly, I had to cut it down a bit so that it wouldn’t hit against the hinges or the surrounding polycarbonate when the vent was closed.

I simply held the polycarbonate into the new frame and screwed it into place with the washer-backed screws and the vent was done.  The remaining 4 vents installed the same way, but just a bit trickier for 2 of them since they were 15 feet off the ground.

All of the exterior joints needed to be sealed to help prevent the rain from leaking in between each joint.  I used a clear polyurethane tape which is used as a protective tape on the edge of aircraft wings and wind turbines.  If it’s good enough to hold on to a wing at 500 miles per hour in the rain, it just may be good enough on the dome.  It was easy to apply by just removing the backing and pressing it down with a j-roller.  Once it bonds with the polycarbonate, it’s basically impossible to remove.  After covering each joint I drove a washer backed screw through the tape and polycarbonate.

Wherever there is a vent opening, I applied the tape to the polycarbonate and cedar which created a channel for the water to drain from.  I’m not sure how well the tape will bond to the wood…only time will tell.

Applying the tape on the upper areas of the dome proved to be a bit trickier. I found it to be unnerving being up there with the risk of sliding over the side or dropping through a section of polycarbonate.  I’m happy to say there were no trips to the hospital for this project!

I wanted to use some of the logs that I cut down last year from the site in a couple of areas of the dome and for grow beds for the aquaponic system.  My neighbor stopped by with his WoodMeiser saw mill and milled roughly 1500 feet of white pine into 1 inch and half inch thick boards.  It was a great way to save some money instead of buying lumber and we got to use some logs that would have gone to waste.

Inside the dome I covered the walls with some of the half-inch pine boards.  Each piece is roughly fitted, measured for the proper angle, and cut to size.  Sometimes the pieces had to be cut a few times to fit properly.  It was a very tedious process cutting all the angles, but the end result looks great!

In the shed area, I only filled the walls with one inch of foam to save a little money.  The rest of the wall cavities are filled with regular fiberglass insulation.  The boards on these walls installed much quicker since there are long and have square cuts!

The ice and water shield held up well through the winter but it was time to shingle the roof.  A friend of mine volunteered his crew to help out which was much appreciated.  Even for a professional builder, there was a lot of pondering on how to lay the shingles on the dome area.

On the south side of the greenhouse, I leveled and planted timothy grass.  Eventually, this area will used as a small orchard.  A local arborist was more than happy to get rid of their wood chips so I was able to spread this on the remaining areas that didn’t have any top soil.

The shed area and dome knee-wall is sided with cedar shakes.  They require little maintenance and they help to give a contemporary building a little New England feel.  I also added a small awning over the main entrance to make the building less….boring.

That’s about it.  There will still be more videos in the future.  If you have questions or comments, please leave them in the comments section below and I’ll try to address them in future videos.  Thanks for watching!

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Adding Automatic Vent Openers

I finally get to work on some of the more exciting things in the dome.  Automation!!!  I love being lazy!




A few years ago I made up some vent openers which use windshield wiper motors. They work well for the small greenhouse, but the frames have had some structural problems in strong winds.  For the dome greenhouse I’m using linear actuators to operate the vents.  The actuators have a lot more lifting strength and can withstand stronger wind forces.

To attach the actuator to the window frame, I took a piece of angle iron and made a cross brace.  The brace will fit about half-way up the vent.  I cut off a section from each end so that there were tabs that would be used for bolting the brace into the face of the vent frame.  I then welded a couple of tabs into the bracket which provided the connection linkage for the actuator.  After rounding over the edges and cleaning up some of the welds, the bracket was attached to the vent frame.

The rest of the braces are standard steel bar stock that are bent at slight angles.  There are four of them which go from the greenhouse struts to the back side of the actuator.  Because of the odd angles of the dome, a few of braces need to be bent as compound angles.  If this was a traditional vent the angles would have been much simpler bends.

I temporarily bolt the top brackets to the back side of the actuator and mark where the brackets connect into the dome’s strut.  It wasn’t necessary, but I set the actuator to be level when it was closed, simply for aesthetics.  I drilled out the first hole in the dome strut and attached the bracket.  Once the pieces start to hold themselves in place, it’s much easier to mark and attach the remaining brackets.

The bottom brackets are marked and installed the same way.  It’s just a bit more critical to make sure they are placed properly so that the vent is pulled completely closed when the actuator is fully retracted.  Once all four brackets are secured, the pyramid shape from the triangulation creates a sturdy mount for the actuator.

Now that it’s fully assembled, a quick test is in order.  All the pieces are cleaned and painted to give the system a nice new look!  Once the paint is dried, it’s a quick reassembly and then time to it get wired to the controller.

A regular two-conductor wire is used for each actuator and each vent opener has a line that runs back to the controller.  The actuators have built in limit switches which stop the motors automatically.  To open and close the vent, you just have to reverse the polarity of the power in the wire.

The thermostat controller is a prototype six-relay control unit that can be programmed to set each vent to open on independent temperatures.  The unit can be programmed to sample the temperature at predetermined intervals and also delay the change between relays so that all the vent motors aren’t running at the same time.  This keeps the unit from drawing too much power all at once.  Each relay can also be disabled and forced into an open or closed position.  There are more details about the thermostat in the description area of this video.

Thanks for watching.  Don’t forget to “thumbs up” this video if you want to see more like it in the future and feel free to leave comments too.

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