Geodesic Dome Greenhouse - Part 9 - Polycarbonate!
Here’s the latest in the dome greenhouse series showing the polycarbonate installation. It’s nice having it enclosed and not working out of the wind. It’s still cold, but the heating system is next on the list!
Here's the transcript for your reading pleasure! ;-)
This video will show how the exterior of the dome is covered. The northern face of the dome has no polycarbonate and is covered in OSB and will eventually be shingled. Each of the triangle sections needs to have studs added to support the boards. Placing them can be tricky when it’s difficult to reach all the points.
Sometimes the best laid plans don’t always work…
Once all the studs are installed, it’s time to install the OSB. I found it was easier to set the sheathing by ripping the OSB into two foot strips instead of leaving them 4 feet wide. It also reduced the amount of scrap that was generated.
The shed roof and part of the dome are covered in water and ice shield. This will protect the building during the winter and will allow me to shingle the roof in warmer weather. The shielding has an adhesive backing which helps to hold it down to the OSB and a few roofing nails insures a gust of wind won’t peel it off.
The polycarbonate sheets are 6 by 24 feet long. I set up a couple of sacrificial sheets of OSB on the ground as a cutting area.
I decided to repurpose an old tape measure and cut it up so I could easily measure out the various leg lengths for the triangles. With a couple of clamps to hold the ends, it made it easy to triangulate all the points. I found it was easier to make my marks by just poking a nail through the material. Trying to mark the frozen poly with a frozen Sharpie was a futile effort.
The polycarbonate cuts very easily with a sharp circular saw. After I filmed this, I discovered it was even easier if I placed another scrap piece of polycarbonate under it so the blade didn’t have to also cut into the OSB.
Setting up a guide allows for a nice straight cut. After each piece is cut, the protective film can be removed and the sawdust in the flutes is blown out with compressed air.
Installing the panels was quite simple providing there was no wind. Before cutting each panel, I did measure each opening to insure the measurements matched the computer calculations. There were a couple of sections that were slightly off which was probably from slight errors in the hub construction or the strut measurements. But, for the most part they all went in as planned.
Each panel was cut so that the flutes are orientated to allow for condensation to drain out.
Once I got down to the ground level, it was even easier to install each section. All the panels are held in place with stainless steel screws that have a neoprene-backed washer. The screws pierce right through the polycarbonate and the washer creates a watertight seal against it.
All the joints will be taped in the spring since the waterproof tape needs to be applied when it’s over 60 degrees. During this filming it was 20 out. You may have noticed that I’m wearing insulated boots, long-johns, a sweatshirt, insulated hoodie sweatshirt, scarf, winter coat, winter hat under the hoodie, and insulated gloves!
All the panels intersect nicely over the hubs. The original plan of rabbiting each stud so that the panels wouldn’t interfere with the bolts worked out well. Also adding the bevel to the studs made a large flat surface for the panel to rest against.
The panels along the base are cut extra-long so that they will hang over the knee wall. This will help to shed water and prevent it from getting into the dome through the knee wall. The overlapping pieces are simply cut off with a razor knife.
The northern face of the dome that isn’t covered by the shed was also studded and covered with OSB. Unfortunately, my HD camera was broken so I wasn’t able to film this part, but this is what the final construction looked like.
When I laid out the building, I oriented it so it faced due-south. It now acts like a huge sundial and it’s very easy to tell when it’s time for lunch!
That’s it for now. Next up may be the heating system. It’s getting difficult to work in the freezing temperatures! Don’t forget to join our Facebook page!
This phenomenon is called “needle ice” and it occurs when the soil temperature is above freezing and the air goes below freezing. The water in the soil is drawn out by the cold air and quickly freezes, building these long strands of ice. They’re also fun to crush!