Growing Spaces Geodesic Dome Greenhouses
Filed Under: Green Technology, Organic Gardening on September 23, 2009
I really want to build a greenhouse in our yard. I have the space, I know what I want it for, but I can’t afford all the money required to get all that glass and put together all of the stuff you need to build a solid greenhouse. I could use heavy-mil plastic instead, but that has to be replaced every couple of years. I’ve been collecting windows and doors with windows in them on town garbage days, but at this rate, it will be a dozen years before I have enough to build a greenhouse.
Worse yet, we get hail in this part of the country. That glass wouldn’t stand a chance.
This weekend at the Rocky Mountain Sustainable Living Fair, I saw something that made me salivate with need. Nope, it wasn’t a new burrito or a girl in skimpy clothing. It was a geodesic dome greenhouse. Turns out, it was from Growing Spaces, a company right there in Colorado and not too far from my own house!
I mentioned them earlier this week when I wrote about Global Children’s Gardens. This is the company that GCG gets their greenhouses from (or, more to the point, who donates them). At the Fair, I had the chance to step inside a dome and eyeball its features, construction, and some of its components. I also met Udgar Parsons who, to his credit, was more interested in talking to me about the children’s charity than he was the domes.
Not much of a salesman, but a guy with a great heart. He did explain a few things when I pressed, however (and after we’d promised to visit the charity booth next to the greenhouse). The smallest of the dome kits (what he had there) is about twelve feet in diameter and stands about 8 and a half feet at its center. Because of the shape of the geodesic, though, the slope is gradual and nearly all of the inside allows most people to stand up straight. Even me, and I’m six foot three inches.
The basic framework is 2×4 boards cut to length to make triangles. The meeting point of each triangle has a metal plate through which bolts tie the corners together to form each intercept. The basic frame can be put up by two people working together, without any experience, in about a day.
The covering is a double-glazed polycarbonate made to have air channels at center. These channels act as an insulator and keep any frost buildup on the outside form penetrating inside. The stuff is also tough, somewhat elastic, and resistant to impact from hail, heavy rains, etc. It can also bear a sizeable snow load. Each triangle is about three feet to the side (my estimate).
These panels allow 65-85% of light transmission through them into the greenhouse. That compares to about 90% with most glass that is double-paned and coated for strength, like you would find in a glass greenhouse. The poly panels are much more insulative, however. These panels take less than a day for those two people with no experience to put on the dome. The poly and glazing have a 10 year warranty against sun and hail damage.
The north side of the greenhouse is insulated with simple sheeting that reflects light on the inside (increasing the inside lighting) and keeps the cold from sucking heat from the greenhouse. This is also where the integrated water tank for the greenhouse is located, allowing for both heat retention and cooling, since the water volume takes a while to heat up and cool down compared to the air in the greenhouse.
This water is also heats air that blows through piping around the greenhouse under the plants, beneath their soil. This keeps them warm for longer periods of the year, maximizing the growing season. This takes a couple of hours to set up and requires only a garden hose to fill. The air is circulated by a fan powered by a solar panel which can optionally include a car battery for power storage overnight.
Another cool feature are the windows, which are on pistons filled with a gel that automatically expands and contracts in reaction to heat. So when the gel heats up, the piston expands, opening the window to vent the heat out. When it cools, it contracts, closing the window again. These are fully automated in this way, without need of electricity or thermostats, and open the windows just enough to do the job.
The foundation walls of the greenhouse are heavily insulated, keeping it off the ground and keeping the weather out. The door is similarly insulated with thick foam and both are made from pressure-treated lumber. These are also termite-proofted. The same insulation is in panels that are buried under the soil around the greenhouse’s foundation to prevent frost from creeping under the greenhouse.
All in all, these are a really cool, local design that have been thoroughly world-tested. Plus, Udgar’s business card came in a little baggie with some pea seeds and growing instructions. Maybe he is a good salesman after all.
I have dreams of putting one of these in the yard and moving my office in there to be in the middle of the plants.
