Thursday, June 16, 2011

End game in Greenhouse 2.0

In our last thrilling episode our greenhouse had the top cover on it. It is held down by a couple of logs and some stones in strategic locations. I want the coverings to come off easily, you see. That way, come fall, I can dismantle all but the frame if I want to do that. But we now have to enclose the ends. The ends are an uncomfortable arch shape. Offhand I cannot see an easy way to do this. So the idea was to build framing, then resort to my tried and not-so-true system: duct tape and staples. The duct tape keeps the staples from tearing out. Ok, the frame, not so difficult.
You are looking front to back. The front is of course different from the back. It needs a door. Got to get inside the greenhouse somehow. The verticals are all buried in holes. Horizontals are lashed. Not one piece of metal so far. The next step is to staple on the coverings. I reused the coverings from the old greenhouse, willy-nilly. On the back we have...
...duct tape to hold the staples -- otherwise they tend to tear out under wind stress. The still tear out. Too bad. Duct tape is cheap. So are staples. On the front we have a different system:
There is a "curtain" hanging from the center. That acts as a door. We need to get inside the greenhouse, of course. Not too elegant but it works. So I took my trusty remote thermometer and hung it in the greenhouse. I am truly amazed. This lashup (literally) is far better than my old greenhouse. With just a little sun it is about 5C better than outside temperature. With more sun it goes up to 10-15C better than ambient. I am stil trying to figure out why this is so. Greenhouses, contrary to popular belief, do not work because of the difference between visible and IR transmission. I will have more to say on this subject later. They work because they control convection. So there is something about the convection pattern in this greenhouse that makes it efficient. I will say something about this when I have it figured out. Meanwhile I transplanted tomatoes and zucchini in the GH. These guys are a bit shocked but seem to be recovering. Tense times. But perhaps this thing is really better than what I had before.

I am really sold on lashing for Alaska construction. Lashings give and take. Nails do not. And this greenhouse cost only the 6-mil visqueeen covering. I think I paid about $25 for the big roll. I used it for several previous incarnations of the greenhouse and there is still some left. And it was put together by one person with no mechanical aids, unless you count rope. I spent about $20 for rope. All in all, not a bad price.

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