At this meeting we got our greenhouse much nearer to completion— the plastic cover is now in place. We pulled it over the frame, and then rolled the edges around some scrap metal pipes, which were buried in shallow trenches along the sides. This should help to keep the plastic in the ground. We then cut short sections of black plastic pipe, slit them down one side, and used them to clamp the plastic to the end hoops. (Here is a link on an earlier page, where it describes the first phase of the greenhouse construction. Greenhouse construction )
Here are some pictures of the greenhouse.
We still have to tighten the plastic a little, and put some duct tape under each clamp to stop them from abrading the cover. Then we have to modify and place a door, and attach it to the frame. We left the plastic cover loose at the west end, so that the door can be put into place. We will then attach the plastic tightly to the west end hoop. (Right now it is weighed down with landscape timbers.) We also have to frame a vent and attach an automatic vent opener, insulate the north, east, and west sides with bubble wrap, and pile a little more earth around the edges. After that, we can begin to instal hot frames and thermal mass.
The thermal mass will be large, black containers full of water. This will act as a sort of flywheel, absorbing the extremely high temperatures during the day, and releasing the extra heat at night to keep the greenhouse warm. Without any mass, the greenhouse would cook plants during the day, but rapidly freeze at night if the outside temperatures are much below thirty-two degrees.
The hot frames will be a second translucent structure inside the greenhouse. They will be sunk below ground level and insulated. Since they will only be exposed to the moderated conditions inside of the greenhouse, they will keep a fairly stable temperature. Extra heating will be provided inside the frames by means of compost and or electricity. For low cost electric backup heating, we could use an infrared bulb or a heat cable. These would be set to come on only if the temperature dropped dangerously. The hot frames will be used to start seedlings in the spring.
We also discussed remodeling the run in horse shed on the property to store tools and equipment, and our mason bee project. The shed remodel will probably be our next project.
At this meeting we got the frame of our Greenhouse put up. We bent inserted lengths of rebar into PVC pipe, and bent the rods into hoops, inserted about a foot into the ground. We then joined them at the top with another length of PVC/ rebar. The rebar provides the strength, and the PVC keeps the rebar from abrading the plastic cover.
Due to the wind, which picked up towards the end of our meeting, we were unable to get the plastic cover attached. It would have been buried along the sides of the greenhouse. We also need to build a wooden frame at one end to contain a door and vent. Once we get this done, we will install an inner hot bed for starting seedlings, low tech insulation on the north side, mass to collect solar heat and even out temperature swings, and possibly a compost heating system. These systems will be backed up by an electric heater.