Since moving back to the city, I made the decision that the greenhouse would be closed up during the summer months. We felt it was important to cover the greenhouse to minimize the amount of heat gain and to protect the polycarbonate.
Although it is entirely feasible to run the greenhouse during the summer (I did so with my last greenhouse), the new garden design in the backyard centers entirely on food production and it would have been to much for me to keep up with the garden during its peak growing season and keeping the greenhouse running. Enter the decision to close the greenhouse for five months out of the year.
It is a lean-to greenhouse and with it being connected to the house, minimizing the amount of heat gain inside the greenhouse became a priority. We made a greenhouse cover to solve the heat issue and to also protect the polycarbonate. Polycarbonate does yellow over time, so the cover will help mitigate that issue as well.
Being that I live in the desert, I opted to make my cover from inexpensive painters’ drop cloths. Rainfall is not a big concern in these parts and the cloth would hold up better that tarpaulin with the intense summer sun. A greenhouse in a wetter climate would benefit more from a cover made of tarpaulin because a wet greenhouse cover made from cloth that does not shed water would be extremely heavy. I purchased drop cloths inexpensively from a local discount tool store and also picked up a bag of grommets. The bag of grommets even came with a grommet setter.
Using my sewing machine, I sewed the drop clothes together into panels large enough to cover each side and the top of the greenhouse. We measured each side (adding a half inch to each cut edge to account for seam allowance) and then transposed those measurements onto the cloth panels. I cut out the panels and sewed them together. We set grommets on the outside edges of the cover, and then placed (or rather wrangled) it over the greenhouse. We pulled it tight and then hooked the grommets over screws we put in the greenhouse frame.
Although this was not the easiest greenhouse project I have done, with a little help I was able to finish it in a day. When it comes time to open the greenhouse in October, the cover will fold up nicely for storage in the shed during the colder months.