Clearly Superior

We were not entirely sure that we would get around to it this fall, but we recently completed the replacement of our clear polycarbonate hoop-shaped greenhouse with a better built, glass-glazed greenhouse. We were getting worried about the old glazing since it was getting more stress cracks around the fasteners, but the polycarbonate hadn’t yet yellowed after 11 years of use.

If you compare it with the old design seen here,

it is no longer hoop-shaped, now having a peaked roof, operable indoor vents at the peak of that roof, and taller doors. It has roughly the same footprint of the older model but we removed the insulated pit on the north side and added to the height of the concrete block retaining wall. We had built an 8′ by 3.5′, “twinwall” polycarbonate cold frame last year and we have used that in the northern half of the new greenhouse to help protect plants being overwintered. The glass panels that make the south wall are 3 foot wide, single-glazed doors purchased from a local building recycling center for $3 each.

Both the front and rear now have rain collection troughs to send water into a mostly-buried 55-gallon polyethylene barrel so we always have a ready water supply during the active growing season. And the steel roof on the north side has both a layer of “reflectix” (bubble-foil) insulation under it as well as an interior layer of recycled “kalwall” (glass fiber-reinforced polyester) over the red cedar, 2-by-4 inch, roof joists. And to help protect the angled glass from summer hailstorms, we recycled the old steel “cattle-panel” fence sections, that once helped support the old greenhouse’s polycarbonate sheets, into “sandwiched” panels of steel panels with aluminum window screening between them. They also help to shade plants in the summer since the screens cut solar gain by about 50%.

It may not be bigger or better insulated, but we have found that this size works well enough for us and it fits the space we have. And using acrylic blankets over the plants during cold winter nights has kept cold-hardy vegetation alive even during last year’s repeated bouts of -25 F. This one is just more sturdy, more wind resistant, less “drippy” from the ceiling, more rot-resistant, and easier to access. We look forward to another winter of fresh greens!


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