Cut on a Hot Tin Roof

Enlarge Image Image Gallery CLOCKWISE FROM LEFT. The windowbox planter that started it all . . . . This greenhouse produces flowers and vegetables right through the long winter .... In warmer months, the skylight opens to provide ventilation.

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My wife, Terri, and I—enthusiastic gardeners both—had long dreamed of building a solar greenhouse that would enable us to garden right through Illinois's long winter months. Unfortunately, our limited budget kept that dream just a dream . . . until we stumbled on a low-cost way to overcome our budget crunch and grow fresh vegetables, herbs, and flowers year-round: We converted one of those ubiquitous prefabricated metal storage sheds into a compact but highly productive solar greenhouse.

ROOTS

The seed of inspiration that would eventually grow to become our greenhouse took root the day I constructed a window-box planter from 2 X 2 redwood strips and 1/4"-thick polycarbonate sheeting. Mounted on the outside of a south-facing, double-hung window, this minigreenhouse added heat to the interior of our home on sunny winter days, while the plants growing in the box were in turn warmed by the house at night.

It was a grand arrangement. But we eventually moved to a house in which none of the windows were the right size to accept the box. Consequently, the window planter became a decoration (Terri had a different word for it) in our new backyard. Then one day a friend gave us a 10' X 9' metal storage shed—spanking new, unassembled, and still in its crate. As we were trying to decide where in the backyard to erect the shed, I noticed the old window box lying fallow nearby, put one and one together, and conceived the idea of converting the storage shed into a solar greenhouse.

GETTING THE PROJECT OFF THE GROUND

As soon as we had a set of plans committed to paper, we began construction by excavating a 2'-deep foundation trench a little larger than the exterior dimensions of the storage shed. After pounding four preservative—treated 4 X 4 posts into the ground-one at each corner of the trench—we connected their leveled tops with treated 2 X 6 planks to form a foundation for the shed's metal base and then added a special ledge to support the window box, which would project from the south-facing wall. (We went with 2 X 6 rather than 2 X 4 foundation sills to provide enough wood, after the shed's base was bolted in place, on which to rest the interior walls.)

We enclosed the foundation's sides by gluing rigid sheets of 2"-thick expanded styrene insulation vertically to the outsides of the foundation frame. And to help keep out insects and rodents, we covered the insulation panels with aluminum screening. That accomplished, we bolted the base of the unassembled shed to the frame, then filled in the excavation around the foundation.

Terri and I assembled the metal shed according to the manufacturer's instructions . . . except that we didn't install the south or all of the west wall panels, or the sliding doors. And since the finished greenhouse would be charged with the task of holding its interior heat against the tug of winter's cold, we took the precaution of laying a heavy bead of caulking compound along each of the seams before screwing and bolting the pieces together.

The next step was to frame in the interior walls—both for added strength and to provide double walls between which we could sandwich insulation. We used treated 2 X 4 studs to prefabricate frames for the south and west walls (which were to be covered with solar glazing), but opted to save a few bucks by framing in the metal-paneled walls with economy studs. (We located the upright studs to correspond with the vertical seams in the metal paneling, then glued wood to metal from the inside and drove aluminum nails through the metal and into the studs from the outside.)

Since the metal roof support framing included in the shed kit appeared to be less than substantial (a crushed roof is the most com mon way a metal storage shed meets its end in snow country), we bolted a 2 X 4 to the bottom side of the center ceiling beam to increase the roof's rigidity and load-bearing capacity. Finally, we completed the stud work by framing in a 2' X 4' area of the roof to accept a homemade skylight.

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