Intensive Gardening: Using Solar Energy to Increase Harvests

You can double your garden's yields, yet use less space by assembling solar panels to warm the crops. Includes diagrams, background, indigenous solutions, solar appliances, open beds, layout and size.
By Leandre Poisson and Gretchen Vogel Poisson
February/March 1995

The intensive, open bed design, with drop frames placed around individual plantings, minimized the wasted space of traditional rows.
MOTHER EARTH NEWS STAFF
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When we began homesteading, one of the hardest things we had to do was to change the habits we had developed in our consumer lifestyle. Our question changed from what do we want for dinner to what do we have for dinner. We must confess that, toward the end of our first winter, our enthusiasm waned when the answer continued to be “root crops.” We wanted to develop a gardening system that would enable us to have the food we like—fresh produce available throughout the year. Today, having enough of the kinds of food we really like to eat is a concept that has become thoroughly ingrained in our self-reliant lifestyle. We have gotten into the habit of having what we like—fresh, great-tasting, healthy food—because we now possess the necessary skills and tools to be truly self-reliant.

Intensive Gardening

When we first decided to homestead at the end of the 1960s, Lea's motivation was primarily intellectual, while mine was purely instinctive. I was raised in the country, in a family that grew the bulk of its own foodstuffs. Fate must have smiled on Lea when he bought our property, because almost every bit of it sloped southward, making it ideal for both solar living and gardening. It had been a working farm less than one hundred years before, though by the time we moved there it had long since reverted to forest.

Lea cut the large second-growth pine trees that inhabited the site where we decided to locate the garden. A neighbor pulled out the stumps with his back-hoe. By the time he finished, the ground that remained was a mixture of hardpan and rocks, with a pH of 4.5 and no humus or any other suggestion of fertility. We began to build up our soil organically by adding hundreds of pounds of rock minerals and by raking up leaves and topping them with mulch hay to keep them from blowing away.

That first spring of 1970, when it came time to plant, we laid out our garden in traditional rows, since that was all we knew how to do—all except for the potatoes. We decided to plant the potatoes in the way a local friend described. Fairly late in the spring, we cut up five pounds of supermarket potatoes and planted them on top of the soil in a six-by-10-foot area and covered them with rotted mulch hay. As the plants grew, we settled more hay around them. When we harvested in the fall, that little patch yielded 70 pounds of potatoes. We recognized that something special had happened in our potato patch. It was our first intensive bed.

The next year we shaped random, free-form beds and planted vegetables in clusters rather than in rows—a method of planting Lea had observed in France in the 1950s. Then we noticed something strange. We had planted the same amount of vegetables as in the previous year, but in only a little over half the garden space. We began looking for different things to grow, branched out into mangels (sugar beets) for our pigs, and started planning crops of soy and other dried beans and flint corn for the following year. This was our first experience with an intensive gardening system.

Indigenous Solutions

Meantime, we had started an association of homesteaders in our county. At one of our meetings someone brought in a film about organic gardening in Japan. One scene showed a farmer walking along a high, mounded bed on a board and then reaching down to pull out (with some effort) a diakon radish the size of a baseball bat. That one image in the film impressed itself indelibly on our minds.

We began to research how indigenous peoples fed themselves, both historically and in the present. Indigenous solutions evolve when people live in one place over a long period of time, working with an area's resources and limitations to provide shelter, food, fuel, clothing, and transportation. We discovered that most preindustrial indigenous growing systems consisted of mounds, terraces, or beds. Gardening in rows is a relatively recent phenomenon, closely linked to the rise of mechanized agriculture. Clearly, intensive agriculture was not a new fad but an ancient and efficient method of growing crops in many climates and cultures.

The following year we converted our garden into 18 five-by-50-foot raised beds. We made the beds 50 feet long because that distance represented half of the garden's length. Four feet seemed to be the most useful width because we could easily reach the middle of the bed from either side. The beds were two feet apart from crown to crown and the paths between the beds were one foot wide. An opened newspaper fit exactly from edge to edge and two flakes of mulch hay placed side by side perfectly covered the newspaper.

At first our idea of bed building involved simply adding humus material and fluffing the beds into shape. Then it became obvious that if we took the useful dirt from the pathways and piled it onto the beds, we could raise the beds by lowering the pathways and make use of every bit of our valuable soil. That fall we began to experiment with crude seasonal extenders made by surrounding part of a bed with hay bales and stretching polyethylene sheeting across the top of the bales.

We left several of these seasonal extenders in place and the next spring we got a jump on planting peas and members of the cabbage family. We began to mulch carrots, beets, turnips, and parsnips for midwinter harvest and discovered that carrots and parsnips kept growing underneath the snow. Attention was soon directed toward our unusual garden, and even the county extension agent dropped by to see what we were up to.

In 1974, we built permanent wooden sides for our raised beds. These board-sided beds concentrated the humus-building material we added to the garden, prevented rainwater from running off the beds, and kept the sides neat. We had already been edging and mulching the dirt-sided beds, but the boards were more effective.

Lea was working at the time as a consultant to the Kalwall Corporation, a manufacturer of building products. At Lea's urging, Kalwall developed a solar-friendly, fiberglass-reinforced plastic sheet glazing material that he dubbed Sunlite. This Sunlite material was dramatically lighter than glass per square foot, and it turned out to have many applications for Lea's designs and for the solar industry as a whole.

Lea began thinking about how to build the smallest and simplest solar greenhouse possible. Standard freestanding greenhouses provide no net energy gain when the net energy of the food produced is compared to the cost of heating the unit in wintertime. Add-on solar greenhouses or sun spaces create an energy deficit when you compare the amount of food produced in them to the resources and energy used in their construction.

In 1976 Lea conceived of a gardening device that met all of his design requirements: it was inexpensive, easy to build, and used resources and energy wisely. We christened this device the Solar Pod. That fall we prepared a bed and planted it with lettuce, but we didn't place the Pod on the bed until February. When we shoveled off the snow and uncovered the bed, which we had protected with a scrap of fiberglass, to our surprise the lettuce still looked green and edible underneath all that snow.

After we set the Pod in place, we were amazed by how the soil under it heated up and how the lettuce grew...and grew, and grew. It was quite possibly the most photographed lettuce in history. Friends came to see the experiment, and they mentioned to us that the Pod reminded them of intensive gardens in France. The following winter we discovered several books on French intensive gardening, or what the French call the Marais system.

Marais practitioners placed bell-shaped glass jars, or cloches, over individual plants or groups of seedlings to provide heat and protection and to create a microclimate underneath the glass. They also used extended cloches, which looked like what we would call cold frames. The cloches were used to preheat soil for planting and to cover seedlings and small plants; the glass- topped frames were set over plants that would be grown to maturity. In cold weather, woven straw mats placed over the glass at night provided a limited amount of insulation.

Solar Appliances

During the 1970s we lectured extensively all over New England on passive solar use and on our gardening methods. At that time we thought of our system as a translation of French intensive methods. We had replaced the heat-assisting methods of fermenting manure, glass-topped frames, and straw mats with our passive solar Pods constructed with modern materials. The improved heating function of our double-glazed, insulated devices, which trap sunlight and make its radiant heat available to plants even in the dead of winter, proved to be better and more versatile than traditional glass frames and cloches, which don't work in our cold climate because of their relatively poor insulation value.

Inspired by the concept of the original cloche, Lea set to work in an attempt to bring these, too, into the late twentieth century. Glass cloches had all the disadvantages one would expect with glass. They were heavy (weighing about 5½ pounds apiece), hard to move around, and expensive even in their heyday. They had to be whitewashed to prevent the so-called lens effect of clear glass, which would focus the sun's direct rays and burn plants under the glass. And cloches had to be opened and closed every day.

Lea wanted to make a cloche from a flat sheet of Sunlite that would create a simple, protective environment for growing plants. He also wanted to provide an alternative to the short-lived, throwaway products like "hot caps" already on the market. The shape that made the most sense was the cone, but Lea found he couldn't close the material completely at the top without cracking it. He decided to leave the hole on top, figuring it would be easy to plug with mulch hay or cap with a circle of glazing material if necessary to prevent heat loss.

Lea experimented with many different cone profiles and found that steeper cones acted like chimneys, while the structure of flatter ones wasn't strong enough. The best and final configuration, coincidentally or not, resembles the profile of the great pyramids. We christened this lightweight modern cloche the Solar Cone.

With the previously unwanted hole on top and its base settled into the ground, the Cone acted as if it were a terrarium. The solar heating inside the Cone accelerated the transpiration rate of plants, which in turn accelerated their growth rate. The Cone's sloped sides recaptured moisture as condensation, which rolled down the sides and returned to the plants. The hole on the top permitted the necessary gas exchange of carbon dioxide and oxygen, but inside each cone the environment resembled a miniature rain forest. As long as the ground remained moist and the Cone was set firmly, plants would not wilt, no matter how hot it got inside.

In all of our experimentation with Cones and Pods, we kept in mind that these solar appliances had to work thermally, had to be simple to build and maintain, and had to be well within the economical reach of the average gardener. We designed the appliances to make the most of the building materials used (plywood, glazing, insulation), with as little waste as possible. In turn, the assembled appliances optimize growing conditions in any climate—from far north to deep south—and provide functions as varied as heating and shading, as well as wind and insect protection. The multiple functions and portability of the appliances encourage gardeners to use them creatively and move them around the garden as needed.

As we distilled and further refined our gardening system over the next decade, we began to realize that we were no longer translating the French system to America. We were in the process of developing our own unique system—a simple, state-of-the-art, flexible, and continuously productive method of growing food on very little land—which we named "American intensive gardening."

We define "American intensive gardening" as a continuous food producing system, one that provides an ideal growing environment for the entire plant. By creating and maintaining a deep, well-balanced, fertile soil, the system optimizes growing conditions below the ground. By using heat-assisting devices to create beneficial microclimates for seedlings and mature plants, it ensures optimum growing conditions above the ground.

Open Beds

Everything in life has its pluses and minuses. In our second decade of gardening, the minuses associated with raised beds started to outweigh the pluses. We began keeping track of how much time we spent landscaping the beds: edging, siding, mulching, and smoothing and evening them after adding horse manure. We spent some 20 or 30 hours a season just mulching the rows between beds.

Sure, the beds looked great, but was all this landscaping work really necessary for food production? Also, since our goal was to not step on the garden soil, tasks like trellising became awkward with the raised beds. Maybe we were just getting older and lazier, but we decided we needed another system, one that would be easier, simpler, and better than raised-bed gardening.

Another factor that changed the way we wanted to garden was the flexibility of our solar appliances. Since moving plants always sets them back, no matter how carefully they're transplanted, it made more sense to move the appliances than to move the plants. More and more we found ourselves planting beds of vegetables in formations that could accommodate the appliances we would later set over them.

We also kept exploring new ways to use the appliances in different seasons, with definite goals in mind: First, we wanted to create a gardening system that would give us greater flexibility than our four-foot by 50-foot raised beds, which were locked up in a military-like formation. Second, we wanted to grow more in less space.

We realized we needed portable bases we could easily place over crops when they needed Pod protection. So Lea built six simple four-by-eight-foot rectangular bases out of pressure-treated two-by-six-inch boards to go under the Pods. We called the bases "drop frames."

These simple, humble devices became the catalyst for a whole new way of thinking about bed gardening.

The drop frames proved to be inexpensive to build and easy to move around. They represented an immediate and obvious improvement over our network of permanent board-sided raised beds. Used by themselves, the drop frames were wonderful to sit on while planting or weeding, especially with a board set over the top that could slide along, making a most comfortable seating arrangement. Two or three drop frames could be piled on top of each other to provide quick wind protection for seedlings. With screening or netting set over the drop frames, insects and birds could not damage the crops. What we loved most about them was the way in which the frames defined planting areas into standard four-by-eight-foot or (placing two side by side) eight-by-eight-foot beds.

In 1979 we started an experimental and demonstration garden that measured 40 by 40 feet. Instead of building several raised beds, we made the entire surface a raised bed. Instead of limiting growing areas to strips of beds, the whole garden became a potential growing space. When needed, eight-inch-wide boards provided temporary pathways between planted areas. The growing areas could be any length or width needed. Trellising plants became more of an aesthetic option than an awkward dilemma. We planted most of the garden in the basic four-by-eight-foot areas to accommodate our standard appliances.

Since the whole garden was now open for cultivation, we called this new system "open-bed gardening." Our old raised beds had eliminated some of the wasted space we had when gardening in conventional rows, but with the open-bed approach we found we could grow on virtually the entire surface of the garden. In the fall, we could top the whole surface with horse manure and rototill the entire garden. That constituted most of the landscaping needed for the year. If we got started early in the spring, we did a shallow tilling to turn under annual weeds. Then we set up our trellises, dropped our frames and boards to use as walkways, placed the Cones or Pods over the beds, and away we'd go into the main growing season.

This new system was a piece of cake! We happily decided that in our older age we weren't getting lazier, just smarter. And we were achieving our goal of growing more food with less work and less space.

Layout and Size

American intensive gardening will accommodate almost any gardener's goals. Different gardeners can achieve different objectives simply because, within the framework of the system, there are so many possibilities as to when and where a particular crop can be grown. Since you can lay out an open bed into any configuration of intensively planted crops, the system offers flexibility.

Setting down drop frames is the easiest way to define individual growing areas. If you place two drop frames on the ground, 4 feet apart, they will define three separate 4-by-8-foot growing areas. Another way to define individual growing areas or beds is with boards that are at least 8 inches wide and 8 feet long. Laying down these boards creates temporary pathways between growing areas. We call these movable wooden paths "boardwalks." In addition to delineating bed size, they give us access to all parts of the open-bed garden, spreading out our weight as we step on them and reducing soil compaction. Using boardwalks, we can divide the open bed into growing areas of any size.

Yet another method for determining the layout of growing areas within the garden involves the various solar appliances. For example, we use the Solar Cones as a germination aid to start our climbing peas and beans early in the season. Growing areas for these crops must then be 3 feet wide to allow for the width of the Cones. If we plan to use the Cones over growing plants for frost or insect protection, we plant or transplant the crop into a corresponding configuration. For example, we space our eggplant seedlings in the spring so we can set the Cones over them in early fall to provide frost protection.

The most important determining factor for figuring the size of growing areas is the amount of vegetables you plan to grow. Compare the quantity of a particular vegetable you want to harvest with the yield information in the accompanying Storage Harvest Yield Chart bellow, then calculate the size of growing areas for various crops based on this information.

If you're starting from scratch, we recommend a ballpark size of 200 square feet (one l0-by-20-foot bed) per person. We feel this garden is the ideal size in which to learn and practice the American intensive system. To maximize yields in this modest-sized area, you would need to plant intensively and use the appropriate solar appliances to ensure a continuous capacity. As your gardening skills increase, the size of your open bed will grow proportionally.

If you're a supplemental gardener engaged in improving and augmenting your family's diet, you can easily meet the fresh harvest needs of a family of four on a 20-by-40-foot garden area. If, on the other hand, your goal is to provide food self-reliance, your garden area will need to be at least 40 by 40 feet and will require additional growing space for major staple and storage crops like potatoes, dried beans, winter squash, fruits, and grains.

If you are a reasonably skilled row gardener, by converting to an open-bed American intensive system, you can easily quadruple the yield of your growing area. One reason for this major increase in productivity is that, in the transition to an open bed, some 90 percent or more of the pathway space in the conventional row garden is converted to growing space for vegetables. By using solar appliances, you can grow more food in succession crops and, inside the appliances, vegetables are continuously producing, easily doubling yields.

We recommend that you convert your existing growing areas to open beds one section at a time. The beds can be any comfortable square or rectangular size. Access pathways can segment larger areas within the open bed. These access paths are necessary in a larger garden for delivering humus-building materials to the growing area. One way to make access pathways is by laying down cardboard or several sheets of newspaper covered with mulch hay or straw. These materials will decompose and can later be turned into the soil.

The smaller you make each open bed area within your garden, the greater the percentage of space that will be devoted to access pathways and the smaller the area that will be available for growing. For example, an existing 60-by-60-foot garden would divide most space-efficiently into four 28-square-foot open beds, with a four-foot access pathway crisscrossing the garden. A smaller existing garden measuring, say, 20 by 50 feet would most easily be divided in half by one four-foot-wide pathway, creating two 20-by-23-foot open beds.

If you are already producing the amount of food you desire or need in an existing garden, you can downsize the garden when you convert to the American intensive system. Figure on producing the same yield as from a conventional row garden on roughly one quarter of the area. A raised-bed garden's yield can be produced in an open bed of roughly half the size. By freeing up existing garden space, you can plant green manure crops to increase soil fertility on the portion of the garden not raising vegetables, you can rotate growing areas from year to year, or you can plant new crops such as small fruits or grains in the found garden space.

The materials for the Solar Cone amount to about $25, the Pod's approximately double that. The cost of a drop frame can be anything from nothing if you have some scrap lumber to $25. Properly constructed and maintained, each solar appliance has an estimated life of 25 years or more. Our older Solar Cones, which we have left in the garden through frigid winters and blazing hot summers, are still as useful as they were some 15 years ago when we first constructed them.

We use American intensive gardening techniques to grow food year around, even in our relatively cold New Hampshire climate. Our system works well on a small, personal scale, but market gardeners can also use it to grow fresh produce for local markets. Our system guarantees high returns for any labor invested in it, because it simplifies cultural care of plants by growing them in ideal conditions and in concentrated groupings, and because it spreads out garden work over the entire year, rather than cramming work into a "normal" growing season. The system requires smaller and easier outputs of labor, making gardening more of an enjoyment than a chore.

RESOURCES:

Solar Gardening by Leandre Poisson and Gretchen Vogel Poisson, from which the above was adapted, is an all-in-one guide to American intensive gardening. The comprehensive guidebook is published by Chelsea Green Publishing Co., P.O. Box 428, White River Junction, VT 05001, 1-800-639-4099.

Kits for Solar Pods, Solar Cones, and other appliances are available from Solar Survival, P.O. Box 250, Harrisville, NH 03450, 1-603-827-3811.

Solar hardware and glazing are available from Solar Components, 88 Pine Street, Manchester, NH 03103, 1-603-668-8186.


 

How to Build the Solar Appliances

The Solar Pod
The Solar Pod is the primary appliance of the American intensive system. It is the most versatile of the solar appliances, useful for shading plants in the summer and for warming them in the fall, winter, and spring. If you have only one appliance, the Pod is the one to choose, because it is the most thermally effective, represents the most efficient use of materials, and is a manageable (four by eight foot) size.

Accessories for the Pod include the Pod Extender, the drop frame, the permanent insulated base, and the Pod lifter peg, all discussed later in this chapter.

Materials for the Pod

The Solar Pod requires the following materials (see diagrams below):

14' x 4' sheet of 3/4" AB exterior grade plywood (for A, B)

2 pieces of 8'-long 2" x 4" pressure-treated pine (C). Select the straightest, most knot-free lumber possible, since it will greatly simplify Pod assembly

2 8'-long 3/4" x 3/4" wood strips, to be used as the outside pressure strips (F)

1 8' piece of 2" x 2" wood, to be used as the end of the plate stiffener (E)

16 feet of 5'-wide .040-inch Sunlite fiberglass, used as glazing (I, J)

40 square feet of angelhair fiberglass insulation (H)

1 bent piece of conduit piping, used as a snow support (K)

1 4' x 4' piece of 1" rigid foam board insulation (D)

2 6" metal handles, optional (G)

1 tube clear silicone caulking compound

The fasteners include:
110 #8 3/4" aluminum pan-head (sheet metal) screws
28 #8 1½" plated flat-head wood screws
8 #8 2" flat-head screws
9 #14 3" plated flat-head screws
6 ¼" USS plated flat washers 12 to 14 roofing nails
20 (approximately) 1½" finishing nails
4 3 / 4 " x ¼" round-head machine screws with tee nuts to match. These are used to fasten the handles to the Pod.

A small amount of wood glue 1 quart of polymer, to coat and maintain the fiberglass glazing
1 quart of Cuprinol #10 wood preservative and/or oil-based exterior paint

Fabrication of Pod Parts

We recommend fabricating all of the Pod parts before assembly.

Make a paper or cardboard pattern of the plywood end (A) and the plywood glazing supports (B). The glazing supports need not be made out of one continuous piece but can be made with several pieces from plywood scraps. Trace the end plates onto the plywood sheet and cut out with a saber saw. On the plywood scraps, trace the end glazing supports and cut these out.

Glue the glazing supports to the end plates and fasten them with small finishing nails. When the end plates are assembled, clamp them together, back to back, so that their glazing surfaces can be sanded smooth and made exactly the same on both ends of the Pod.

Next, predrill and countersink the holes in the outside bottom corners of the end plates where the 2 x 4s fasten to them. The holes for the two-by-two inch end plate stiffeners (E) are drilled into the end plates (A) and countersunk approximately eight inches apart.

At this point you can attach the end stiffeners to the inside of the end plates. Hold the end plate stiffeners flush with the bottom of the end plates using wood clamps. Drill from the outside of the end plates where they are countersunk just into the end plate stiffeners. Secure the pieces with the two-inch flat-head no. 8 screws.

Paint all wood pieces with Cuprinol #10 and with the oil-based paint, if desired, after the Cuprinol has dried. (Do not use latex paint, since it will not stick to the Cuprinol.) Do any treating or painting in a well-ventilated area.

Make a template for the foam board insert (D), allowing two inches from the bottom end to make room for the end plate stiffeners that will be attached later. Cut the foam exactly to size so that it will fit snugly. Do not place the foam into the end plates until after the glazing is done.

Cut the two side rails (C) to size—94½ inches long. Drill a 3/4-inch-diameter hole about one inch deep in the center of each upper edge to accommodate the snow support (K). Then plane the upper outside edges so that the glazing will fit flush over the outside of the rails. Cut the pressure strips (F) into 96-inch lengths, putting a slight taper in each end. Mark the outside of the pressure strips with a countersink drill at 10-inch intervals. Treat these pieces with Cuprinol #10 and leave them to dry. They can be painted later, when the Pod is assembled.

Solar Cones

Once we settled on the ideal profile for the Solar Cone, we made prototypes of different sizes, ranging from small ones, about 12" in diameter, to one large enough for a person to sit in briefly—and one 10' in diameter, or greenhouse size. After many trials and long usage, we found that the most useful and material-efficient size is the 35"-diameter Cone. This size can easily cover a mature plant or be used to start a quantity of seedlings.

Strictly adhering to the accompanying cutout pattern is very important. The angle of the Cone's sides and the size of the top opening are both critical to its performance. While the size of the Cone can be varied, the ratio of the top opening to the volume must be maintained.

Staggering the Cone pattern on a 3'-wide sheet of Sunlite (.040- thick) wastes the least amount of material. For your first Cone, we recommend making a paper pattern. Draw the pattern directly on the fiberglass sheet with a marking pen. Cut it out, drill the holes as shown in the accompanying plan view, and file the edges smooth with sandpaper. This Cone then becomes the pattern for subsequent cones.

Draw the pattern outlines for the Cones on the fiberglass sheet, as shown, then cut them out either with a pair of sheet metal shears or with a saber saw fitted with a fine (18- to 24-tooth) metal blade. The saber saw is not as hard on the hands and will result in a smoother cut.

Smooth the edges of the Cones with medium-grade sandpaper or a medium file.
Then carefully predrill the holes for fastening the Cones so that, when the edges are overlapped, the holes will align. Cut, drill, and finish-sand all pieces before assembling.

To assemble each Cone, start with the bottom holes at the base. Slowly squeeze the sides together, aligning and fastening each hole on the way up. Fasten the last hole with caution so as not to crack or craze the edges of the top opening. To fasten the Cone, we recommend either 3/8 "-long nylon machine screws with hexagonal nuts or aluminum pop rivets with washers. Machine screws are removable, letting you take the Cones apart and store them flat.

Aluminum pop rivets expand at roughly the same rate as fiberglass. Even though they don’t allow you to disassemble the Cones, we have found that we never take ours apart because they store perfectly well stacked on top of each other.

When using a Solar Cone, push the bottom edge into the soil in order to seal it. Any air that leaks into the bottom will create a chimney effect inside the Cone, venting out moisture and heat, letting in cold air, and negating the solar-heating advantages of the appliance.

To make the Cone function as an insect barrier, cover the top opening with fine mesh screening held in place with fine mesh screening held in place in place with boddypins. On cold nights, stuff mulch hay or other soft material into the opening to prevent heat loss and protect plants from light frost.

To combat weathering, coat your Cones with liquid polymer on both sides every two or three years. Store the Cones under cover whenever they are not in use in the garden to prolong their life.

Now cut the fiberglass. The inner or lower glazing (J) should be 94½ inches long and the outer or upper glazing (I) should be 96¼ inches long.

The angelhair insulation can be cut later, before you attach the upper glazing to the Pod.

Assembly of the Pod

The first step in assembling the Pod is to attach the end plates (A) to the two-by-four-inch side rails (C). The end plates and the side rails form the chassis of the Solar Pod. Place the 2 x 4s parallel to each other on the floor, four feet apart. The beveled edge of each should be facing out, and the snow support hole should be facing up. Place the end plates so that the bottom edge of the glazing supports (B) cradles the end of the side rails (C). The sides and the bottom of all these pieces should be flush (see figure 8-8).

Square up all the corners with a carpenter's square. Drill small pilot holes through the predrilled holes in the end plates and into the side rails—eight holes in all, two at each corner. Fasten with the three-inch flat-head screws. Check again to make sure the corners of the rectangle are square.

Turn the Pod chassis over. To prevent it from rocking, brace it underneath with wooden chocks. Adjust the tops of the end plates so that they are 96 inches apart, measured from the outside of one to the outside of the other. Check this measurement again before fastening the glazing. The inside dimension, where the inner glazing is seated, should measure 94½ inches.

Rest the inner glazing (J) on the glazing supports (B).

Once the glazing is in place, drill a centering hole through it near the middle of the glazing supports and slightly into the wood. The diameter of the drill bit should be the same size as a #8 screw. The location of these centering holes will be covered with caulking, so mark their positions on the end plates (A). Remove the inner glazing.

Apply a bead of caulking approximately 3/16-inch round on all the end support pieces (B), but NOT along the side rails (C), because this would smear the glazing as it is being put into place.

Two people are needed for the next step. Replace the inner glazing, lining up the two centering holes. Touch the end plates with the glazing at the two holes and then rest the glazing outward. The glazing should fit perfectly in place, and any smudging of the caulking while placing the glazing should be minimized. Do not press the glazing into the caulking. Screw the 3/4-inch #8 screws into the predrilled centering holes. Secure firmly, but don't tighten all the way. Over-tightening will spread the caulking too thin.

Continue to drill and screw the rest of the inner glazing to the glazing supports. Start at the middle and work outward to the corners, placing the screws every 3 inches, until about 12 inches from the side rails (C).

Drill only one hole at a time and attach the screw before drilling the next hole. Gaps in the glazing are caused when all the holes are drilled at once.

To ensure that the screws go in straight, drill through the glazing and the caulking and just barely into the wood. Hold the screws straight while fastening them.

Next, apply a bead of caulking along the entire inside edge of the 2x4 side rails (C). It should be 1½ inches up from the line where the edge of the glazing will rest. All the long edges of the inner glazing should be parallel to the side rails. Otherwise, creasing of the glazing may result. If necessary, press up on one edge of the glazing to straighten it. When the glazing is correctly placed, drill a hole through the glazing and the caulking and slightly into the side rail near the middle of the rail. Avoid drilling where the snow support hole is. Fasten a ¾ inch aluminum pan-head screw at this central point. Working from the center outward, drill and place screws every six inches or so until you are within about 18 inches of the corner. Make sure that all the screws are bedded in caulking. Repeat this procedure on the other side rail.

When you have finished securing the long edges of the glazing to within 18 inches of the corners, alternately fasten a screw into the long edge (C) and then the short edge (B) until the corners are firmly secured. This will help prevent creasing of the glazing. Fasten all corners in this way.

Next, fasten the metal handles (G) on the outside of the end plates. The rigid foam board insulation (D) should be installed now as well. It should fit snugly underneath the end glazing supports and up against the end plates. A few dabs of silicone caulk will help to glue it in place.

Turn the Pod upright. The next additions are the snow support rib (K) and the angelhair insulation (H). We recommend adding this snow support rib regardless of whether the Pod will be used in a northern climate. The rib will help to extend the life of the Pod should the wind blow it upside down (or if someone faints on top of it). Insert the snow support rib into the predrilled holes. If the rib is sitting or pressing against the top of the inner glazing, remove it and insert flat washers into the holes as shims to raise the rib to a level where it will be centered between the inner and outer glazing. Put a small amount of caulking in the hole, replace the rib, then caulk around the base of the rib where it enters the side rails.

The angelhair insulation is fitted to and placed on top of the inner glazing. Hold it in place by tacking the edge with a staple gun into the wood, close to the inner glazing. Where the edges meet, feather them together for a smoother appearance. Cover the snow support rib over and under with the angelhair insulation.

Now the Pod is ready for the top glazing (I). The upper glazing will extend beyond the outside of the end plates by 1/8-inch on either end. Lay the outer glazing on the frame. Square it so that the bottom ends overlap the side rails (C) by the same amount on either side.

When the outer glazing is located perfectly on the frame, drill two centering holes at the top of the end plates (A). Remove the outer glazing. Apply a bead of caulking to the middle of the upper edges of the end plates. Extend the bead of caulk along the entire upper edge of the end plates down to the side rails. Any holes, blemishes, or low spots in the wood along the bead should have extra caulking forced into them as filler.

Wipe any dust off the underside of the glazing. Two people are needed to reposition it and align the center holes with ¾-inch pan-head aluminum screws. Starting from these screws, work toward the corner of the glazing, drilling and inserting screws about four inches apart. Fasten the glazing up to about 16 inches from the corner.

Adjust the long sides of the glazing so that there are no creases in it. This is done by pushing up on the middle of the long edge. If there is a crease that just won't disappear, remove and readjust some of the screws closest to the corner until the glazing forms a smooth curve along its whole length. Once the glazing forms a smooth arch, draw a line along the bottom edge of the glazing on the side rails (C). Lift the edge of the glazing slightly and apply a bead of caulk ½ to ¾ inch above the entire length of the line. Tilting the frame while applying this caulking will make this step easier.

Stretch measuring tape along the long side of the glazing below the line on the side rails. Mark with an arrow at 7 inches, 24 inches, 41 inches, 70 inches, and 88 inches. Make sure there are no creases in the glazing and then fasten with a roofing nail above the center arrow through the glazing, through the caulking, and into the rails. Nail from the center outward. Continually check to make sure that there are no creases. Repeat this procedure on the other side of the Pod.

The pressure strips (F) will be attached over the glazing, the caulking, and the roofing nails. These strips serve several purposes. They hold the edge of the glazing from ripping and they also provide handles for lifting the Pod open on the side.

Place the pressure strip flush with the top edge of the side rail (C). Using a drill bit that is the same size as a #8 screw, drill at the countersunk places through the pressure strip, the glazing, the caulking, and just barely into the wood rails. Fasten with a #8 plated 1½-inch flat-head screw. Continue this process, working from the center outward until you are within about 18 inches of the corner. Keep an eye on the arrows to avoid drilling into the roofing nails. Repeat this on the other side of the Pod. Finish securing the corners of the glazing into the end plates (A), alternating from side to bottom and ending at the corner.

If there are any rough spots on the overhanging edges of the upper glazing (I), sand them gently with a medium-grade sandpaper. Be careful not to sand them completely flush with the end plates. Place a small bead of caulk underneath the slight overhand along the upper edges of the end plates (A). Running a finger along the caulk will smooth it and form a subtle overhang, preventing moisture from creeping back into the upper wood surfaces of the end plates.

As a final step, the pressure strips can now be painted on the assembled Pod.

Copyright © 1994 by Leandre Poisson and Gretchen Vogel Poisson. Reprinted from Solar Gardening: Growing Vegetables Year-Round the American Intensive Way, with permission from Chelsea Green Publishing Company.


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Post a comment below.

 

Fran Melheim
8/11/2009 7:02:24 PM
Don't know if this will help you, but found this at my local library website: Poisson, Leandre, 1935- Title: Solar gardening : growing vegetables year-round the American intensive way / Leandre Posson and Gretchen Vogel Poisson. Publication Info.: White River Junction, Vt. : Chelsea Green Pub. Co., 1994.

Fran Melheim
8/11/2009 7:02:00 PM
Don't know if this will help you, but found this at my local library website: Poisson, Leandre, 1935- Title: Solar gardening : growing vegetables year-round the American intensive way / Leandre Posson and Gretchen Vogel Poisson. Publication Info.: White River Junction, Vt. : Chelsea Green Pub. Co., 1994.

Cathy Cline
10/21/2008 10:05:23 PM
I've spent all day looking for some kind of solar heating/frost protection I can place over a particular plant for the winter. I read about Leandre Poisson's Solar Cone on this website, but can't seem to find any place where I might purchase one of these. He describes how to build one, and offers a kit to build one yourself - but these are beyond my capabilities. Does anybody know where a pre-made cone might be purchased? Thanks for the help.








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