Cold frame in a day

I built a cold frame! Here is the finished product:

I'm rather proud of myself, actually. (100% muscle power, I'll have you know.) I'll describe how I did it.

I (very) roughly followed these instructions from an article on GreenOptions.com. Actually, I only referred to the article for inspiration and a few tips. Here's what I remember taking away from it:

• Use plywood for the sides
• Use 2"×2" scrap wood pieces for connecting the sides together at the corners
• Attach wooden cleats to the tops of the windows (apparently a cleat is a projecting piece attached to something to prevent it from slipping)
• "Putting insulation on the sides of the cold frame doesn't do much for it, because so much of the heat captured during the day will be lost through the uninsulated window once the sun goes down."
• "... building a back wall for the cold frame from stacked bricks can serve as a heat sink to store more heat gathered from the sun, to help keep the temerature up through the cold night. Building a cold frame against a wall, or into a hillside, where there is more thermal mass to store the heat, can also be a strategy to push it even further."

Here are the ingredients you'll need to build your cold frame:

Note that the small pile of scrap wood depicted above is not an accurate representation of the scrap wood you will actually need. You will discover which pieces of wood you need as you are building (hopefully you like to solve puzzles). Many will need to be cut out of larger pieces of wood, which leads me to the other key ingredient that is not depicted: muscle power. I happened to have plenty to spare; hopefully you do, too. If not, perhaps you could find a neighbour that would be more than willing to show theirs off.

The first thing I did was attach cleats to the windows. You only really need one small piece of wood to attach to the top of each window, but I wanted to prop my windows up a little higher at the top, so I attached a 1"×3" as well. I used Robertson screws (square head), which are the best screws, and if you wish to find them in the States, best of luck. You can stick these screws on the end of a screwdriver and they usually won't fall off, allowing you to screw them in with only one hand. But I found that I eventually needed the force of both hands on the screwdriver to push it down at the same time as turning.

Now, something I forgot to take pictures of was my use of the compost pile for the north wall of the cold frame. I dug a chunk out of my compost pile leaving an approximately vertical, south-facing wall. Then I found a large piece of old countertop (this place has everything; don't worry, plywood would be fine) and propped it up against the compost pile. I then steadied the countertop in front using two cinder blocks that had been sitting by the side of the house - anything big and heavy, like stones from the brook, would work just as well. Then I shoveled compost back against the countertop to (hopefully) turn it into an effective heat sink.

The next piece I made was the front piece, which I arbitrarily decided should be 13" high. I wonder now if I should have made it shorter, because it has resulted in not quite as steep a slope for the windows as shown in the article. I guess your desired slope will depend on different things - the time of year you intend to be using the cold frame, your latitude, maybe more. Anyway, I wasn't much interested in worrying about these details. My plants needed a home!

To make this front piece, I found a plank of wood and cut it to the width of the two windows placed vertically side-by-side (I chose to make a squarish cold frame; if you're making a long rectangular cold frame, cut the plank to the length of the two windows placed horizontally side-by-side). Then I cut two 2"×2" pieces to 13" high, and screwed the ends of the plank to the bottoms of the 2"×2"s.

Then I lay the windows onto the north wall mentioned above, the cleats keeping them in place. I propped them up at the bottom using the front piece. I cut two 2"×2"s to attach to the back wall at the corners (to attach the side pieces). I also cut two 2"×2"s to line the base of the sides, as extra supports. Then I found a big piece of plywood behind the shed, propped it up against one of the sides, and traced where I'd have to cut it. This took some time to saw. Then I screwed the cut plywood piece to the 2"×2" attached to the back wall, the 2"×2" attached to the front piece, and the 2"×2" I cut for the base, as shown in the diagram. I did the same for the other side (using the remainder of the piece of plywood, in my case). Some of those screws were really hard to get into the 2"×2"s. Sometimes I had to take a break half-way through a screw and do something else before finishing it.

Finally, I boarded up the front piece with lengths of scrap wood. And the structure was complete!

I came up with the idea for the mirrors on the sides as I was falling asleep one night. We have this usused bathroom cabinet sitting on our back porch, and I figured I could make use of the mirror doors. I have no idea how much they'll help to gather warmth and light, but it seems logical.

To absorb more of the heat during the day, I placed a flagstone in the middle and surrounded it with bricks and shards of rock.

And we're done.