Cold Frame, Hot Materials

Hot not as in 'stolen', rather used here to mean 'found', and free, and useful for framing, mass and insulation. Now that's totally cool. A cold frame is a structure that surrounds a garden bed, allows light to penetrate, has an insulating mass on the interior, and thus allows gardeners to extend their growing season.

I set out this past weekend to locate discarded items useful for making a cold frame to cover one of my vegetable garden beds. I have never before made a cold frame and while I have a complete landscape plan for the lot (see upcoming post), I wanted to get something built NOW.

Today, I made a very simple cold frame that can be constructed in a very short period of time (depending on how well-developed your project is when you begin).

I began with a garden bed that has already been in use, and even had small plants that I grew from seeds several weeks ago.  My ‘found’ materials include:

• 2 windows (approx. 3’ x 4’)
• 2 wooden boards (2” x 10” x 8')
• several bricks

Cold Frame Framing

In this picture you can see where I put the boards, which will contain the soil, and the bricks, which will absorb heat from the sun and slowly release it through the day. Currently, the boards are being held up by other bricks but will soon be held together by nails with shorter wooden boards on the ends.

The board on the south side (right) is nestled into a trench about 2 inches wide and 2 or 3 inches deep, spanning the length of the board. This places the board lower than the other and allows the windows to angle just a bit southward, towards the sun. (For my ideal cold frame, the framing will be designed to place the windows at an angle appropriate to Chicago’s winter solar position).


Cold Frame Finished

It took me about two hours to build this cold frame. While it was designed to be a temporary structure, it’s one that I know has worked for others. When I’m enjoying fresh spinach in January, I’ll let you know.