We have three homemade cold frames in our backyard now, where we are growing our greens. We’ve already had about three feet of snow so far this season, but our greens are doing great. Here’s a picture of one of the coldframes, and a close-up shot of the greens inside it.
The glass is just old double-pane doors that we found at the Habitat for Humanity store. The frames are made from 2x4s (we bought the long ones, and salvaged the short ones from a lumber yard that was giving them away). They have some foam insulation in the end walls, and weather stripping around the doors, but the insulation is pretty minimal overall, and they aren’t heated at all. On sunny days, it’s often over 100 degrees inside the cold frames, even when it’s in the 30s outside. During the night, the temperature inside drops to about the same as the outside temperature, so these sort of frames will really only work for things like greens that are pretty cold hardy.
I make green smoothies for us everyday, and before we were growing our own greens I would spend at least $15/week on organic greens. During the summer, the greens in our local store come from farms in the area, but when I look at them now, I see labels from farms on the other side of the country (places where they haven’t had three feet of snow so far this year). So if I were buying our greens, not only would I be spending at least $15/week, but I would also be contributing to the pollution that goes along with trucking food halfway across the country.
Our cold frames were very inexpensive because most of the materials were used. My husband came up with a pretty simple design, and it works perfectly if you get a decent amount of sunshine during the day – regardless of how cold it is outside. As long as there is sun hitting the glass, the greenhouse effect will heat things up.
If you have a decent amount of sunny days in the winter, see if you can grow some cold-hardy plants. It’s such a welcome sight to see bright green leaves growing in the middle of a brown (and white) landscape this time of year.