An update to my Cold Frame for one of our raised beds. I added a 150w and a 200w incandescent bulb to attempt to keep the cold frame from going below freezing overnight or on cloudy days. I hooked these up to a temperature sensor, so they will turn on below 45° automatically.
We are hoping to be able to grow and harvest some cold tolerant greens throughout the winter, this is an experiment to see how well our cold frame could manage with a little supplemental heating when needed.
I added an internet connected temperature and humidity sensor, so I could track the temperature swings. The Amazon bag is keeping my USB battery pack out of the dirt and a little more insulated.
You can see from January 30th on that the lighting I added is keeping the low temperature overnight from dipping as far. You can also see how high the temperature can spike on sunny days.
Once the temperature is 70-80°, the greenhouse opener arm will vent the frame, but I haven’t seen that happen yet this winter.
The real test will be in a week when we have a cold stretch of weather in the forecast. I think the lights will help, but won’t keep up with the cold temperature.
The plastic panels I installed provide some insulation, as they are dual wall with air trapped in between. But it would be much more efficient to only have the plastic panels where they are needed to let light in (south facing) and have better insulated panels for the other wall surfaces.