Monday, October 26, 2009

Greenhouse Winterization, part 2

The transition to the winter greenhouse garden continues....

We removed most of the cold intolerant plants, but kept a few Thai pepper plants that had some flowers and fruits on them, and they are still doing great. Frankly, I was happy to get rid of tomatoes for the year. My wife transplanted the broccoli and brussel sprouts into the ground bed that I started in flats, and she filled the rest of the ground bed with spinach, lettuce, carrots and radishes.

As far as projects to transition to the winter greenhouse, I installed two 55-gallon metal drums filled with water to act as a heat sink and thermal mass, but also to provide water for our watering needs. It was gratifying to fill these from our rain barrels, and this begins the winterizing of our rain barrels and their transition to downspouts for the winter.
Unlike the plastic olive barrels we use for rain water harvesting, the barrels we re using in the greenhouse are metal (for thermal conductance), black (for solar gain), and also act as good shelving and work surfaces. These are reused drums (clean) and are about $20 from Axmen

We’ll see how these work, only having 110 gallons of water will not provide nearly enough BTU’s to maintain the greenhouse above freezing alone, but coupled with other features, hopefully it is enough to provide benefits. Water, though a good heat sink, would need to be in a volume close to 500 gallons, based on the square feet of glazing and insulative value of my greenhouse, to have a significant effect if that was the only thing I was relying on to keep temperatures moderate. If nothing else, however, the metal drums do act as shelving and storage for water.

Other changes for the winter:
I disconnected the solar window opener on the east window, and covered the east and north window with 2” rigid insulation, the silver film will also reflect a bit more light to the greenhouse.
I installed a cold frame over 1/2 of the ground bed (see below). This is essentially a greenhouse inside the greenhouse. We'll see how it works, and I'll probably cover the other half of the ground bed- but right now it is an experiment- stay tuned for temperature data.
Left to do:
Install solar pool cover to south facing glazing
Install storm door
Activate the compost furnace

More posts coming soon...


  1. Wow, so much work....I hope you can keep it warm enough for at least a few winter veggies! Regardless, it is a beautiful greenhouse!

  2. That greenhouse always leaves me frothing at the mouth. I want one! Do I sound like a two year old? Anxious to know how it weathers!