While the afternoons have warmed up a bit, morning temperatures have been in the low forties two days in a row. Plants in the greenhouse are probably safe from light frosts, but cool weather could still push them into ending their seasons early.
I had some rearranging to do in order to make better use of the space and it was time to close gaps and get the greenhouse ready to be heated.
I had some rearranging to do in order to make better use of the space and it was time to close gaps and get the greenhouse ready to be heated.
I started by covering the north wall with 4 mil plastic to add an extra layer of dead air space between the inside and the cold winter wind. With that done, I moved my plant shelf from the east wall to the north to make better use of available light. Our original plan was to put shelves along three walls, but once we got started, it just wasn't practical or necessary.
Shade cloth over the roof helps reduce daytime heating, which can be a problem even on cool days. Grommets in the fabric allow the cover to be rolled up where extra light is needed.
Vents on the roof can be opened even under the shade cloth to release hot air and aid circulation. They need to be closed up for the winter. Opening the door and using fans should provide enough ventilation in cool weather.
The main heat source in cold weather will be this 1500 watt oil-filled heater. The fan behind it will stir the air preventing cold areas away from the heater.
This oscillating fan will help circulate the air giving plants a fresh breeze.
Gallon jugs along the south wall, painted black and filled with water provide thermal mass, collecting and holding heat during the day and releasing it to warm the greenhouse at night.
This thirty gallon black trash can is filled with water to provide additional thermal mass. The lid was lost years ago in a windstorm, so I covered the can with a black plastic trash bag to keep mosquitoes out. In looking at other people's setups on YouTube I saw one greenhouse with water-filled coffee creamer bottles tucked into extra available space in order to harvest the sun's energy for additional heat. The dark blue tubs full of soil I use for growing tomatoes and peppers should also collect heat during the day. Keeping the temperature above freezing is essential. Keeping it in the fifties would be ideal.
Tomatoes and peppers in buckets and tubs on the floor line the south wall of the greenhouse.
The high ceiling is good for headroom and air circulation, but it could also steal some of the heat. We'll see how it goes this year. I may put in a lower 4 mil plastic ceiling for next winter.
On mild days I open the doors to let out excess heat, but at night I close them up tight.
Stephen
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