Greenhouse getting ready for the cold

It was sunny here Dec 8 so I took a few pictures. It’s currently 18 F outside feels like 10 / greenhouse is in the 40’s. Tonight is a test to see if I get any frost. But shouldn’t be getting any colder tonight. Thanks for looking!


Are you heating the greenhouse in any way? How thick is the plastic used in the walls?

Can you tell us a little about the size/construction and how you heat/cool it? Do I see Christmas lights in the 3rd picture? And do you grow any food over the winter?

yes I use a 1500 watt? is it,heater. Nov I had it on during some nights (it would turn it’s self off during the day) as of dec it stays on with a fan circulating the air which has helped from frost in the past. I honestly can’t remember how thick. is it 6 mil? the thickest? I tried to get the thickest and double layered it. Some air gaps through out, I could have done better. but for this year it should be ok. I just realized the heater is on medium not having to go full force.

I only use greenhouse in spring for my starters. I found it is very expensive to heat it with electric when nights are around or bellow freezing point. To help with the cost of heating I bought a couple rolls of reflective Insulation (flexible foam with reflective cover on both sides) and made kind of removable greenhouse cover that I set up every night and removed every morning. The difference was huge even in spring and should be much more in winter when days are shorter. But my GH is relatively small - 6’X8’, 7’h, not sure if it will work for you.
You plants look so nice and tropical - do they tolerate 40F OK?

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I used to have a 8’wx10’l last year that I downsized to a 8’x8’ 7 ft high. It’s like a big square knowing my measuring skills LOL. All Pvc hoops into rebar plastic and door was done last. some wood was put on the sides and the top roof. second layer of plastic was added end of Oct. During winter I heat with a electric heater and fan. I do grow carrots, kale, spinach, collards, and celery over the winter with some citrus Those Christmas lights are around the dwarf cavendish stem for decoration. The light give off very little heat if any. Thanks for the comment

I may need to get a 2nd heater running when it goes below 0 F next week

I have seen that reflective insulation stuff, I will end up picking some up next month. Just extending the growing season can be enough. Last year it was so cold with a 10’ft gh I closed it down from Jan to end of March.
Thank you they do fine in the 40’s. I really doubt I should get any frost. if anything some cold damage

Thanks Matt. Wondering if there is an air layer between the 2 layers of plastic.
My hoophouse is unheated. It has gotten down to the mid 20’s in there so far but can get lower - like down to 8. When that happens I add row cover over low hoops to capture ground heat. I’m growing lettuce, pak choi, cabbage, carrots, cilantro, spinach, chard, leeks, celery, scallions, snow peas, celtuce, and an experimental potato, LOL. Have done all of these except snow peas and the potato, w/o problems in my zone. Haha but we are all aspiring zone pushers.
I have a couple solar panels that charge a 12V battery set that runs a fan in there. I’m thinking about putting some car Christmas lights in there (that run off 12V). Still researching it.

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Sound like you have a great system going! thanks for sharing, I have some pak choi seeds I should start now knowing they’re cold weather crop. I have some air pockets but not everywhere. There is a woman on youtube from way north in Canada that has built a greenhouse with 1 1/2 - 2 inch air pockets in her walls. Framed like walls in a house would be. plastic on both sides. The temps there go down to -30 F so I can’t imagine that even being enough. Luckily most of us will never know what that feels like (: