In the bright sun and near 60F weather this past weekend, my little hoop-house was heating up. It’s 80F in the picture taken mid-afternoon on Sunday. The vents open automatically at 80, so the temperature doesn’t go above that.
I hope I can figure out how to use my hoop-house this year before the end of April, which is when I put seedlings in it last year. Unfortunately, I’m not sure how to get it to retain heat at night. The big open hoop-house is not like my low tunnel, which retains heat fine. My double-layer low tunnel sits directly on the garden soil in a garden bed and the plants in it have survived all winter. I have a couple ideas for the hoop-house:
1- get a propane heater
2- put the plants directly on the cement on the floor with row-cover over them
I’ll try out the row-cover and see how that goes. I’ll put a flat of soil down there with a remote thermometer on it and row-cover on top. I’m curious if that will work.
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Our greenhouse doesn’t retain heat particularly well either! We use an electric, contained oil heater (looks like a small radiator on wheels) to keep it just above freezing, though it only warms the space up by about 10 degrees, so we have to wait until overnight lows are securely in the mid-upper 20s. It does the job well and we put it on a timer so it isn’t running all day. Good luck with your set up!
Interesting to hear your solution. I went ahead and purchased a seedling heat mat, 20 in x 50 in. I’m planning to run that on a timer, just at night. It advertises it will raise the soil temp 20 degrees F above ambient. I’m also planning to cover the seedlings with row cover (Agribon 19). This seemed easier and less expensive than a heater. Our nighttime low temperatures are gradually increasing. I’d like to put several trays out in the green house this weekend. Onions, parsley and wildflowers.
I’ve run out of room on my indoor plant shelf because I’m planting so many flowers this year. So a bunch or them will have to go to the green house to make room for brassicas that go in this weekend, and then peppers and eggplants the next!
I have seen some green houses with black water filled barrels on the floor. Then the lowest plant shelf sits on those. The idea is that the water warms up in the day and slowly releases the heat at night. I have no clue what kind of cold this setup would handle. One thing I like is that no power is needed. OTOH, if the hoop house isn’t up all year, the barrels need to be stored somewhere.
Yes, we considered adding barrels. Instead we put in the concrete floor. I think that probably retains some heat. My hoop house is up all year so I could try adding a water barrel or two some day.