My greenhouse isn’t sealed really well

[Guest]

So I hooked up my thermostat outlet the other day and it seems to be working. The light is on when it’s cold.

Been checking my temps though, and not real good.

Last night it hit 21 outside, and I recorded 24 in the greenhouse.

Night before it was 29 outside and I recorded 30.9 inside.

No, my greenhouse isn’t sealed really well. About 8 x 15 hoop house with double plastic on it, a single 55 gallon barrel of water, and shade tarp over one side.

So here are my thoughts or my questions:
1. I plan to get a small fan to move the air around. Think that will help.
2. Think I need a second heat lamp.
3. Where so I place the thermostat plug?

Up high might get cold first, but also afraid it will warm up faster when the heat lamp comes on.

Or down low, perhaps not right on the ground, but in a corner a few inches off the ground?

What are your thoughts?

Thanks.

[Holly]

You'd be better served by using smaller hoop tunnels inside the hoop house with heavy weight frost blankets on them. You're not going to get that hoop house 20 degrees warmer than the outside temperature, or you'll go broke trying to do it. If you situated it in a micro zone that is very protected on the North side, you might replicate 1 zone warmer.

[Dan]

Not sure what you are using but the thermostat plugs I have seen turn on just above freezing. The circulation fan will help eliminate cold spots. One heat lamp is probably not enough.

[Robert]

You can't maintain higher temperature with that setup in those outdoor temperatures. Use it for seedlings in spring. You might be able to grow winter crops without adding heat. Otherwise, you need a serious heat supply.

[Liz]

I don't try to heat my hoophouse, that would be futile and expensive! If temps are low enough to put my cold hardy veggies at risk, I put frost blankets over my beds and heat lamps under the frost blankets.

For more tender plants/seedlings, I place the plants on top of my barrels of water and use frost blankets and heat lamps. The barrels absorb heat from the sun during the day, so they give extra protection to more tender plants.

I put the heat lamps inside of old metal poultry feeders so the hot bulbs can't touch vegetation and start a fire.

[Owensboro]

This website will help calculate howany BTUs you will need to keep a consistent temperature in your greenhouse.

You should place your thermostat where your plants are placed. This will give you an accurate temperature where your plants are growing.

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https://www.acfgreenhouses.com/greenhouse-heater-size-calculator.aspx