Has anyone tried Greenhouse within Greenhouse for Giant temp swings (115 day, 30 night) ?

I have a 20 x 12 greenhouse which gets way too hot in the day and  way too cold at night.

I’m not asking for additional suggestions on what to do in the situation because there are hundreds of posts on that. I will be addressing the heat issues this summer. And come with a strategy later.

FOR NOW I simply want something to put seedlings in.

Has anyone tried a greenhouse within a greenhouse?  I was about to setup a small portable greenhouse I had to test this out with temperature probes, but it looks like it got shredded this winter.

I was hoping it would not get as cold or hot within this second greenhouse.

I would think the greenhouse in a greenhouse would get warmer during the day, and stay warmer at night, than the surrounding greenhouse.

I recall Elliot Coleman (Four Season Harvest) used row cover inside his green house as an extra cold weather layer, and I *think* I remember him using two layers with an airspace in between. This isn't *exactly* what you're asking, but it indicates that this could work.

However, if it were me, I try to insulate the north wall of the inside greenhouse, and consider putting some jugs of water as a bit of thermal mass as well.

How small is small?  Could you put the water jugs on something with wheels and put it in a sunbeam during the day, and wheel it in with the seedlings at night?

Hi, thanks, this is helpful. My greenhouse gets full direct sun, and my backup method was to fill milk jugs with water and surround the seedings. I’ve saved up about 15 of them. It gets so hot in the greenhouse I would just leave them in there as opposed to trying to find a sunny spot (the poly takes a tiny bit of suns energy but turns the greenhouse into the sauna it becomes).

I will be buying shade cloth for summer. And leave the doors open once things get too crazy.

I bought some more temperature sensors, one I intended to put on the floor of the greenhouse in a greenhouse to see if that works. I no longer have that bought I had bought a sensor to put on the floor of the main greenhouse to compare it to. Today I learned the floor of the greenhouse was 80 compared to 100 about three feet up - so there is hope they won’t get fried - but that was at 3pm.

I too think the greenhouse in a greenhouse idea could be even hotter in the second enclosure, but I was hoping the dense material of the inner one would have brought down enough transmission (in addition to the poly) to counter that - so in a way it could shade it a bit.  The main idea is to bring up night temps which I don’t have anything I can do to mitigate.

To give you an idea of how crazy Colorado is, here’s a week at the end of March

Check out this One Yard Revolution video:

Just watched it, thanks. I do remember discussing these ideas before here— of low tunnels inside a greenhouse and then agribon on top for even more.

As anything good, this is something I would need to constantly adjust as my conditions change.. which in my case would be daily because it nearly always gets to 100 degrees F in there before 11am.

A Ground to Air Heat Transfer system could cool your greenhouse during the day and provide heat during the day.
They can be prettysimple, here's a video from Sean of Edible Acres that shows a very basic system:

Not quite your question.  I have done wall of water's inside a greenhouse and that is enough to keep seedlings alive if that helps.

Some greenhouses have double layers of materials with airpumps to inflate and keep them separated.  The air between the two layers serves as insulation so it's not getting too hot when the sun is out but retains heat at night. If you have double glass door and single layer glass door at home, you will observe similar phenomenon. So a second greenhouse inside would work temperature wise. I am not sure about light intensity though, the seedlings might need more care to acclimate if they will be transplanted outdoors later on.

I am trying something similar to the what the OP wants this spring.  But it is my first year and I just got it set up two days ago so I don't know for sure if it will work.

I have a insulated greenhouse.  The south wall is double pane glass. The north wall and roof are insulated with foam and the two end walls are part insulated and part glass.  

Inside the greenhouse, along the north wall I put 4 commercial refrigerators with glass fronts.  I have the shelves full of planted pots I want to start and a light bulb at the bottom of each fridge.

Because the roof is insulated and there are eaves that shade the greenhouse when the sun is high the fridges only see direct sunlight early in the morning and near sunset.  The rest of the time they are shaded and benefit from the protection of both heat and cold the greenhouse offers.    

Last night it got to almost freezing and today it was cold and raining all day.  With the light bulbs on the entire time, the coldest the fridges got was 65F at about 6am and the warmest they got was 78F yesterday when the sun was setting and they were in direct sunlight.

My plan is to put a thermostat that turns the light bulbs off  when it gets to 80F  and turns on a van to vent them if it gets to 90F but it hasn't arrived yet.

We treat plants like they’re some kind of foreign alien life form.  But wait, plants enjoy similar conditions as people.  What if we used our own intuition.  Imagine you were camped-out in the greenhouse all night, what would you do to stay warm?  Cover up with a blanket or whatever insulation was available?  Maybe take a hot water bottle to bed?  

Wow! I thought Louisiana was bad as far as Temps go... our humidity is what makes it bad, so I'm interested your greenhouse strategies.  I plan on a DIY greenhouse and it'll be my 1st 😊
So, I welcome any suggestions, comments or DIY selfies 🤳 😊

Missie

Melissa Landry wrote:Wow! I thought Louisiana was bad as far as Temps go... our humidity is what makes it bad, so I'm interested your greenhouse strategies.  I plan on a DIY greenhouse and it'll be my 1st 😊
So, I welcome any suggestions, comments or DIY selfies 🤳 😊

Missie

Hi, I think you're situation is much different because of the humidity.  In Colorado the reason it gets so cold at night is because it's so dry.  My intention is to level out the crazy swings.  You may just need to work on keeping it cooler - so less insulation.