Partly underground greenhouse progress

Location:
- Eastern Europe
- USDA hardiness zone 4 or 5
- 700 m (2300 ft) above sea level

Planned:
- 34 sq m (366 sq ft) inside
- northern side underground 150 cm (5 ft)
- base built of stone, with concrete on top
- steel frame
- twin-wall polycarbonate roof and walls

I do not expect it to stay warm in winter, but my precious plants should be safe for two months longer at least.

Progress so far:

The backhoe did most of the earthwork, it was done in an hour.

On the first day, we mostly experimented with the possible variations.

Then, the rain came.

Day 2: we dained the water, brought home more stone and built some more (just me and my father).

Day 3: My father-in-law was helping a lot and we saw real progress.

This is what we have accomplished this far.
Sadly the weather cooled down very much, to -7C (19F) in the mornings, I've lost all hope to pour concrete this year.

Looks beautiful man. What do you put for flooring?

Kinda jealous of your orange toy. I've been diggin a pond with a shovel. 30+ hours so far. I'm ripped now.

Welcome to permies Elemer ! Great looking place you have there. Keep us updated on your progress.

Charles Laferriere wrote:Looks beautiful man. What do you put for flooring?

Kinda jealous of your orange toy. I've been diggin a pond with a shovel. 30+ hours so far. I'm ripped now.

I plan to just put in some good soil and plant in it, no flooring whatsoever..

I would like to own that orange toy, too. I called in a professional for the job, he also dug a small pond on the same day. I'm also looking for some cheap liner for that, EDPM is very expensive. There is no constant water source except for a well, so a good insulation is needed. (I plan on using mostly rainwater to fill it)

Elemer, you may be able to seal your pond without a liner, check out this thread for info..

https://permies.com/t/38201/ponds/Progress-Gleying-Pond-Pigs

Miles Flansburg wrote:Elemer, you may be able to seal your pond without a liner, check out this thread for info..

https://permies.com/t/38201/ponds/Progress-Gleying-Pond-Pigs

Thank You, Miles. I did read that thread, but this is my first pond.. If I use pigs, then I have to wait until next summer, and lose all the winter rain and snow..
My soil is almost entirely clay, so maybe I could compact it even without animals.

The biggest problem? I have to go to work every weekday, and these projects need a lot of time.

So the weather got warmer and we did this

Nice work! We built a sort of earth-sheltered or pit coldframe. I found that, although it would heat up very nicely during a sunny day, the soil temperature was too low for the plants to really grow. It only held them, you might say. If it was sunny and 20 degrees (F) outside, it could still be 70 degrees (F) inside, but the cold soil was maybe 35 (F) and would rise a bit, but not enough for our lettuce, spinach, and radishes to grow. I have spent the last year building a system to add bottom heat, which I believe has got to help a lot. Welcome and good luck to you!

Tim Malacarne wrote:Nice work! We built a sort of earth-sheltered or pit coldframe. I found that, although it would heat up very nicely during a sunny day, the soil temperature was too low for the plants to really grow. It only held them, you might say. If it was sunny and 20 degrees (F) outside, it could still be 70 degrees (F) inside, but the cold soil was maybe 35 (F) and would rise a bit, but not enough for our lettuce, spinach, and radishes to grow. I have spent the last year building a system to add bottom heat, which I believe has got to help a lot. Welcome and good luck to you!

Thank you, Tim!

I didn't think the depth would influence soil temperature so much.. It remains to be seen. It is only about 20 cm (8 in) deep on the south side, and 1 m (3.3 ft) on the north side.

More progress:

I got to the welding part. I don't like it and I'm not very good at it (vertical welds are difficult), but it has to be done.



I did this part alone, very boring and slow work, with hardly any visible result. The weather forecast says I can finish all of this...

Part of the polycarbonate is up. The wind made our work a bit harder, but the large pieces are already on their place, held by screws. I don't know what to put pn the top, where they join.
The two sides will be easier with smaller pieces, I'll only have trouble with the openings (window, door).

So here is the (mostly) finished building:


Front...

Back...

Inside.

The temperatures were very low this last week. It went down to -20C (-4F) at night, and sometimes came back up to just -14C (7F) during the day. The lowest I've seen inside (in the morning, at ground level) was -11C (12F). That isn't too high, everything would freeze to death, but the joints are not insulated everywhere, and it was one of the coldest periods of the year. Oh, and the thermal mass (the stone part) was probably still cooling the air..

The hens don't like it in there (they were roaming free before, now they eat what I drop in) but they benefit from the much milder temperatures.
I wish I could already plant something in there, but there is no hope before the end of February.

Hi Elemer,

While I'm in total admiration of the greenhouse (which I'm sure will gain a lot of seasonal heat this summer and be more clement next winter), what I feel most is pure envy for the deep black soil in your first photo!!! Someone has been doing something very right on your land!

That black dirt and the rock wall are beautiful! Have you considered the trade-offs of insulating the North roof instead of using the polycarbonate panels? I'm not sure how much sunlight you receive through it versus the heat loss all night long.

Love the soil that got dug out of there. It looked so beautiful. Your greenhouse looks wonderful.

I would build beds about 2-3 feet high. The cold tends to sink to the bottom. It will allow cold to settle to the floor leaving the bed warmer. If you put in planks in the alley way slightly above floor level it might allow the cold to settle under the planks. Making the whole greenhouse feel warmer.

I would also use what I call bubble pack or polydress. It acts as an insulator and light disperses more evenly. Well worth the investment.It also means plastic is replaced less often and over time pays for itself. Here is a Canadian company that sells it.
http://growtech.ca/ These guys are in Manitoba and they grow strawberries in their greenhouse.

I believe with the polydress and beds you can raise the temperature to an acceptable level to grow cool weather crops and maybe others as well. Start warming climate seedlings way earlier anyway.

Comment on sealing the joints. I have read that the cheapest and easiest way to seal the joints is to cut another sheet of the polycarbonate material into 3 - 4" strips (7 - 10 cm) and screw that in on top of the seams. It makes a pretty tight joint and routes the water off the joint. You might see if this would work on your application.

We built an underground greenhouse many years ago and it was actually 4-5 feet deep, insulated north with peak, and polycarbonate south simply using silicone or tube glue to seal the joins (which were on 2x4's)Walls were 2x6 construction, poly on inside so it was washable, and then welded wire panels attached to that with 1000 milk jugs filled with water and tied by the handles on all 4 interior walls. The roof line was above ground, but everything was grown 4-5 feet underground on straight soil. To enter you walked through the 4 foot tall entryway that was about 3 feet deep and bermed - you had two doors so you could go in, close the exterior, then open the interior to get into the greenhouse.
SCreened east and west roof so when it got warm it could be vented.

We routinely get -40 to -60 and that greenhouse never got cooler than -11 with no heat. On a decently sunny -20F day we could reach 80-90F with no heating. BUT we could heat the 16x32 greenhouse with a space heater easily as we had insulated blankets which you pulled across two rods at "ground" level (where the roof started), in order to not have to lose your heat to the poly roof which was above ground level. It was completely experimental as we new nobody who had done it, and only a couple of books even mentioned earth bermed or underground greenhouses.

None of this probably makes sense (hard to describe), and we had to leave that home and the new owner bulldozed the entire greenhouse which was tear worthy . . . Our new place has ground water at 6 inches most of the year so anything greenhousy would have to be bermed which we have not got around to doing as we have no extra dirt. . . Add a rocket mass heater and some chickens would love to scratch around all winter and you could be very self sufficient with fresh greens and stored foods. We don't try to grow things out of season in this climate, so this was used as a season extender for cold weather loving things and to start our heat loving things like tomatoes, peppers etc.





middle of winter


early winter - you can see where we pull blankets across to help retain ground heat each night


early spring


this is looking inside from the west end - I am standing at ground level looking inside


Anyway, this was far from perfect and yours is absolutely gorgeous with the rocks, but maybe gives some ideas for future projects !

I like this greenhouse. I like the log cabin I see next to it too, and the black soil. Life in Romania looks good ... if that winter weren't so very cold ...
Here the problem is the groundwater. Last winter I even had water in my cellar

Thanks for sharing, Jay. Really nice pics and a great idea.Too bad you had to leave that beauty behind.

I am interested in trying your milk jug idea. What pigment did you use to make the water in them black? I have been planing on trying strong tea in various recycled plastic bottles,which will give a dark brown and isn't toxic if one leaks .Yours look actually black,however.

My plan is to intersperse dark water filled bottles among the plants sort of like a mulch and use 50 gallon drums of water on the north wall. I may try your idea of attaching the gallon milk jugs to the east and west walls arranged around windows and doors,however. How exactly did you attach them to the wall using their handles? They do seem to stack neatly.

Hello Elemér !

Judging from the dark rich soil under your greenhouse, the style of your outbuildings, and the cold weather, you must be in Hargita County. I'm guessing Csík ...

Question: why did you decide to build the greenhouse frame using metal? Did you consider using wood ?

Nice pictures here guys. Thanks for sharing your work.

Heidi Hoff wrote:Hi Elemer,

While I'm in total admiration of the greenhouse (which I'm sure will gain a lot of seasonal heat this summer and be more clement next winter), what I feel most is pure envy for the deep black soil in your first photo!!! Someone has been doing something very right on your land!

Hi there Heidi, thank You

It may seem like the soil is great, but in reality it is mostly clay. It forms very hard clumps when dry.

Mike Jay wrote:That black dirt and the rock wall are beautiful!

Thank You Jay!

Mike Jay wrote:Have you considered the trade-offs of insulating the North roof instead of using the polycarbonate panels?  I'm not sure how much sunlight you receive through it versus the heat loss all night long.

This was the best I could imagine for a roof (I'm not a professional, and this was my first). I wanted to have a high roof with lots of air space. I was thinking about covering that northern part with something during winter months, but I'm not sure. I might be better off keeping the hens in there. Last winter they didn't stop laying at all!

Pamela Smith wrote:Love the soil that got dug out of there. It looked so beautiful. Your greenhouse looks wonderful.

Thank You very much.

Pamela Smith wrote:I would build beds about 2-3 feet high. The cold tends to sink to the bottom. It will allow cold to settle to the floor leaving the bed warmer. If you put in planks in the alley way slightly above floor level it might allow the cold to settle under the planks. Making the whole greenhouse feel warmer.

My beds are just 20 cm (~8 in) high right now (i hope to rise it with organic matter). But I do have the space for the plank thing. It seems like a very good idea.

Pamela Smith wrote:I would also use what I call bubble pack or polydress. It acts as an insulator and light disperses more evenly. Well worth the investment.It also means plastic is replaced less often and over time pays for itself. Here is a Canadian company that sells it.
http://growtech.ca/ These guys are in Manitoba and they grow strawberries in their greenhouse.

I believe with the polydress and beds you can raise the temperature to an acceptable level to grow cool weather crops and maybe others as well. Start warming climate seedlings way earlier anyway.

I know I have a lot of work to do with insulating the structure. But this is the first season, and I am very curious about the heat retaining capacity of the rocks.. We will see in September.

Mike Schroer wrote:Comment on sealing the joints.  I have read that the cheapest and easiest way to seal the joints is to cut another sheet of the polycarbonate material into 3 - 4" strips (7 - 10 cm) and screw that in on top of the seams.  It  makes a pretty tight joint and routes the water off the joint.  You might see if this would work on your application.

I do have leftover strips of it, so I might just use them around the doors and edges.. Thank You for the great idea.

Jay Stegman wrote:
Anyway, this was far from perfect and yours is absolutely gorgeous with the rocks, but maybe gives some ideas for future projects !

Thank You Jay. I am still experimenting..

You did a great job with yours, I'm sorry it got destroyed. I hope you can build the next one soon.

Levente Andras wrote:Hello Elemér !

Judging from the dark rich soil under your greenhouse, the style of your outbuildings, and the cold weather, you must be in Hargita County. I'm guessing Csík ...

Question: why did you decide to build the greenhouse frame using metal?  Did you consider using wood ?

Hello András!

Your guess is right on spot.

Well, about the metal..

I don't know how much time an untreated wood frame would have lasted (the polycarbonate panels have a 10 year warranty, and hopefully a longer lifetime)

there is already enough poison without that treated wood

earth berming means additional moisture

a wooden frame would need additional support, like posts inside the greenhouse

I am no carpenter