greenhouse nonelectric greenhouse feasibility

I have a 4x4 raised bed with a metal frame around it that I'm using to grow watermelons vertically.  I'm thinking I may turn it into a cheap little greenhouse once I get done harvesting the melons, but I've never grown anything in a greenhouse before.  Can you raise peppers in a greenhouse without an outside heating source?  I'm in zone 8a/7b (central Alabama) and contrary to popular belief it can get really cold here in the winter.
 
I'm thinking the answer is no....
 
Plus one on dragonsfire's and solid7's posts.

No heat source at all might be tough, but you wouldn't likely need extra heat frequently. Something you could turn on temporarily when the temperature drops could get you through the cold spells.

Harbor Freight sells propane tank top heaters that get pretty decent reviews and aren't too expensive. https://www.harborfreight.com/15000-btu-tank-top-propane-heater-63073.html

That seems a little large for a 4' x 4' space, though. Maybe a backpacking canister stove on simmer would work.

A (very) small wood stove, something like a backpacking wood stove, might work, though you'd have to babysit it through the night.

Placing jugs of water around the interior of the space can buffer the inside temperature against outside temperature drops. And just an old-fashioned incandescent light bulb can take the chill off. Especially if you can cover the structure with a blanket or something.

I have an 18' x 30' frame I plan to set up and cover with plastic before fall and I plan to use the HF propane heater and a wood stove. I live in zone 6b/7a, I think. It has changed over the years I've lived here. I remember one winter it didn't get out of single digits for a solid week. But that was decades ago and I'm counting on climate change to do me a solid.
 
Sawyer said:
Plus one on dragonsfire's and solid7's posts.

No heat source at all might be tough, but you wouldn't likely need extra heat frequently. Something you could turn on temporarily when the temperature drops could get you through the cold spells.

Harbor Freight sells propane tank top heaters that get pretty decent reviews and aren't too expensive. https://www.harborfreight.com/15000-btu-tank-top-propane-heater-63073.html

That seems a little large for a 4' x 4' space, though. Maybe a backpacking canister stove on simmer would work.

A (very) small wood stove, something like a backpacking wood stove, might work, though you'd have to babysit it through the night.

Placing jugs of water around the interior of the space can buffer the inside temperature against outside temperature drops. And just an old-fashioned incandescent light bulb can take the chill off. Especially if you can cover the structure with a blanket or something.

I have an 18' x 30' frame I plan to set up and cover with plastic before fall and I plan to use the HF propane heater and a wood stove. I live in zone 6b/7a, I think. It has changed over the years I've lived here. I remember one winter it didn't get out of single digits for a solid week. But that was decades ago and I'm counting on climate change to do me a solid.
I've probably had it drilled into my head too much over the years from frequent camping, but I don't like the idea of leaving a flame unattended outside.  Some containers of water would be more what I would have in mind.  Has anyone actually tried that?  Sometimes we'll go on 3-4 day stretches where lows will be in the teens/twenties and highs in the thirties/forties.
 
Maybe I'll just plant some frost tolerant leafy greens instead.
 
Well, that's just a starting point.  Your research should draw you deeper and deeper into things like permaculture.
 
One idea...  Create yourself a geothermal mass stove, otherwise known as a "rocket stove".  The idea being, that with a minimum of fuel, you can heat up an earthen mass, which will stay at a more stable temperature than ambient heating, and slowly radiate it's imparted heat.
 
There are other options.  Such as burying a 55 gallon drum filled with water, and putting a submersible heater in it, and build your greenhouse around it.  Not completely free, but very low tech, safe, effective.  You don't live far enough north to have a really deep frost line.  So I might look at that method.
 
I could go on an on...  But you need to expose yourself to these ideas, and get a feel for what might work for you...
 
Not the same but similar:  We have a couple of cold frames in the back yard and I use 2 quart bottles of water painted black.  The sun warms them during the day and they warm the cold frame at night.  
 
SmokenFire said:
Not the same but similar:  We have a couple of cold frames in the back yard and I use 2 quart bottles of water painted black.  The sun warms them during the day and they warm the cold frame at night.  
 
is that enough to keep them alive through the winter or does that just extend your season a little bit?
 
Doelman said:
 
is that enough to keep them alive through the winter or does that just extend your season a little bit?
 
I'm in Chicago so it helps jump start and extend my season.  For you in Alabama I'd imagine it would help a lot for the infrequent cold snaps you have - but then again I don't know how cold it really gets by you.  
 
SmokenFire said:
 
I'm in Chicago so it helps jump start and extend my season.  For you in Alabama I'd imagine it would help a lot for the infrequent cold snaps you have - but then again I don't know how cold it really gets by you.  
 
Hm....well let's see, this January we had 6 days in the 20s, 6 in the teens, and 1 night in the single digits, it can get pretty cold here.  Probably too cold for containers of water to keep the plants warm enough.
 
Doelman said:
 
Hm....well let's see, this January we had 6 days in the 20s, 6 in the teens, and 1 night in the single digits, it can get pretty cold here.  Probably too cold for containers of water to keep the plants warm enough.
 
Yes it would appear so.  Good luck with whatever you end up using.  :)
 
Doelman said:
 
Hm....well let's see, this January we had 6 days in the 20s, 6 in the teens, and 1 night in the single digits, it can get pretty cold here.  Probably too cold for containers of water to keep the plants warm enough.
 
I still think you'd be surprised what a 55 gallon drum of water with an aquarium heater inside, is capable of.  You did say non-electric, but if you could make one small concession...
 
The rocket heaters is even better.  Those things are amazing.  I taught my kids how to make a survival version.  Most people teach their kids NOT to play with fire.  :D
 
Yes, it uses electricity, but requires only a few things to make it work.  
 
Under the right conditions, I believe something like this could carry you through the winter.  Here's what I used when I ran out of space in my indoor greenhouses early this spring, and the plants survived quite a few -40 degree F nights.  I'm in zone 7a/b, so I'm colder than your zone. 
 
minigreenhouse.jpg

 
 
First, an extension cord.  You will need to protect (insulate) your northern exposures and provide a heat source to protect the tender plants.  I used a cheap "mini-greenhouse,' insulated on the northwest by our home and on the northeast by an attached unheated garage.  The greenhouse was heated by a 100W incandescent bulb in a clamp light reflector (with the clamp removed), plugged into a wifi enabled smart plug, and controlled by a simple IFTTT routine that turned it on when the outside temperature dropped below 45 and off when it exceeded 60. It's hard to make out, but the reflector and bulb are what the arrow is pointing toward in the photo.  They're in a homemade hypertufa pot, which also acted as a battery to store and reflect heat.  There was also a wireless thermometer in the greenhouse, with the receiver inside our house, to monitor the temperature inside the greenhouse.
 
clamp light with reflector.jpeg

tplink minismart plug.jpg

 
There were a few nights when it got really cold, so I tossed an old moving blanket over the uninsulated sides.  And, some days the sun heated it up so much, I had to open the door for ventilation.  Excess humidity was an issue that had to be monitored daily, also, but a fan could address that.  All in all, it worked well.  You wouldn't really need the reflector, I already had it and it protected the light bulb from breaking or melting the vinyl cover.  The wireless thermometer was something I already had, and repurposed.  The most expensive part of the entire project was the ~$25 TP-Link wifi enabled plug, which I also already had.  It doesn't require a hub, just a wifi network and a smartphone app, and is also one of the few brands of smart plugs that are UL-labeled and listed.
 
Sawyer said:
Placing jugs of water around the interior of the space can buffer the inside temperature against outside temperature drops. 
 
Water is a great heater....I believe I've read it holds 4 times the heat soil will, and twice as much as concrete.
 
nmlarson said:
 
Water is a great heater....I believe I've read it holds 4 times the heat soil will, and twice as much as concrete.
 
Some light heavy reading on the subject... (graded from simplest to most complicated)  All of them come into play, if you want to consider using passive technology to build a greenhouse.
 
 
https://water.usgs.gov/edu/heat-capacity.html
https://insulation.org/io/articles/k-value-u-value-r-value-c-value/
http://www.aamanet.org/upload/file/Why_R_Is_Not_Simply_The_Inverse_of_U_September.pdf
 
And finally, a big ol' comparison.
 
https://www.engineeringtoolbox.com/specific-heat-capacity-d_391.html
 
Doelman said:
 
Hm....well let's see, this January we had 6 days in the 20s, 6 in the teens, and 1 night in the single digits, it can get pretty cold here.  Probably too cold for containers of water to keep the plants warm enough.
 
January was brutal down here. I use up to 4 x 40w incandescent and a blanket wrap to keep it above 40° F in my hillbilly winter shelter. It's attached to the south side of our pump house. I stuff 20-something plants in there for winter.
 
 

Attachments

  • ow shelter 1.jpg
    ow shelter 1.jpg
    114.3 KB · Views: 64
Back
Top