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Mike's passive solar greenhouse design/build

 
Posts: 140
Location: Washington DC area (zone 7a)
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@Mike, think about how you might be able to repurpose the space before demolishing it -- you might be able to make that space into something like a planting station and storage or something.  That said, it still might be better to rip it out and use it for a more beneficial purpose.  I had made a mistake like that on my own project and regret it to this day, but that is a LONG and preferably private story for offline.
 
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Mike Haasl wrote:.

I also picked up ginger and turmeric from our organic food store and have them tucked around in the beds.  We've saved all our pineapple tops and have many of them started as well.  I also realized that the piper nigrum seeds look remarkably like peppercorns.  Since none of the purchased ones came up, I planted about 50 peppercorns in the beds.  Hopefully at least one will grow.  Lastly, I found a vanilla orchid at the local greenhouse/florist and brought that home.

[/list]



I think I'm a bit jealous about these that you are attempting.  I've heard black pepper takes awhile to sprout. Ive gotten several pineapple to get growing but not to fruition. And OMG a real vanilla orchid? Are you kidding me?  I want to try this eventually but know I will have to have a greenhouse to attempt properly.

Please DO keep us updated on everything greenhouse!
 
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From the top posting: One or both sides will get shredded hay mixed in to increase the Nitrogen ratio.

People should be aware that farmers growing hay use a spray application of a chemical that will even go through a cow's system and still be toxic to plants.

Make sure that your source for hay does not use chemicals (I've forgotten the name for the common chemical they use), but that the crop has NOT been sprayed with chemicals. That chemical is very, very detrimental to plants. IF in doubt ask your source people to verify that the hay is herbicide free.

Had to stop and check on that name. It is Grazon, however, that is only 1 of 3 main herbicides that are commonly used.

BUYER  BEWARE !!!
 
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Boy have I been delinquent in updating this thread.  Sorry about that!

I removed the compost bin.  Related to Jesse's concerns, I ended up using garden clean up materials for the "greens" instead of hay.  It didn't work.  When removing the bin I left the platform above it in place and supported it with a post and beam.  That eliminated catwalk modifications and the whole job was much easier:




The biggest project for the summer was building an Active Heat Battery.  I don't have it running just yet but should soon.  I know that system won't keep the greenhouse above freezing but it might keep the minimum temp at 25 instead of 20.  

I will rig up a temporary internal greenhouse under the platform for this winter to keep the potted plants alive one more year.  I have room to plant one or two of them in the ground around the edge of the temporary greenhouse (by the banana).  So in future years I might have a couple citrus in the ground, a winter warm area and the rest of the greenhouse will just have to handle going a bit below freezing.  Time to get some plants that can handle a touch of freezing.  

This summer I had a huge butternut squash volunteer covering about 400 square feet, carrots, jalapenos, a tomato, passion fruit, swiss chard, birdhouse gourds and snap peas growing.  Peppers once again had horrible aphids so I think those aren't destined to survive in my greenhouse.  The carrots are about ready to be harvested as are the butternuts.  I transplanted some kale from the garden and it's doing well.  

I need to get better at growing food in this greenhouse.  I've been in a bit of a holding pattern waiting to see if I can keep it above freezing.  Time to just move on and pick other tree/shrub crops that can live in it.  
Chunky-butternut-squash.jpg
Chunky butternut squash
Chunky butternut squash
 
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I think the curved design is great - both for strength and to allow more light inside.  Also for shedding snow.  If you would please darken the handwritten lettering in your diagram it would make it so much easier to read your drawing.  
 
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Location: Currently located in central OK. Farmstead location is in northern VT.
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I'm working on some cold climate greenhouse designs myself. I would love to know how this turned out.
 
Mike Haasl
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Good point, it's time for an update!

I've given up the idea of compost heat (within the greenhouse).  The way I did it did not lead to any appreciable heat but it did give off gasses that made me wonder if they were healthy.

I put in the Active Heat battery system (per the above update) but neglected to protect it well enough for a cold night (12 degrees lower than forecast) and the radiator split open.  I soldered it up a week ago and it's now ready for action.  But then I found that it would take a tremendous amount of antifreeze to keep the system from freezing at 20F.  

So my current plan is to move the heat battery into the area where the compost pile was.  That area is also closed off as a mini greenhouse for the tropical plants.  With a tiny electric heater.  So the barrels of water will stay above freezing in there.  I finally figured out if I reroute the heat collection piping I can keep all the liquid within the mini greenhouse and avoid any antifreeze.  But it will take more work to implement so that might not happen before the coldest part of winter is past.

This week is going to be pretty cold (-20F at night and 0F for daily highs) so I'll see how cold the greenhouse gets at night without the moveable insulation.  My guess is around 20F.

I'm planning to plant trees in the ground in the greenhouse this summer.  Figs, peach, pawpaw, almonds, etc.  And also use the greenhouse to extend my growing season.  I struggle mightily with aphids on peppers so I haven't done well with them the last two years.

I could elaborate, what are you interested in Patrick?
 
Patrick Edwards
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Mike Haasl wrote:Good point, it's time for an update!

I've given up the idea of compost heat (within the greenhouse).  The way I did it did not lead to any appreciable heat but it did give off gasses that made me wonder if they were healthy.

I put in the Active Heat battery system (per the above update) but neglected to protect it well enough for a cold night (12 degrees lower than forecast) and the radiator split open.  I soldered it up a week ago and it's now ready for action.  But then I found that it would take a tremendous amount of antifreeze to keep the system from freezing at 20F.  

So my current plan is to move the heat battery into the area where the compost pile was.  That area is also closed off as a mini greenhouse for the tropical plants.  With a tiny electric heater.  So the barrels of water will stay above freezing in there.  I finally figured out if I reroute the heat collection piping I can keep all the liquid within the mini greenhouse and avoid any antifreeze.  But it will take more work to implement so that might not happen before the coldest part of winter is past.

This week is going to be pretty cold (-20F at night and 0F for daily highs) so I'll see how cold the greenhouse gets at night without the moveable insulation.  My guess is around 20F.

I'm planning to plant trees in the ground in the greenhouse this summer.  Figs, peach, pawpaw, almonds, etc.  And also use the greenhouse to extend my growing season.  I struggle mightily with aphids on peppers so I haven't done well with them the last two years.

I could elaborate, what are you interested in Patrick?



How much luck are you having with the tropicals?

I have been contemplating some designs for an attached greenhouse in a very similar climate. I would like it to be as low energy use as possible as our place is off the grid. So as much passive heating and insulation as I can muster would be the thing. So my current plan is a vertical style greenhouse kind of like the attached example (although attached to the south side of the house). The version I had in mind is a bit taller and sunken down to below the frost line as well (so about 40"). Reflective insulation on the inside of the side walls and the inwardly angled top portion of the back wall. The rest of the back wall would be painted a dark matte black. I was going to utilize a scattering of dark rocks as well as the black rain barrels on the north side of the wall. It will have be a vertically layered situation. For the "windows", I was thinking corrugated polycarbonate or some real heavy clear plastic for the outside layer, with a couple of additional layers of 6 mil plastic sheeting behind it. So 3 layers (heavy duty on the outside) with maybe about a .5" gap between them. There is also a small pond that would be just outside of the greenhouse area. So I was considering ways to bring that inside of the greenhouse a bit. A neighbor has a trout hatchery and I am hoping to utilize the pond to irrigate the greenhouse somewhat for a small aquaponics sort of setup. We are also going to utilize the Chinese greenhouse blanket over the 'windows' at night thing. If all that fails to keep a moderate enough temperature, which it probably will when it is hitting -20 to -30f, I was also thinking about some radiant heating from a wood boiler. Either an exterior boiler or from the boiler attached to the wood stove. Although the latter is also being used for showers, cleaning, probably radiators, etc. so more likely an additional small external boiler somewhere. Anyway, all these thoughts are hypotheticals. We won't start building the greenhouse until much later this year at the best. Next year is more likely. I am just trying to get a good plan in order for a really super efficient greenhouse. The goal is to be able to use this one to grow plants that need more warmth year round. It would be awesome to get squash and tomatoes in the winter still. We are going to build a more standard high tunnel sort of deal a little further off from the house as well but that is going to be mostly just for getting things started and for veggies that are far more cold tolerant.  I'll have to sketch something up at some point to make all that more clear but I would love to hear your experiences with some of this stuff and your thoughts.
figure1.jpg
[Thumbnail for figure1.jpg]
 
Mike Haasl
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Well, the tropicals are surviving.  I'm sure a real grower would have them in much better shape than I do.  I got 7 lemons this year though...  

I think the biggest struggle for folks in our climate is temperature (lows and highs) and sunlight.  With the photo you attached, especially if it's taller, it will heat up really well on a sunny day.  Mine can easily hit 100F inside on a sunny January day when it's 0 outside.  So the smaller the volume and the greater the exposure to the sun, the worse the problem could be.  Plants that are barely making it through the night at 40F don't seem to like it that warm.

I'm sure mine would do better if I could plant them in the ground.  This year I will also plant my lemons and maybe another citrus right at the edge of my mini greenhouse.  Then they can have roots in the ground, can be in decent sun in the summer and yet I can wrap them into the mini greenhouse and help them survive winter.  I should take some photos of the mini greenhouse set up...

With sinking down 40", don't forget the pile of snow that will also be on that south wall.  With low angle sun and no snow, you may not get sunlight to the floor in winter.  With 4' of snow piled at the base of the glazing, the sun is blocked for much of the growing area.

Black is good for absorbing heat.  White is good for reflecting light to the plants.  I went with white but there are many ways of thinking.  I avoided the barrels of water painted black mainly because I thought they'd be in the shade of the avocado trees all the time.  No sun on barrels = less heat storage.

Layers of poly and plastic sound good to me.  If you have the twin wall poly on the outside it should stay flattish.  The poly will sag as it heats up but in your case it would sag away from the poly maintaining an air gap.  Two layers of poly may sag and touch or the inner one may sag more and it'll be fine.  Limiting light with that many layers could be a problem.  I believe they make 5x polycarbonate panels.

If you can do the Chinese Greenhouse blanket you could skip some of the poly layers.  A good insulated blanket would really help the situation on cold nights.

Regarding the pond...  If the pond is inside and connected to the pond outside, I think it would sap away a lot of heat.  And be hard to build a foundation in that area.  A pond totally inside should work.

Squash and tomatoes might hold their fruit into winter but I'm thinking you'd need to add light to keep them fruiting past October.  Maybe I'm wrong, I don't really know.

Good luck!
 
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Your greenhouse sounds amazing. Yes it gets pretty cloudy and dreary in the winter and spring. I have a fig, and a lemon tree in pots and I bring it inside the house overwinter. I also have lemon grass and a bay tree.
 
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I live in a similar climate and was planning a heat tubes system with off-the-shelf greenhouse, with insulated walls/ceiling, and walls that roll up for summer.

What factors in your design contributed most to the heat? and were cost effective?

E.g.

Horizontal insulating panels in the ground does not seem that useful because:  

"the total heat reaching the surface of the Earth of (1.8+0.0000058) = 1.8000058 watts/cm^2, only 0.0000058/1.8 = 0.0003% is contributed by the Earth's internal heat. This, of course, will dominate everything else if the Sun were to magically vanish!" - Source: Nasa

I dont have compost material, and prefer low management.



Cost:

"Phase change materials" - like glycerin cost $500 for 55 gallon barrel, so the net effect on temperature needs to be justified, whether 1 drum of glycerin or 10.


Etc....  There were a lot of moving parts, several which were not real clear from a non-engineer/builder.  

If your system did not stay above freezing at night (got lost in really long thread), or if I want to have a more tropical solution, I am thinking to combine with heat tubes.
 
Mike Haasl
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The biggest contribution to heat is definitely the sun.  The biggest loss is the glazing.  Leakage is minimal with my design but it's probably the next biggest loss.  I feel pretty good about the foundation insulation.  I don't follow your watts/cm2 comment though, could you elaborate?

I don't think the compost provided much help and it did generate gasses and odors at times that had me worry.  The moveable insulation seems to give me 10 degrees of help on cold winter nights but it's a pain to deal with in the manner I implemented it.  

I haven't done the glycerin but if I did I was going to try to find a biodiesel maker who might have it as a waste product.

I am trying to collect heat off the ceiling and blow it through a radiator to store heat for the night time.  Hopefully I'll have results this winter.

I passed on the earth tubes since I was aiming for more heat generation at night than I believe they can provide in my climate.  Since it's cloudy 80% of my November and December, earth tubes would only be drawing from the deep earth temperature.  Here that's in the low 40s.  It's hard to do much heating when your heater is putting out 40 degree air.

This winter I didn't bother with the insulation and on our coldest night (-29F) it got down to +9 in the greenhouse.
 
Ebo David
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@pete, the foundation insulation essentially creates extra thermal mass similar to barrels of liquid, phase change materials, or thick solid walls above ground.  Without any thermal mass the temperatures swing wildly.  Take a look at some of Shannon Mutschelknaus' greenhouse design inspired by U. Minnesota's Deep Winter Greenhouse:

Intro to Passive Solar Greenhouses: Session 1 <https://www.youtube.com/watch?v=BI7Br7XcTs4&list=WL&index=30&t=2022s>;

Intro to Passive Solar Greenhouses: Session 2 <https://www.youtube.com/watch?v=MzuhkbzSqEA&list=WL&index=29&t=4743s>;

He did a little thermodynamics modeling and found how the heat transfer differed with and without wings, as well as insulation thicknesses.  His foundations are only 4' deep (I was actually expecting more), and his earth tubes are at 4' and 2'.  BTW, his place is in central South Dakota, and it gets COLD there...  Anyway, I hope you find his examples useful.
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