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the first wofati greenhouse design

 
master steward
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I need a thread so people can make their design suggestions.
 
paul wheaton
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this came in through my email:

Many problems I see with your kickstarter idea. I have been dwelling the past several months on a much bigger idea, yet much smaller as well.

Here's my take so far on what I'm trying to research the idea for.

A fireproof, rustproof, rotproof, rustproof, insectproof, rodentproof, waterproof, hopefully fireproof and bulletproof all in one house which heats itself, provides its own water and hopefully even(still a long ways off on this) provide its own source of power(non solar, wind, or hydro). Everything will be contained in a structure which is secure, not a homestead but a securestead.

My idea as it currently stands, it keeps on evolving all the time into something much better:

Fiberglass structure, no wood(wood burns) and very little to no metal(rusts). The fiberglass is waterproof and can be structural enough when used with regular sheet insulation to make it so you can make non standard walls(not vertical but slanted walls).

This is a small house, under 32 sq ft, no permit necessary and no property tax assessment.

The bottom level will have an air gap between the ground and the floor of the compost pile/house. The air gap prevent any worries about radon gas(5-6 miles north of where I live is known for uranium deposits).

The compost pile will sit with a lightly insulated fiberglass housing. It will have a door on one side for removable of compost and also to let the heat out during the summer months.

Above the compost pile will be storage space, probably 2-3 feet thick, this is closet space for the house right above it.

Right above the storage area will be the main room of the house, no walls. other than the outside walls which both inside and outside are made of fiberglass with R50-60 insulation between them. The outer wall would be much thicker than the inner wall. The heavy insulation is for both keeping the house warm but also to make sure the heat wants to move one direction only, upwards.

The walls of the house turn lean outward at an angle. The angled walls are used for both shade against the walls to keep the UV light down, since UV likes to break down fiberglass, but the angled walls also help to create more garden space up on the roof. of the house. The angled walls also make it harder to try to climb the walls to get to the door into the house which is on the roof.

There are no windows in the walls, and the front door is also not in the walls. This makes it difficult for someone to break in and steal anything or take any of your food unless they bring a nice big ladder with them so they can get up on the roof. Being built out of fiberglass it won't burn as easy as it would if was built out of wood. Also by being built out of fiberglass you aren't limited to the confines for insulation like you are with wood and you don't have the heat loss due to the wood interrupting the insulation in the walls.

On top of the house you have the rooftop garden which can be covered like a standard greenhouse. Only now it is protected from prying thieves due to it being up on top of the house. You have quick easy access to it while in the house since you go right by it every time you come or go from house since the front door is up on the roof. You need to manufacture a quick release/quick(small) storage ladder scenario so you can easily remove the ladder and take it with you anytime you leave. This further protects the house and greenhouse/garden from thieves, and animals.

Down in the compost pile you have a tank, which receives all liquid waste from the house this liquid waste gets heated up and rises up into the house and recondenses into fresh drinking water. At the same time a pipe through the floor/storage area which goes down into the compost pile receives all your shit for the compost pile/wastewater tank.

Everything is compact in design and the flow of everything works the way it is supposed to and gets rid of all the complex plumbing and heating problems associated with standard houses today.

The heat from the compost pile rises to heat the house. The heat from the compost pile warms the grey water tank and causes it form condensation which also rises into the house where it recondenses into fresh water. The heat from the house continues to rise to the ceiling(still not sure how much insulation I would want in the ceiling given the rooftop garden). Once the heat from the house leaves the ceiling it warms the rooftop garden which is also helping to insulate the structure underneath it. Now put a simple greenhouse on top and you should have close to a year round greenhouse out of reach of most people and animals. The only trouble would be providing enough sunlight during the winter months to keep anything growing all winter long.

This is a day and age where protection is far more important than having an item. You can have a car but if you have no electricity or gas supply, what good is the car to you. You can have the garden/greenhouse but if your neighbors/rioters/looters can come and take everything from it and leave you with nothing--than what good is it?

The biggest problem with your design shown on the kickstarter page is the simple fact of it sitting partially buried in the ground. That leaves it totally unprotected from troublemakers, which there are plenty of anymore, with many more being added each day. Your design needs a secure method of protecting the garden/greenhouse or what is the point of building it in the first place? You can't make a point of the idea being feasible if everybody has stolen all the food from the greenhouse.

Remember your old forum posting about cutting your heat bill by 87%. Why not get rid of it entirely. The trouble with your way of approaching it is space. Space is the dumbest frontier, not the final frontier. The more space you have the more it takes to heat up the space. I have lived in a 468 sq ft shack for 20 years now but stumbled into the tiny house concept back in '13 or '14. I trimmed my living/heating space down to 48 sq ft and wrapped the 6 walls with R60 pink panther insulation. I spent a couple of years in that room before shrinking it on down to 32 sq ft and lived in it for two years. Both years included R30 in the ceiling with the second year also including R30 in the floor. Last summer thanks to your 87% posting I shrank the room down to around 50 cubic ft with R60 completely surrounding the room. Unfortunately I didn't get the chance to try the room out this past winter since right after finishing the room I moved in and started full time caretaking for a friend of mine. I've been hoping to completely get a setup made where I could 100% eliminate the heating bill other than body heat and stray electricity from lights and a laptop computer. Typically during the summer months I only use 4-6 Kw /month, aka laptop and light. I need to get rid of the heating bill 100% and then I'm doing pretty good, but not until then.

I think the idea I'm looking at now is far more along the lines of what I'm hopingto accomplish with a lot of side benefits to it as well since I live with plenty of deer which love to eat the garden. I also have tons of mosquitoes and I have recently heard of the possibility of getting rid of the mosquitoes by moving everything up off the ground. I hear they don't like it much above 5-6 feet above ground. If I could garden or sit outside on a nice summer day and enjoy without having to deal with the bugs, because I'm above them then I win.

Still not sure about the electric generation but I am thinking something along the lines of using the evaporating/condensing water cycle for it, not sure how I could though with such limited production.  Everything, in this day and age, needs to be completely self-contained and secure or else you have nothing.

 
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Interesting project. I am concerned about the deep hole. Someone is bound to drop their car keys inside. So there has to be a maintenance ladder of some sort which leads to the likelihood of a soil collapse when someone is investigating the sudden dampness at the bottom. Will the walls be braced?
 
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It sounds a lot like living in an inground pool.
A living space sandwiched between an active compost pile and a working greenhouse sounds rather uncomfortable .
The material choice seem incompatible with previous design choices.
The security concerns might be personal.

I do like the idea of a compost pile beneath the working green house, but I can't see how it can work passively long term.
Maybe a Solvia style vermiculture filter could work,  it is said the early if ever need emptying.
 
William Bronson
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My own idea concerning a the green house project is related to walls and shoring,  etc.
Maybe leave the internal wall sloped rather than vertical.
Most soil will slump into a naturally dictated angle if it isn't reinforced.
When we berm above ground  walls we are using this to our advantage.
We could dig a slopped walled hole with a flat bottom, tamp the soil and cover these "walls" as we normally would in a WOFATI
There the will be very little pressure against the wood and sheeting of the wall.
Build bleachers on this slope and grow in containers sitting on the bleachers.
This is especially good for hand dug holes, because less soil needs to be removed yet it is a safer hole to be in.

If we dig a strait sided hole maybe we can still use an internal berm.
Build your walls as usual but add a layer of sheeting to protect the wood from your internal berm.
This sandwich of plastic and wood could be a problem,  but not necessarily.
Borox or wood ash could be applied to the wall to help stave off decay.
In any case, berming against this wall gives more support for the wall.
We can build this berm as we like,  layering in drain tile, hugel materials, earth tubes, PEX loops,  geofabric , biodigesters, rainbarrels, rocket stove bells or whatever.
When we have built the berm to within a two feet of the top of the wall,   we stop.
Against the top of the wall we set diagonal braces that parallel the surface of the berm.
In addition to bracing the wall,  they also offer support for a layer of glazing, insulating or pest exclusion material that will sit about 2 feet from the surface of the berm.
By laying a board across the bracing,  we can lean in and lay   within 2 feet of the berm surface, for harvesting,  planting and weeding.

Any of these berm ideas could be used above ground,  but the key is to berm on both sides of a wall, the wall itself being less structural support and more a form for the earthworks.

 
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Thoughts to kick around:  

I understand the 5' pit under the walkway from an evolutionary design perspective, but with the 20' pipes do you really need that pit or is it just vestigial?  It means a lot more digging and materials as well as a future hazard if the walkway should give.  The air in the greenhouse will likely be humid which could lead to rot at some point years down the line and an unexpected 5' drop could make for a really bad day(s).  Being lazy, I also like not digging/building it.  I suspect that you could have the walkway over perhaps a 6" deep bottom that is sloped to the pipes so that the cold air would just drop into the walkway and down into the pipes while eliminating the future hazard.  When I was thinking about something like this I was actually thinking of just having a gravel floor (perhaps mildly sloped to the pipe openings) at the bottom of the walkway with cast drain grates over the pipe openings to let air in and out, but not keys or what not.  I was also thinking that the beds to either side of the walkway pit would be sloped towards it such that cold air drains into the walkway volume, and then into the pipes.  I think sloping the beds towards the walkway also may make them easier to work with when standing in the walkway.
 
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My design suggestion is to massively increase the surface area between the deep soil and the greenhouse interior.  Much like Travis Johnson's idea about keeping stock tanks from freezing in Maine with a Geothermal Culvert.  He uses a 10' length of 15" culvert to passively allow warmish deep earth temps to come up under his stock tanks.  

I'm suspecting one (or 5) of these in the cold sink, or in the place of the cold sink, could really make a difference.

It would be really nifty if there was a way to connect two of them at the bottom and then encourage the air to travel down one and up the other.  Maybe if one end was in the cold sink and the other was higher and in the sunlight?  During the day the sun hitting the culvert might make the air want to rise?  At night with the coldest air settling into the cold sink it might want to push down into that culvert and help slightly warmer air come up through the other duct.  A similar concept could be done with clay chimney liners but connecting them at the bottom (safely) may be a challenge.

The attached crude sketch is the view from the south looking into the greenhouse.

With any underground tubing, I think we can learn a lot from the Citrus in the Snow and the CRIMPI approaches.  They have fans and TONS of ductwork in contact with deeper soil.  This application is completely different but it's worth keeping in mind the scale of what they need to do to harvest heat from soil.  Many many many square feet of surface area.  With forced air movement.
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A second grader could do better than this artwork
A second grader could do better than this artwork
 
Edward Lye
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I read this book about the construction of China's railway line to Tibet. "Methods included using pipes called thermosiphons along the sides of the tracks to refrigerate vulnerable parts of the soil along the highest parts of the plateau, an area that comprises the largest continuous sub-Arctic permafrost region on the planet. These cooling sticks are 7.6-meter-long steel tubes drilled into the soil; they contain ammonia, which draws latent heat out of the soil as it evaporates. " Might this be an alternative to that hole/trench? It has no moving parts.
 
Greg Martin
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Edward Lye wrote:I read this book about the construction of China's railway line to Tibet. "Methods included using pipes called thermosiphons along the sides of the tracks to refrigerate vulnerable parts of the soil along the highest parts of the plateau, an area that comprises the largest continuous sub-Arctic permafrost region on the planet. These cooling sticks are 7.6-meter-long steel tubes drilled into the soil; they contain ammonia, which draws latent heat out of the soil as it evaporates. " Might this be an alternative to that hole/trench? It has no moving parts.


So it sounds like their thermosyphons are a form of heat pipe?  Heat pipes utilize gas phases to very rapidly move heat in the vapor phase from a warm source and deliver the heat to the cold spots by condensing into liquid, which delivers the heat through the phase changes.  If ammonia were to leak it would kill you, so another fluid would be desirable, but one that works at the right temps.  The CRIMPI system relies on water vapor to deliver the heat to the earth battery, which provides the added benefit of dehumidifying the greenhouse air.  Using water is very attractive.  For example, you could channel water down the inside glazing at night into a rain gutter that would deliver it back down into one of the pipes.  Since this system is a greywater treatment system their should be a good supply of water into the system to make up for any lost to the deeper ground.  Paying close attention to the water cycling in this system would be a VERY good idea as it may be critical to the efficiency of the system.  I'd very highly recommend using sensors that measure and log both temperature and humidity in the key locations of the system to understand how it's really moving heat.
 
Greg Martin
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Alternatively you can capture the water and send it back to the house for reuse, creating a loop of water to the house, greywater to the greenhouse.
 
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I don't understand how the thermosiphon works to cool the greenhouse.  A bit of air is in the hot part of the tube, it gets heated up to so that it is hotter and less dense than the air outside the top of the tube so it moves up and out.  The bit of air behind it is siphoned up but it wouldn't move up and out of the tube until it is hotter and denser than the air outside the top of the tube.  So it would only work to heat the air.

Does it need to be shaped like an upside down J?  Maybe you wouldn't get the siphon part without gravity pulling the cooler denser air out of the tube.
 
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Mike Haasl wrote:My design suggestion is to massively increase the surface area between the deep soil and the greenhouse interior.  



That is my thought as well.  I don't think a 1 or 2 or 3" pipe is going to move enough air to do much.  I read Mike's greenhouse book years ago.  My first thought was, what if the cold pit was 30 or 40 feet deep instead?  I understand the safety issues involved.  It still seems to me that having the area underground much larger than the greenhouse itself would be necessary.  I'm not an engineer though, so I could be way off base.
 
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I wonder if you've heard of Tim Meyers of Bethel Alaska? He had greenhouses working in Alaska, and if I remember correctly from what I read back in 2009, used compost heat kind of like this, (not Tim Meyers)  


NPR on Tim Meyers https://www.npr.org/sections/thesalt/2015/02/26/389011370/alaska-farmer-turns-icy-patch-of-tundra-into-a-breadbasket

Update on local public radio in 2019, https://www.alaskapublic.org/2019/10/08/bethels-meyers-farm-shuts-down-market-focuses-on-internet-sales/

Direct link to Meyers Farm, http://meyersfarm.net/
 
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Mike Haasl wrote:With any underground tubing, I think we can learn a lot from the Citrus in the Snow and the CRIMPI approaches.  They have fans and TONS of ductwork in contact with deeper soil.  This application is completely different but it's worth keeping in mind the scale of what they need to do to harvest heat from soil.  Many many many square feet of surface area.  With forced air movement.


I hate to sound pessimistic but I’ve watched dozens of YouTube videos about heating greenhouses this way, and they all point to the need for a lot of surface area and a lot of air flow. In John Hait’s book Passive Annual Heat Storage the main factors seem to be moisture control, massive storage/heat tubing, good air flow, and heat retention (insulation). The concept itself is sound. I’ve discovered that with zone 3 winter it takes about r60 to keep the ground from freezing. I now have a greenhouse which doesn’t freeze, but is still not warm enough to grow anything between November and March. As Mike mentions, extensive tubing either deep down or under an insulated umbrella, plus good air flow, is key to having sufficient warmth to overcome the heat loss that will occur at the glazing. Multiple layers of glazing would help. Elliot Coleman grew winter greenhouse crops in Maine using multiple glazing- essentially a cold frame in a double glazed greenhouse.
I think the ultimate success of this Wofati greenhouse project may not even be whether it works as designed, but the resulting conversations, brainstorming and further experimentation that occur around it.
 
pollinator
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Love this idea!!!  Is there a link we can use to put on Facebook or other sites to let people know abou this?   And thanks for offering so much at even the 1 dollar level.  Even if someone didn't want the greenhouse moive, That is a prize in itself.   I think this is one of the best greenhouse Ideas I have seen, I just want it connected to or a part of a Wofati house.  
Sorry I should have read the whole email and then I would have know .... so disreqard my question about a link.  
 
Julie Reed
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Kyle Bob wrote:I don't understand how the thermosiphon works to cool the greenhouse.



Good point! I don’t think this system as currently conceived will do that. To cool, you need a stack that exits at the highest point, so the hot air is exhausted, drawing cooler air up from below. But that does nothing to charge the mass. Paul says in the Kickstarter that “When the sun hits the greenhouse, the pipe would pull cold air from the bottom. Eventually the hot air at the top of the greenhouse would be pulled into the trench and warm the trench.” I see that as extremely optimistic. Hot air by nature has no interest in falling. It takes effort to force it to sink, more than just air flowing passively. I don’t think cold air being pulled up will pull hot air down. In fact, even if the tube was an inverted “J”, for air to return to the trench (passively) it would need to be colder than the air in the trench. It seems, as Kyle describes, more like a cycle of warming cooler air with hotter air, creating more warm air overall. Somehow that hotter air needs to be returned to the mass all summer, if you want to charge it up for the winter. I’m also not seeing that in this design.
That said, I don’t think the mass, if kept dry and properly insulated, would need to be charged to accomplish success here. It’s part of a larger mass (the earth around and below) and will likely maintain 50 degrees year round, given how small the greenhouse is in comparison. And it’s easy enough to get excess heat out in the summer with a vent and wax filled cylinder to open and close it.
 
Edward Lye
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Looking at the roof, what if a few Cybetruckers get lost and decide to drive up to the roof to get their bearings and enjoy the view? Would the "roof" collapse? So a fence with the warning "Danger! Loose Earth." would be in order or a fake radio antenna mast with guy ropes all around. I still don't like the trench. If lost hikers seek shelter there and the earth then decides to give way ... . A locked door would be unfriendly. There is a guy who who makes earthships. He said one of his designs had too many windows and everything inside overheated even when snowbound. An outdoor curtain perhaps? Just some more food for thought.
 
Mike Haasl
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Kyle Bob wrote:I don't understand how the thermosiphon works to cool the greenhouse.  


I think the idea of the original thermsiphon is to dig one well casing hole and get the air to move in and out of it in a way that helps the greenhouse out.  So a 6" casing with a smaller pipe inside could conceivably do that.  If you can get the air to want to move up or down in the smaller pipe.  I can see how if the sun is hitting the small pipe, it would heat up the air inside and make it want to rise.  If it did rise, something has to replace it and the coldest air in the greenhouse is in the cold sink which is where the larger pipe's opening is.  So maybe the cold air will drop down into the well casing as the smaller hot pipe draws air out the top.

I don't know what would happen at night.  No sun on the small pipe.  Greenhouse flirting with 35 degrees.  Well casing sitting at 50 degrees.  The air in the casing would want to rise but it needs cold air to fall past it down the casing.  Or down the small pipe.  Or up the small pipe and down the large one.  In any case, I'm not sure it would move any air at night.

I think a wofati greenhouse at Allerton Abbey with no well casing at all would probably go below freezing at night in the depth of winter.  I'll guess 25-30 degrees for the low.  I suspect that the thermosiphon won't really change that.  BUT it's worth trying!  Turn it on and off to prove if it works or not.

I think a wofati greenhouse at Allerton Abbey with a 40' deep cold sink would probably stay above freezing at night in the depth of winter.  I'll guess 35-40 degrees for the low.  That is based on the vast majority of the greenhouse's interior surface being in contact with warmer soil as compared to the little bit in contact with frozen glass or a door.  The more surface area against the "warm" soil, the more balanced out the temperatures will be day to night and summer to winter.

A 40' cold sink isn't practical but large culverts might be.  They'd certainly be safer.

With the deep cold sink or culvert idea, I'm not expecting to "charge" the mass at all.  Just use the thermal energy in the ground.
 
Mike Haasl
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Another idea for consideration:

If increasing the contact area of the greenhouse with the subsoil is a good idea...  How about adding culverts or a man-made tunnel system like shown below?  Culverts could horizontally exist the cold sink and go back into the mass.  They'd be connected to additional culverts that connect up to the back wall.  I doubt air would flow in one and out the other but they'd still have the effect of buffering the temps in the greenhouse by significantly increasing the surface area.  
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Great place to lose a cat
Great place to lose a cat
 
Edward Lye
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Greg Martin wrote:
So it sounds like their thermosyphons are a form of heat pipe?  Heat pipes utilize gas phases to very rapidly move heat in the vapor phase from a warm source and deliver the heat to the cold spots by condensing into liquid, which delivers the heat through the phase changes.  If ammonia were to leak it would kill you, so another fluid would be desirable, but one that works at the right temps.  The CRIMPI system relies on water vapor to deliver the heat to the earth battery, which provides the added benefit of dehumidifying the greenhouse air.  Using water is very attractive.  For example, you could channel water down the inside glazing at night into a rain gutter that would deliver it back down into one of the pipes.  Since this system is a greywater treatment system their should be a good supply of water into the system to make up for any lost to the deeper ground.  Paying close attention to the water cycling in this system would be a VERY good idea as it may be critical to the efficiency of the system.  I'd very highly recommend using sensors that measure and log both temperature and humidity in the key locations of the system to understand how it's really moving heat.



https://www.arrow.com/en/research-and-events/articles/how-does-a-thermosiphon-work explains the differences between a heat pipe and the thermosiphon and claims a superior performance. Basically we want the earth heat wen the interior is cold and to heat the earth when the interior is warm. Either way we have a temperature differential to drive a circulation with a couple of check valves. Ultimately the best solution is a superconducting rod which has the property that the temperature throughout the rod is exactly the same temperature. Again no moving parts.
 
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