Walipini Greenhouses up North

I was researching greenhouse styles that would support the growth of citrus plants in Northern climates. I came upon this article regarding in ground greenhouses. In the article, the author states that "it’s possible to grow sub-tropical plants without an additional heat source in regions where sub-zero temperatures are common". -> http://www.realworldsurvivor.com/2013/10/28/underground-greenhouses/#geogreenhouse2

I live in zone 4 NH. Obviously, there are many ways to build a walipini greenhouse... what building strategies would you recommend for building a greenhouse that maintains 50-60' temps seen in the article? The Ott-Kimm Conservatory boasts a zone 8 micro-climate in a zone 4 area. They dug 5 feet below the ground’s surface, and poured 6-inch-thick reinforced concrete walls. Would this be a good baseline? Citrus plants can grow to zone 8, so technically they would be able to grow in a greenhouse that replicates a zone 8 climate (according to this article).

Opinions? What do you think?

If it were possible to keep the greenhouse at 50', would black soldier fly larvae be able to hibernate there overwinter?

Going into the ground in colder climates is a good idea. The walipini was designed for tropical high-altitude climates and does a wonderful job -- there. There are several underground/sunken greenhouse plans available that are suitable for higher (northern and southern) latitudes. The Oehler underground greenhouse is one of them.

I would recommend insulating the north facing roof of the greenhouse (put reflective surface underneath), as well as over the ground around the perimeter, at least 5 feet (umbrella homes go out at least 20 feet).

Another interesting option is using geothermal with earth(air) tubes or more conventional water tubes and a heat exchanger.

If you can work out a system to easily (if it isn't easy, it tends not to get done after awhile) cover the glazing with insulation at night and sunless days, you can keep the heat loss even lower.

An airlock entry is also a good way to minimize heat loss. It is especially important if you have a staircase or ramp leading down from the outside to the floor of the greenhouse.

Three is a guy, ldsprepper, on YouTube that built a pvc hoop house that uses earth tubes to stabilize temperatures. He says he gets temperatures about 20 degrees warmer inside the greenhouse, but when the temps drop below about 15 F (and where he is, -15 F is not uncommon), you can still freeze plants at night. He is installing insulation on his north facing wall to reduce heat losses, and putting in a heater to keep his plants from freezing. Even without supplemental heat, he is able to extend his growing season substantially. He also uses the earth tubes to cool the greenhouse in summer, and it can get very sunny and hot where he is.

So, for citrus, I would consider a heavily insulated above-ground greenhouse with earth tubes, or a sunken greenhouse (with or without earth tubes) with a minimum 5' insulated apron and insulation on any above-ground north-facing surfaces, and an insulated curtain or shutter. A lot depends on the site, costs, and availability of skilled workmen and material (shipping costs can be a deal breaker). Supplemental heat would be a must, to insure survival through the most bitter cold and sunless winters. You may also need supplemental lighting if you experience a lot of winter fog.

Wallipini only really works in high latitudes if it's built into the side of a south-facing hill. A true hole-style wallipini shades most of the growing area most of the day during the darker half of the year.

Here's my two cents: Passive solar, earth integrated, heavily insulated north wall, north roof, and insulate the sill down at least 5' below ground and all the way up to the glazing in zone 4 with a minimum of 2' tall frost wall , insulated curtain (insulated blankets used in concrete construction work great) for night time, with earth tubes as intake ventilation through large compost piles inside greenhouse to buffer and heat up incoming air. Air lock (double door with space in between doors so one can be closed before the other is opened). As extensive a "climate battery" as possible. Rocket mass heater and/or sauna built into large mass north wall. Use RMH as the winter exhaust port with a solar powered fan, so as to "soak up" as much of the solar generated heat as possible into the mass. Oh yeah LOTS of low albedo mass: soil, cob, stone, concrete, water(best) placed where it can receive maximum solar gain . Also if you want inside temps and co2 levels to stay high integrate mammals into the mix, just design your structure so the hot moist animal air goes through a biofilter bed to absorb the excess ammonia from the manure (especially important with bird droppings). Not only can mammals produce copius amounts of co2, a mammal generates 8 btu/ hour/ pound! Also make sure your perimeter drainage is really, really good, wet ground surrounding the structure will drastically reduce insulating capacity. Also think about radiant heating loops with water set into the floor that can be heated with solar and wood. People are doing great things building the foundation and mass with earth bags filled with the excavated material and then stuccoed over. Use High R value, High E value glass where ever possible with shade system for summer. Twin or triple wall polycarbonate is the next best choice and it is a lot lighter than glass and just as strong saving money on structure cost. Devil is in the details: design a structure that is easy to make airtight, and make sure all the water details (ie gutters, sill drain, flashing ect.) are designed and installed correctly. Think about designing roof and walls so if there is any condensation in can be collected via indoor gutter systems to a cistern. Also it is very important to design cold sinks inside the greenhouse so the cold air has somewhere to sink to besides around your plants, I have seen peoples plans to incorporate a root cellar into the lowest cold sink of the structure. All I can think of right now...

Sacha,

Entirely possible given the right thermal storage. Many have done so, but they do incorporate lots of thermal mass or thermal storage. Rather than earth tubes, look into an "earth to air heat exchanger" (alternate search names, GAHT system or climate battery) which stores the heat of the greenhouse in the soil underground. Several other factors are needed.

The base model for a walipini does not work at northern latitudes given the low slope of the glazing. You want to pursue an "earth sheltered greenhouse" (see Mike Oehler's book) which has earth berms around the sides. I wrote a blog comparing these two at ceres greenhouses, ceresgs.com

Good resources -- CRMPI (new book out on their methods) and Ceres Greenhouses.

That should be a start to plenty more research, but in short... where there's a will there's a way.

Lindsey Schiller wrote:
Rather than earth tubes, look into an "earth to air heat exchanger" (alternate search names, GAHT system or climate battery) which stores the heat of the greenhouse in the soil underground.

Semantics. They are, essentially, the same thing. You could include in your search the terms: earth battery and low-grade geothermal. YouTube has many sunken/underground/earth sheltered greenhouse ideas, as well as various geothermal/earth battery options.

Compost heat is another good option. I am not sure having it, and animals, in the greenhouse would be good year-round, especially if you get high summer temperatures and/or a lot of sun. You could have it, and animals, in an adjoining structure. Availability of biomass to feed the compost pile may be a limiting factor in some areas. This video was recently posted in the Compost section of Permies.

It is often quicker and, ultimately, cheaper to purchase someone else's expertise, so I am in no way seeking to detract from what Lindsey is offering.

Andrew Parker wrote:

Lindsey Schiller wrote:
Rather than earth tubes, look into an "earth to air heat exchanger" (alternate search names, GAHT system or climate battery) which stores the heat of the greenhouse in the soil underground.

Semantics. They are, essentially, the same thing. You could include in your search the terms: earth battery and low-grade geothermal. YouTube has many sunken/underground/earth sheltered greenhouse ideas, as well as various geothermal/earth battery options.

Compost heat is another good option. I am not sure having it, and animals, in the greenhouse would be good year-round, especially if you get high summer temperatures and/or a lot of sun. You could have it, and animals, in an adjoining structure. Availability of biomass to feed the compost pile may be a limiting factor in some areas. This video was recently posted in the Compost section of Permies.

It is often quicker and, ultimately, cheaper to purchase someone else's expertise, so I am in no way seeking to detract from what Lindsey is offering.

-I suggested both a GAHT ("climate battery") system and an earth tube intake system-They are NOT essentially the same thing- A GAHT system is recirculating air within the greenhouse, the earth tube intake is the intake for fresh air into the greenhouse- without animals, compost, fermentation, or fungal decomposition generating co2 you will need to exchange the air within the greenhouse, the earth tubes buffer the intake air temperature then having the air warmed up further by directing through hot compost pile then through a biofilter (porus high carbon soil grow beds) to reduce ammonia gas then into the grow space.

-And I suggested a biofilter between the compost/animals and the growing area, not putting them in the growing area- often a great choice (when feasible) is to have an earth sheltered barn as the north room of the greenhouse seperated by thermal mass and air circulated between the growing space and the barn space through a biofilter.
check out Justus Walker's post on his ambitious plan to build an earth sheltered greenhouse in siberia: https://permies.com/t/32195/greenhouses/Wonderful-AMAZING-News-Earth-Sheltered

And check out Anna Edey's greenhouse designs for other cool ideas.

Tyler Omand wrote:

They are NOT essentially the same thing

Hmmm. So, an earth tube is a large plastic pipe buried deep in the dirt with air drawn through it whose temperature is then moderated by the stable temperature of the dirt at depth; while a GAHT is a large plastic pipe buried deep in the dirt with air drawn through it whose temperature is then moderated by the stable temperature of the dirt at depth. The only difference being that one may be a closed system and the other an open system. I understand each new author's desire for original/proprietary nomenclature, but wouldn't it be less confusing to differentiate by simply calling one an open earth tube system and the other a closed earth tube system?

- Why would one need to run the air moving through a large plastic pipe, that has passed through a compost pile, into a biofilter? If you are using perforated pipe for the system, wouldn't it be less complicated to use solid pipe for the section that passes through the compost pile?

- Ammonia can be controlled by using charcoal (biochar) in the bedding and spraying the bedding with probiotics regularly. Animals don't like ammonia in their eyes, noses and lungs and will be much healthier and happier if ammonia is controlled in their living area.


- Mike, I like the reuse of the patio doors. Very frugal. Since they are in the same area, I wonder how it compares to ldsprepper's hoop house, as far as cost and temperatures?

Better results might be obtained if the berm was thicker, compacted and insulated. Gabions could be used as retaining walls for the thicker berm. Insulating an apron/umbrella around the structure, from 5' to 20' out would help to isolate the soil surrounding the greenhouse for better heat retention. Running heating coils in the insulated berm and the insulated soil to take in heat from the solar panels during the summer will raise the average soil temperature under insulation.

Earth tubes could also be installed to moderate air temperatures, particularly in the summer, since the solar panels are already providing a lot of supplemental heat. Evaporative cooling works pretty well in dry climates, but it uses a lot of water, so if summer temps in the greenhouse can be kept in the optimum range without resorting to evaporative coolers, it would be more sustainable.