Non-plastic umbrella for thermal mass

We are looking for alternatives to the petroleum based options, to have 20' of dry and warm earth around our house, without polluting the soil with nanoplastics.

Around the thermal mass, an open trench, for easier maintenance and microclimate creation, versus a french drain.

Between the trench and the house, sloped insulation and waterproofing, both buried a bit, so that the area is walkable and some plants grow.

Buried waterproofing options:
A) Curved arabic clay roofing tiles: due to gaps below them, and weight above them, they may crack. The soil above may cause overflooding of the tiles?
B) Flat clay roofing tiles: the soil above may cause overflooding of the tiles? Less than in the curved arabic tiles?
C) Roman opus signinum: crushed ceramic + lime in a continuous layer. Difficult to renew the insulation below.
D) Galvanized steel sheet: not durable enough?

Buried insulation options:
A) Sheep wool, unprocessed: free, insulates better when compress, manages well some humidity. Can last +8000 years if the conditions are perfect, but 1 year if wet. Better if the waterproofing above makes easy changing the wool every ¿5-20? years.
B) Arlite: durable. Does it have any polluting additive?
C) Mineral wool: it has petroleum based additives.

Thank you for your ideas and experiences.

Are you considering doing a variation of john Hait's annualized geothermal?  I'm just trying to make sure I am answering the question you are asking.

Could you bury a layer of expansive clay (e.g. bentonite) as the waterproof layer, then back fill with topsoil, or gravel or whatever, depending on your intended use, lay paving stones where needed, etc?  Roots could penetrate the clay layer, especially if trees are grown on it, but even deep rooted grasses, alfalfa, etc. might.  So, I think you'd want to be cognizant of that likelihood when planting.  But, the clay should be somewhat self-healing of minor penetrations, also.  Seasonal dryness of the subsoil at the waterproofing depth might lead to cracking, though.

Clay may not be the solution...

Thank you Kevin for your reply.

Yes, we want something similar to annualized geosolar, combined with a solar hypocaust (air radiant floor, see Living Energy Farm), to have more flexibility and avoid overheating the house in summer to store heat for the winter. A high water table and adjacent buildings also encourage this decision, because we can't create the umbrella all around.

Yes, the raw clay here is expansive and cracks. It cracks in the summer, so it's not a problem for the heating part, but may be a problem for the dryness and conservation of the insulation.

The idea is to plant shallow rooted plants above the umbrella.

Another option is to use Opus signinum in flat clay tile shape pieces, but it could be a lot of work to create them. ¿Maybe not so much work thinking in the long term? Maybe in bigger sizes...

Mikel Salazar wrote:Thank you Kevin for your reply.
...
Another option is to use Opus signinum in flat clay tile shape pieces, but it could be a lot of work to create them. ¿Maybe not so much work thinking in the long term? Maybe in bigger sizes...

You're welcome.  I am far from expert in these matters, especially in a permie way.  A decade or so ago, before I was properly acquainted with permies, I used expanded polystyrene and 6 mil poly sheeting to create an insulated and waterproof barrier around part of my basement, since we had "water features" every time it rained hard - old house with stone walls - and no drains.  I spent several furious evenings with a shop vac, sucking up water almost as fast as it came in, and hoping and praying for the rain to ease.  Desperate times, desperate measures.

I think the opus signinum would be a good choice, but I haven't yet experimented.  It's a form of what is now termed a geopolymer, and the lime should be self-healing of small cracks.  There are some broken bricks in a vacant lot near me, which would be prime candidates for such an experiment, but I don't know who owns them, so a bit of leg work on my part may be in order to discover at what price they might be had (hopefully free for the hauling!).  I also have a sack and a half of hydrated (steam slaked) lime, left over from when I tuck-pointed the sandstone wall of my dad's basement.  But, I have enough irons in the fire that I may not get to that experiment before snow falls.  In which case, the broken bricks will keep until spring, I'm sure.

From what I can gather, most of the AGS-like projects have used plastic sheeting or EPDM roofing membrane (or pond liner), and foam insulation.  It would be good to have a proven approach that doesn't require these plasticy materials.

You'd also mentioned a high water table.  Will you be berming the earth up around your house, somewhat of an "earth sheltered" approach, to avoid digging down near the water table?

I have a small piece of raw recreational land which also has a high water table (old beach dunes and swales, likely dating from the beginning of this interglacial, now many hundreds of meters back from the present lake shore).  I think the only reasonable way of building an Oehler or Hait greenhouse structure there would be to build on grade, then berm the sand up around and over the top of the building.  It might be possible to make a dome-like structure of a concrete like substance )perhaps opus signinum or similar) over the mass of sand, then cover the dome with sand, soil, etc.  But, I don't know if that's really practical.  I'd seen an attempt to pre-cast modular dome panels, then assemble them into a shell.  Also, a vault system which used interlocking blocks, which was quite interesting, but looked somewhat unwieldy, because the blocks had to be threaded over reinforcing rod which was about half the arc length of the vault section.  I don't think either of these really appeals to me, as interesting as they are.

I do have John Hait's monograph on creating concrete box sections, but they are proportioned and sized more-or-less like marine shipping containers.

Sorry for not being able to provide any real guidance on this.

Can you do a small scale experiment to prove out the opus signinum, before you "go for broke"?

From what I've read, the magic of the self-healing of cracks in lime mortars happens with quicklime, don't know about slaked lime. When adding ceramic, it should have been created with a lower temperature than modern ceramic, because some compounds crystallize at high temperatures and don't react chemically with the lime.

The plan is a 6-7' (2m) deep trench to lower the water table and send it to the river or pond, depending on the water needs. That way, we would have dry mass around the house. I understand that with a berm, the water would come from below it, similar to what happens in a keypoint of a keyline design.

I'm testing in a small area. Curved clay tiles looked as a bad option because of risk of cracking, over flooding... Next, I will try with flat clay tiles. Easy to get them and easy to remove them to check or change the insulation below. Let's see if they break when walking on the area. Next would be testing with opus signinum, in tiles bigger than commercial clay tiles or in a continuous layer.

If sheep wool doesn't work, expanded clay (called Arlite here) may be the choice. I would ask if it has any toxic additive.

They used to use clay on blackhouses and sheilings here in the Scottish highlands - a fairly constant wet environment though. I wonder whether you could cut clay with sand and/or earth (like making cob) and still have it waterproof but not crack?

I'm contemplating trying a thick layer of newspaper on the roof of my hobbit-forge. It wouldn't be fully dry, but would shed water I think.

Mikel Salazar wrote:
Buried waterproofing options:

D) Galvanized steel sheet: not durable enough?

At my work we have some rental mobile homes which are 40-50 years old. at some point in time they were roofed over with corrugated (galvanized) metal roofing. In the last year or 2 we have had to replace some roofing panels due to leaks and rust, likely because of collected leaves (&/or where a falling branch made a dent that holds water). Having seen that, I wouldn't expect treated metal to last more than a decade or 2 underground.

My initial thought was waxed canvas, or something similar, but I have no idea how that would hold up with earth contact.

Looking forward to seeing other replies; I'm hoping to build something similar in the future. I've assumed I'll need to use plastic (pond liner or similar), but being underground away from UV, I'd expect it to last the life of the building.

Flat clay tiles don't seem to be a good option. They don't lay flat on the ground as everyone must go a bit above the next tile downwards. That makes difficult to fully give them support below with compacted earth in stairs, and therefore the risk of fracture once buried is high, I think. Even doing that well, perfect even contact is impossible between 2 tiles. Therefore, stress points appear and breaks happen.

Burying sheep wool even makes thing more difficult: it should be packed tightly and evenly to prevent cracking tiles. That seems difficult to do it manually and with big pieces of wool. Maybe with compressed wool bales.

Continuous opus signinum above a layer of arlite could be the best choice?

 Continuous opus signinum above a layer of arlite could be the best choice?

What does this mean?

Don't know if you have access to it where you live, but how about birch bark? It's waterproof enough to make canoes out of, and three or more layers of overlapping sheets is a traditional moisture barrier in turf roofs. It doesn't really rot, but doesn't manage UV light well at all, much like plastic. Well covered by soil it can sometimes last very long. I've been wondering if you could improve its performance further if you combined it with clay somehow?

I feel like I mention birch bark a lot, but it is a wonderful material. We'll be using it as the moisture barrier in our turf roof. Haven't built the roof yet, but we did gather the bark. About a thousand sheets, now piled up, weighed down by bricks and protected from the light by a pile of spruce branches, waiting for next year.

John C Daley wrote:

 Continuous opus signinum above a layer of arlite could be the best choice?

What does this mean?

A layer of continuous (no tiles, no joints) opus signinum for waterproofing, above commercial expanded clay (called Arlite here) for durable insulation.

Eino Kenttä wrote:Don't know if you have access to it where you live, but how about birch bark? It's waterproof enough to make canoes out of, and three or more layers of overlapping sheets is a traditional moisture barrier in turf roofs. It doesn't really rot, but doesn't manage UV light well at all, much like plastic. Well covered by soil it can sometimes last very long. I've been wondering if you could improve its performance further if you combined it with clay somehow?

I feel like I mention birch bark a lot, but it is a wonderful material. We'll be using it as the moisture barrier in our turf roof. Haven't built the roof yet, but we did gather the bark. About a thousand sheets, now piled up, weighed down by bricks and protected from the light by a pile of spruce branches, waiting for next year.

Is this bark processed industrially or collected manually? How are joints managed? How does it behave with mechanical forces? It should be possible to put earth on it and then walk over both of them.

I've seen that they are developing natural waterproofing liquid products derived from birch and spruce.

I too, would like to know what is meant by Arlite?

Google tells me it could be several things.

Arlita, also called expanded clay, ripiolite, or LECA (Light Expanded Clay Aggregate), is a lightweight ceramic aggregate.

Don't know about how is manufactured for commercial purposes, but for scientific purposes I've read an experiment that created it adding sodium bicarbonate, acetic acid (like vinegar) and soap, to clay. That way, they create bubbles inside the clay that it's put in the oven.

John C Daley wrote:

 Continuous opus signinum above a layer of arlite could be the best choice?

What does this mean?

https://en.wikipedia.org/wiki/Opus_signinum

Opus signinum ('cocciopesto' in modern Italian) is a building material used in ancient Rome. It is a form of Roman concrete (opus caementicium), the main difference being the addition of small pieces of broken pot, including amphorae, tiles or brick, instead of other aggregates.[1] Its main advantage over opus caementicium was that it is waterproof, the reason for its widespread use in Roman baths, aqueducts, cisterns and any buildings involving water. In floors it provided damp-proofing.