The Greenhouse of the Future ebook by Francis Gendron
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Sarah Tennant

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since May 02, 2021
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Recent posts by Sarah Tennant

Aha! I know someone must have thought of it before I did. :p Good to know - thanks! I kind of like the idea of using the top of a cable spool, cut in half, as shutters.
1 month ago
People sell or give away glass topped tables pretty often, and on some of them the glass just sits in a metal frame and can be easily removed.

Any reason this wouldn't work for window glass? It wouldn't be double-glazed, obviously, but I was thinking if you had two you could put one at each end of a wide windowsill (such as in an earthbag or cob house, with thick walls), have both the indoor and outdoor part operable, and use the space in the middle to grow pot plants or whatever.

1 month ago
This is probably a silly question, but I can't find an answer. Will straight earthbag walls be stabilised by the timber framework, or will they still need buttresses? If so, you can use internal earthbag walls as buttresses, right?
2 months ago
What if I used an earthen plaster on the interior walls, so the earthbags could breathe that way?

I've seen a method of earthbag construction where the earthen plaster is applied at the same time as the earthbags are laid (like, a few people are laying higher courses while other people start throwing mud on the lower courses. The idea is that even though the bags have to cure, leaving the other side of the bags unplastered for a few months allows the moisture to escape that way, so it doesn't matter that the plaster's applied 'too soon' on the first side.

By the same logic, even if the earthbags couldn't breathe against the spray-foam insulation, if they could breathe against the interior earth plaster, wouldn't that be fine? Obviously we would cure them before applying at least one of the layers.

My current thinking is that I like the look, cost, DIY-ability and thermal mass of earthbags, but am worried about their lack of insulative properties. I'm pricing up bulk pumice, but I suspect it'd be too expensive to use to fill the bags. (Haven't priced up scoria yet, but again, I suspect where I live it wouldn't be financially feasible; likewise vermiculite, and I don't think we could even get rice hulls here at all.)

So if I could do earthbag walls and spray insulation over the outside, and then cover that (quickly, so it wouldn't be exposed to heat and light for too long) in plaster/stucco, possible with a stone facade for the bottom few feet... well, that could work well. Assuming it does, uh, work at all.
2 months ago
I have a vague memory of reading somewhere that foam insulation could be sprayed on the outside of an earthbag house.

Does anyone know how (or if) this would work? Could you stucco over the insulation? Would it have to be a natural earthen stucco, or a concrete-type one, or would either work? Would the foam insulation breathe, expand and contract appropriately, etc?
2 months ago
I read the three-years rule on some article about cordwood building, but you're right - since then I've found people saying you only need to leave it for a year, and a few even saying less time than that.

The offcuts would be treated for in-ground use, so I assume it'd be pretty hardcore preservatives. Good point about the earthen plaster not containing any toxins.

Probably a bad idea, then. A shame - it seems like a very readily available waste resource.
2 months ago
We're looking at natural building alternatives and I considered cordwood, but even if we found land with a lot of trees to cut down, seasoning the wood for three years isn't really feasible.

But where I live people are always selling cheaply, or even giving away, timber pile offcuts from house foundations. They're round and the right size.

Any thoughts? Obviously they're treated, which would make them more rot-resistant but less natural (but then, we would completely enclose them in plaster/cob/whatever anyway, as we don't like the exposed ends look).
2 months ago
Thanks, that's really useful info! Do you happen to know if the composition of the fabric makes any difference in terms of longevity? My guess is that even organic fabric will be essentially fossilized by the concrete and won't decompose any faster than synthetics (so, not at all, I guess!), but I don't know for sure.
2 months ago
Ooh, further thought: as an alternative to the curved guttering thing, you could scallop the edges of the carpet to make a cute vaguely thatchy pattern. On a gypsy caravan that'd be pretty cute, admit it.

I wonder if you could even stack layers of carpet to get that scalloped-top look some thatched roofs have? Or would that be adding too much weight to the top of the arch?

Most of the ferrocement cloth roofs I've seen have been, in my view, unattractive, largely because they really look too thin and drapey and cloth-like. It doesn't smoothly undulate over supports, it shows every ridge and pole of the underlying structure. It's like wearing a skirt directly over hoop skirts without having all the layers of petticoats in between - the 'bones' of the hoops show through awkwardly.

I'm hoping the thicker and less drapey carpet, combined with the closer mesh of the hog panels, would mitigate those problems and make the whole thing look smoother and sturdier.

I do actually like the idea of drapey roofs though,  especially over dormer windows and such. I reckon you could get a really storybook-cottage vibe if you were careful. I wonder if there's a much thicker fabric that would work? Could you sandwich a ton of old wool blankets? Would the cement prevent them from decomposing over time?
2 months ago
Say you had a narrowish rectangular structure - think shipping container, gypsy caravan, shepherd's hut, that sort of thing.

Could you roof it by curving galvanised hog panels over the top, attaching them with staples or something to the outsides of the walls; then covering the panels with old carpet, and then soaking it in a few layers of cement, ie. ferrocement?

I feel like this could be cute - you could even curl the carpet up at the broad ends to make a kind of inbuilt guttering, and angle it downward towards a downspout or whatever.

But also, I have no idea what I'm doing and it might be a ghastly idea. :p Thoughts?
2 months ago