wofati eco building

Another look at Simon Dale's Woodland Home in more detail.

I have a few questions regarding the "umbrella"

I was thinking of using 4in eps for insulation (it does make sense for me) and ldpe film as water/vapor barrier (maybe hdpe if i can find it) instead of pond liner due to the price tag.
Now these films don't come in huge sheets but they do come in rolls. One roll just might be 20ft wide, maybe.

1. How do you bond two films together if you have to ?
PE can be thermofused but you imagine the price for that.
If you overlap them by 3ft won't water eventually get in ?
I mean the only thing stopping that from happening is the sloping, 3ft vertical for 20ft horizontal.
Is that enough during heavy rains ?
Caulking won't stick to these films so it's just a temporary thing.

2. If you have heavy clay (vertisol) and moisture variations in it, won't the film break due to expansion/contraction ?

Oh, and this is on a flat land and with a regular house.

There is no glue that reliably bonds to polyethylene.

With a big overlap, you might get away with this:

Several beads of acoustic sealant (designed to stay sticky and flexible for decades, to seal seams in polyethylene vapor barrier), and the edges sealed with that super sticky (expensive) tape for sealing tyvek.


EPS is porous to water, compared to pink or blue high density foam, which is closed cell and very resistant to water intrusion.  I would hesitate to use EPS underground.

I am not an engineer.  You do this at your own risk.

Finest regards,

troy

I was thinking of sticky (expensive tape) but i'm unaware of any acoustic sealant. Do you have any suggestions for that (brand, chemical composition) ?

Regarding EPS, there are many flavors, well, really densities.
It's made for Compressive Resistance - at yield or 10% deformation of up to about 35 psi while XPS goes from 40 psi upwards.
35 psi is enough to hold a large 10 story concrete building on top, if the ground can take it.
The main difference between XPS and EPS regarding moisture intake is the behaviour in time.
35psi EPS has 2% intake while XPS has 1%.
However, the EPS value remains constant and insulative values are little affected.
For XPS however, the gasses used to create the closed cells during making will escape slowly and wil ultimately yield a somewhat larger value than for EPS.
Anyway, both are little affected by moisture but XPS is considerably pricier.

I found all this info somewhere i can't remember but it's easy searchable.

Anyway, if you look at whole foundation insulation you'll mainly see white foam (EPS) and very rarely colored foam (usually XPS but not allways) especially in small residential construction.

http://www.viking-house.ie/passive-house-foundations.html
scroll down to the pictures

http://www.aerobord.ie/products/insulation-products/floor/supergrund.html
http://passivehouse.ca/ph_tech_env_fnd.html
http://www.legalett.ca/Instproc.htm

You can use any of them as long as they are structurally adequate for the job.

I have no particular brand recommendations.

This site is pretty helpful:

http://www.inspectapedia.com/Energy/Acoustical_Sealants.htm


Yes, there are grades of xps that are approved and suitable for underground use.

Yes, they absorb more water than the extruded version.

Yes, xps is cheaper.


Practically speaking, if you have any significant ground water issues, like a high water table, you shouldn't be contemplating an "underground" umbrella house anyway.  But I expect you were fully aware and conversant about that.  From that point of view, the white stuff should be just as good, or nearly as good as the pink or blue extruded stuff.


My only reservation about xps is that I have seen xps in the field that didn't look so good after a decade, and the consequence of a failure is pretty significant.  I do NOT know if the xps failures that I have seen were properly spec'd in the first place...


Very interesting.

Please carry on.

troy

Paul presents on wofati eco buildings in this podcast: wofati podcast

I hope this thread is still alive... I have a question about the wofati house. Can Paul or anyone tell me about the flywheel effect of a big enough area of soil around and over the house? What I would like to know is whether it would be a dumb idea to have a layer of soy foam insulation on the outer side of the roof and walls, or would that seperate the house from the flywheel effect Paul was talking about? Would that even out the highs and lows or just remove the house from the flywheel effect altogether? I have a gut feeling the walls need to be in direct thermal contact with the dirt mass to get the benefits of thermal heat storage/cooling effects. Any thoughts?

Here is the first wofati sketchup. Geoff started off wanting it to be very authentic so he used sketchup logs for everything. I think that turned out to be rather CPU intensive.

We then started to add the newspaper and poly, and even a little dirt ....

And then decided to show that a different way.

This is an attempt to show the earthworks. Starting off with a hillside and the wofati shell.

and then a layer of poly and newspaper

Add dirt

another layer of poly and newspaper - this defines the umbrella

now add a thick layer of soil and vegetation

Here is a third attempt - this time starting with much simpler poles

Paul, there would be an uphill patio in these designs, right? Some of the earlier sketches show this, but the latest ones that you posted do not show an opening in the earth on the uphill side of the structure.

Yup, there must be an uphill patio.

Was already considered how much earth above poly would keep the voles, moles etc. away? I have land full of them, so I expect if I judge wrong and put to thin layer of soil on top, they will dig into my insulation and maybe find it as a nice living space. Does this happens? Maybe they won't cut pond liner? I doubt...

I was trying to figure out what you meant by above ground (it looks completely below ground in the book) and those photos helped a lot. thanks!

One of my concerns about Wofati design is managing moisture levels so they don't rot the woodwork.
I know, it's not supposed to have moisture - but that's a fantasy.
Moisture comes from inside as well as outside, and will roll down any impermeable surfaces unless carried away by ventilation. That means that any woodwork built up against the walls (like in the Underground House design) will rot sooner than exposed central woodwork, unless you're in an extremely dry climate or one mild enough to ventilate constantly.
Also, Murphy's law dictates that even a carefully-protected barrier membrane will probably get at least a few tears in it (through burrowing rodent action if nothing else).

I always want to see really old examples if possible, that have been proven in multiple locations, not just a 'good idea' that's been in place a dozen years and is doing great. Plenty of bad detailing can last that long.

I was excited to find a similar notion from a bygone age:
Viking Turf Houses

The re-creations are using plastic only for repairs/restoration. Traditional waterproofing is birchbark between two layers of soft, cushy soil - very similar to the cardboard-protected plastic idea. More birchbark is used on top of that if available, and the sod above acts like a kind of heavy windproof net to divert some of the water and hold everything in place.

Check out the wall drainage systems, air gaps for preserving timber, footings & drainage for the poles, and living walls - not just a sod roof, but sod 'fur' down the sides.

These are reputed to last about 30 years - might be more if they had access to decent birch-bark nowadays, or more practice laying and controlling the drainage.


The writer also says the 10th century version was much more comfortable than the 19th century Iceland turf houses - he's done overnights in both.
Ready to move in?


Turf isn't a common resource in dense woodlands, but is often available nearby.
This might work even better for the "wofati for the plains" thread.
Will cross-post.

-Erica W

Maybe this has already been mentioned but if you put some old screening between the layer of plastic against the sheathing, that would keep rodents out. I need to read over this whole wofati thing more cuz there are so many ideas. Did anyone actually build one?

came across this rather excellent video of a few Sami houses that sort of reminded me of wofatis because of the multiple layers of earth and wood that provided insulation.

there is also tons in the video about utilizing reindeer for many different things.

Thank you Cassie for this inspiration. That's what i was looking for, the tepee for the temperate, moist woodlands. I Love the shape and construction of the tepee for its ease and stability, but the cotton lining is just not suitable for wet climate, it rots very fast. The sami-version provides insulation with turf and a waterproof layer of birchbark, simple and effective.
I think of a slightly modernized version with windows, pondliner instead of birchbark and covered with soil... cheap and easy to build, can later be equipped with rmh.
Nice! Looking forward to build such a structure in springtime.

That's a cool video. I like how they came up with a design that uses the many small trees that grow way up north to make structures that stand up to snow load and wind. I really liked when she said that typically there would be more little branches left on the inside, to serve as hooks "for your wet socks" and such. Everything you have would smell like smoke, but that's not all bad. Like she said, they smoked their meat near the top of the "tipi."

One of my concerns about Wofati design is managing moisture levels so they don't rot the woodwork.
I know, it's not supposed to have moisture - but that's a fantasy.

I agree with Erica on this, and this is a serious concern. The placement of plastic directly on the wood members acts as a vapor barrier where you might not want it, and thus a place for water to condense (against your newspaper and your woodwork) in the Wofati design as Paul has indicated in his layers. The Viking Model indicates a layer of finer wood with spaces between them, and then a layer of duff, or sod, and then the birch bark before the final layer of sod. These spaces and layers add air flow between the main structural wood and the birch bark layer, thus keeping the main structural wood much drier.

In the video Cassie posted: Note the steepness of the roof of the Sami dwelling. Even with no sealant, the birchbark shingling is able to shed any moisture that penetrates the mossy sod or peat material that is used for insulation/protection. The birch bark is NOT a continuous impermeable layer such as is done by sheets of plastic, thus the shelter can stay dry and not have issues with condensation. Besides this, there is a hole in the roof to allow condensation a place to escape upwards.

In 2004, I lived in a Sami type dwelling in the late winter is South Central Utah, at the Boulder Outdoor Survival School, in Boulder Utah, when I arrived early before becoming an intern (wwoofer, basically) in exchange for a 28 day survival course (Which I highly recommend to those who are intrigued with primitive living). The shelter was not even layered with shingling, but was much heavier in duff/debris. No sod was used. The walls were about three feet thick, over top of the log tee pee. There was a central fire pit. There was also a gable entrance (similar to the downhill entrance of the wofati) on the structure so that heavy snows could fall without blocking the door. I don't know how they would open a sami structure door in the morning in the case of a heavy snowfall during the night. The entrance was a good place to hang extra gear and also to place extra fire wood. The smoke hole was not huge, but was adequate. A hot fire was necessary to create the initial draft, so that the structure did not fill with smoke. One of my wwoofer/intern jobs was to go up the mountain to a ponderosa forest with a pick up truck and go under the really big trees to gather tarp loads of pine needle duff to cover the structure with additional material.

I figured that the shelter could be improved on vastly with an external layers of bark (shingling), poles (structure), and duff (Insulation), as well as a possibly a clay rocket stove type set up, for more efficient fires.

Anybody interested in this type of living should really connect with the primitive skills community in the U.S.. Gatherings like Wintercount (South of Phoenix), Rabbitstick (near Rexburg Idaho), and Slickrock (at the BOSS basecamp in Boulder, Utah) all of which I have been to, are a great introduction to learning Earth centered skills. Other skills events are Earth's Echos, in Oregon; and in the south east, Rivercane, and Firefly. I haven't been to any of those other events. There are probably more.

I once too attended a course at an outdoor school, but in Germany. They had similar structures, a bit more "primitive", only made of poles and small branches all covered with soil, no extra barrier for moisture. A bit like a cave, half-open with a fireplace at the open side. Still absolutely rain-proof and very warm and comfy to sleep, but probably not very durable.
The more i think about it, the more i realize that the tepee-type structure is one of the most evolved and sophisticated designs for human shelter. The cone-shape provides excellent stability, the steep walls allow for fast water-runoff, it's easy to built wherever long poles are available, there are adapted types of this structure for winter, summer and different climate zones. Important element for a good function of this design is the fire in the center, since it dries out the structure (whether its cotton, buffalo hide or turf/bark) from the inside and helps the wood to dry frequently after getting moist. Smoke also adds to the durability of animal skin-covered shelter. Once abandoned, without fire burning daily, these structures will decompose very fast, as mentioned in the video, which is also a good function of that design. No deconstruction needed, just leave it and it will feed the soil.
In my opinion, a very permie-style type of building, which deserves further research and experiment for adaption to different climate zones and modern improvement, such as rmh's, windows, electricity etc.

paul wheaton wrote:So I'm combining a lot of ideas from a lot of people and coming to a new space amd I just need to express it.

First, we have

Sepp, building a shelter in a day: 

Total cost for the structure is about $1000 (two layers of felt and one layer of pond liner) plus the cost of the track-hoe.  Note that the soil is a meter deep over the structure.

And then we have Mike Oehler's designs that are in many ways similar - with light coming in all four directions.

Then add in the idea of the umbrella architecture:

(more details at http://www.norishouse.com/PAHS/UmbrellaHouse.html )

And a look I like:

(more at http://www.simondale.net/house/index.htm  )

I really like the idea that most of the materials come from the land. 

And I really like the idea that something can be built so quickly.

And I really like the idea that the structure requires little, if any, heating or cooling. 

And so I want to add to it a bit.  I want the roof layer to be like this:

12 inches wet soil
newspaper (half inch)
poly
newspaper (half inch)
straw/sawdust
newspaper (quarter inch)
8 inches of dry soil
newspaper (half inch)
poly
newspaper (half inch or more to get a smooth, even surface)
wood (2xX or logs)

So instead of double layers of pond liner/felt/insulation that is trucked in and costs about $8000, the total cost might be about $200.

Will it work? Am I brilliant? Or am I gonna die under eight tons of dirt? 

I'm getting the wofati umbrella bit by bit.  This picture is the clearest one for the ATI part!

Now I'm wondering about substitutes for the trackhoe for the trackhoe deficit problem situations...can a sledgehammer (operated by Thor) substitute?

If anyone has built a structure and is looking for ideas on how to test and replace a wooden post, here's a new video from Paul:

I've been reading this thread a lot lately - soaking up the info a little at a time.
But I still haven't seen any pictures or drawings of the uphill patio... There is one right?

Reason I'm asking, is I'd like to construct my own Wofati structure, and my mind's eye just can't envision the uphill patio...

have you read mike oehler's book?

paul wheaton wrote:have you read mike oehler's book?

Yes I sure have!! Started reading that far too many years ago to admit....
But I still have a rough time actually "seeing" the uphill patio.... it's a blind spot in my imagination.
Especially where he talks about covering it with the greenhouse corrugated material and using that to harvest rain water.... I 'get' the idea, just can't 'see' it.

Do these pictures help?

Thank you for the pictures - they are from the book.