Earthship Hybrid - seeking input as we plan this out.

Started by ListerD, June 25, 2008, 07:50:06 AM

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ListerD

We're getting close (next spring is when we plan to begin on the slab) to starting a build on our property and suddenly the ideas for the house have gone a different route than the original plan.

We're now debating a hybrid earthship. It would be cinder block construction (either bond or dry stack) for the N, E & W walls. The S wall would be 2x8 framing for the windows. SE & SW corners would contain the doors, wife would like small rollup doors (if we can screen them) or "dutch" doors to allow for clear breezes through the home coupled with clerestory windows.

The roof line we're thinking about is like this: http://blog.oregonlive.com/environment_impact/2008/04/solartwo.jpg

The inside of the N, E & W walls would be properly finished straw bale for insulation. The outside would be stucco to match the inside so the appearance is the same.

The rough idea is for 3 bays running North to South. West bay would be utilities/equipment, center bay is living area and the east bay is sleeping.

Now if I can figure out how to use some house plan software I'll try and get an image of it to post. I think I can do a rough drawing in paint or something.


Right now the main question is would the R value of the cinder block/straw bale be of sufficient values to make it worth it. Looking around the web and combining data from a couple sites I'm coming up with an R 54 wall but surely it can't be that high!
"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill

glenn kangiser

So this earth ship hybrid is entirely above ground?

The block walls would have very little R value, but the straw bales should be around R54.  That is correct.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

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ListerD

Yes above ground. In our area we're on top of a plateau and digging in or building a mound is too cost prohibitive.

We started researching alternative ideas a couple weeks back. Our original idea was based on one of the plans here and used as a dogtrot.

We liked what we saw in earthship design and it meets a lot of our goals. But due to physical limitations and time to build we almost ruled them out. But I decided to look at the approach I mentioned above since I'd seen a couple who used straw bale inside of a steel pole barn.

I'm going to try and draw out a (very) rough plan today but we're following the basic design ideas.

I want something that in effect could be opened up to nature during the more temperate times and closed off during the hotter and colder months with a maximum possible efficiency. Which is where my wifes idea for rollup doors (like garage doors) came from. Though I'm thinking about something more akin to the lifts they use on hangar doors.

I liked the idea of straw bale and since it's relatively easy to come by in our area it seemed pretty logical. But I have absolutely no experience with concrete or stucco, so I have a fair bit to learn.


I know technically you guys don't support the type of construction I'm planning but you've been a fountain of information as well as inspiration already.
"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill

glenn kangiser

I see the concrete block as being an unnecessary expense if you are not burming the house with dirt.

How about a pole structure or timber frame  like Stinks's and Drews  to the size you want then straw bales for infill and stucco outside , but with an added rain screen wall to make a safety for the straw bales. I would protect the bales with a vapor barrier -- with the screen wall something like Tyvek or Typar would be OK I think 2x4's flat on the outside of the bales, then stucco lath - the chicken wire backed with light tarpaper (common in rolls at Home Depot) attached to the outside of the 2x4 spacers.

Just an idea for you to think about.  The straw gives you the insulation of R54.  The concrete block only stops the earth from pressing on the bales if backfilled and burmed - no other added advantage that I can see.  Stucco is a bit frowned upon by strawbale purist, but as Drew and I discussed - it can be made to work without giving a problem to the strawbales.  Most homes around here have stucco rather than mud plaster.  Wide eaves are recommended and I add that the screen wall is highly recommended by me in areas with quite a bit of rain.  A crack in the stucco could give water an entry without it.  Fibermesh added to the stucco could help prevent cracking and add tons of strength at a pretty low cost.

We can teach you stucco.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

ListerD

Not quite sure I'm following you on the rain screen idea. Is this attached to the straw bale and under the stucco?

The ideas for the cinder block wall were (feel free to poke flaws):


  • Attachment points for future additions, screening, decking and etc. You obviously don't want to poke holes in a straw bale wall  ;)
  • Appearance that matches homes in our area.
  • Livable during construction. (We have to travel 900 miles round trip during construction).
  • Possible future burming should it become feasible at a later date.
  • In the event of a wall failure (leak/mold/rot) we'd still have a livable structure while repairs were made.


In the grand scheme it sounds as though that (the cinder block outer wall) would add a negligible cost of around $3k. Which is a lot for us but it seems as though it's good insurance and future proofing.

"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill


glenn kangiser

Yes - the rain screen just provides a place for water to drain away behind the outer wall but before it can get to the inner wall and damage anything like the strawbales.

If you like the blocks and they fit your plans I don't have anything against them -- I was just thinking of the added cost.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

Dustin

I have seen folks doing earthship-style houses with other materials, like concrete block, even tire bales. They all conform the basic rule, however- the north side is bermed into the ground. Otherwise, don't bother calling it an earthship.
You are going to lose a lot of earth tie (cooling and heating) by not following that basic rule. They are also high thermal mass homes with passive solar. Straw bale is not high thermal mass.

Go to "The Natural Home" to learn more. They pioneered the idea of using concrete block in a high thermal mass home that is essentially an earthship without the tires.
http://www.thenaturalhome.com/passivesolar.html

John Raabe

Yes, the term earthship refers to earth tempering and this works best in strong winter/summer climates where the earth temperature 3' down or so is close to a comfortable interior temp. (65-70). Then the soil can serve as a thermal flywheel.

When you build above ground with concrete block (which can be structural of course) you have some thermal mass but little insulation. You have to know your site and see if you can use that thermal mass to store solar heat. If not then there is little advantage to building with block as it can be expensive to insulate. The SunKit on the CP plans page will let you evaluate the solar on your specific site and determine your best themal mass for the climate your in.

Strawbale can be good insulation but is time and labor intensive. It also has to have another structural system such as timber framing. Standard framing is the option most folks take between good insulation, good strength, easy modification and relative cost considerations (including long term maintenance and resale).
None of us are as smart as all of us.

ListerD

OK, so maybe I should've made the word Hybrid more clear  8) ;) I chose earthship because most people are familiar with the term and the system packages involved. The things we're taking from the Earthship concept is water reuse, open bay format, solar gain and the natural planters inside and out along the south window wall and more. Essentially everything BUT the earth tie.

Arguably you could say we'll have an earth tie in the sense that our air intake(s) from the outside (during the hottest and coldest seasons) will be buried 9' underground and have roughly a 60' run underground to balance the air temp.  :-* But that doesn't quite fit the concept I know. As I said above, eventually we may actually be able to berm it in on the north side which would be more inline with the concept (reasons for the block are above as well). To dig down on our property to build a house would be too cost prohibitive. So we're planning to build above ground and berm it in later if possible.

As for thermal mass, we have in mind several storage masses including a seasonal trombe wall, stone floors and etc. I'm looking more towards insulative factor to retain heating and cooling rather than earth mass to obtain it. This place will be grid tied for a few years so we have time to incorporate more effective systems in the future, but if we start well insulated we're half way there. (ack! I hope that made sense)

In our case we're looking for the highest possible R value we can squeeze out of natural building materials. So the straw seems to be the best choice, but we're always looking which is why I came here since there's a lot of solid and skilled brain pans to pick. I'm open to everything that's said.

We had a solar survey done last year, I'll have to find the results. This resulted in us moving our planned building site nearly 400' farther south on our property to give us the best possible winter coverage.
"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill


John Raabe

What climate are you building in, and what are the soils like? Well drained, clay, gravel, etc.

It sounds like you have a good solar site. Are you getting good winter sun as well?
None of us are as smart as all of us.

ListerD

John,

It's typical mid-Ozarks climate. Are you asking general averages? If so:

Summers are usually 85-90 average and humidity is usually high. Though last summer we had a few very low humidity days that reminded me of the desert.

Winters are usually in the 38-40 degree range. But it does get cold, there were a few days this year down around 20 while we were down.

You can check here: http://www.crh.noaa.gov/sgf/?n=records_normals

The soil is heavy clay, sand and rock mix, great graze land but poor for gardening (unless you want a rock garden! 8) ). This photo sums it all up:



The build site drains well as we sit the highest on our little plateau. Heh, it all runs to the neighbors place. Keeps his pond full, so "our" surface water will keep him in fish! ;D

Winter sun was great at the new selected build site this year, might have to remove a tree or two on the south east corner. I didn't think the survey was right but we stayed there a couple times this winter and it beams right in where the survey said.
"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill

John Raabe

Thanks for that - it is always helpful to understand the climate folks are in.

You're in a mostly heating climate with maybe a little cooling help in the summer. Winters are relatively mild and you are far enough south for a decent sunpath through the sky to provide usable light. It sounds like soil and drainage should not be big issues. Building on slightly higher ground is always advantageous.

Solar is something you can definitely take advantage of but savings and returns will not be as dramatic as if you were in the high country of the desert Southwest.
None of us are as smart as all of us.

ListerD

QuoteNone of us are as smart as all of us.

HAH! That's exactly why I'm here. Never noticed your signature before.

The only negative to the area (IMHO) is the trailer and unkempt property up on the corner of our road. Our neighbors to the east are fantastic! The ground as far as a garden is easily worked around via raised beds.

OK, I'll try and get a drawing together this weekend. I may do it on paper and then scan it in first. I am no architect so please don't expect perfection.  d*

The floor plan we loved is actually from Dustin's link. I'd been there plenty of times. Rather than embed the image into this post, here's the link directly to it: http://www.thenaturalhome.com/floorplana1.jpg


I guess our concern in this manner is just the fact of a low R wall vs a high thermal mass. It seems to make more sense to me to adapt it, starting with high R value insulation and then add thermal mass in the form of stone planters, flooring and trombe walls. It's difficult to go back and add R value to an established home but easy (in this type of design) to add thermal mass.

Clarification anyone?
"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill

John Raabe

I agree. The first principal for a home in all but the most ideal conditions is to insulate the shell well. That means all 6 sides. Then you can add thermal mass and south glazing to that environment and the stored heat and "coolth" will be able to make a difference.

So, in general, you want to insulate on the outside of thermal storage materials.

But, be advised, your climate may not justify high cost high mass strategies such as trombe walls. They certainly aren't justified (and don't work!) in my cloudy winter climate. Insulated direct gain slab floors do, however (and you get to use the SF to live on!)
None of us are as smart as all of us.


ListerD

#14
Trombe wall comment noted.

This weekend we'll sit down and discuss how much square footage we really need. I know it's probably going to need to be about 1600 sq. feet but I'm sure there's got to be a minimum/maximum for the solar gain to be at an equilibrium. Maybe I'm remembering it wrong, but I remember reading something about something about size vs. effectiveness, too small was too hot and too big was too hot (based on design characteristics).


Another question: In the hottest of seasons you still need the sunlight (in the design option I posted above) for your plants. How do you keep that heat in the planter area and not have it circulate into the house? I know you need something like in a greenhouse where you vent it out on the end walls by the glass wall (edit: just read this comment on the HTM site). Obviously some will be brought into the house and then up and out the clerestory, how do you deal with the rest of it? I know we could put throw rugs down onto the slab in those areas to slow/stop the thermal mass from gaining too much.

"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill

John Raabe

#15
You will want to decide early on how much you want to LIVE in a greenhouse with the plants vs having an attached greenhouse you can SHARE with the house.

Glenn may have some thoughts on this as his may be more integrated.

For myself, I have an attached, unheated sunroom that is thermally uncoupled from the house by an insulated window wall. When too hot or too cold we close the doors and windows between the two. In spring, fall and winter when the sunroom has extra heat we open up this wall. With passive vents the sunroom is never more than 10ยบ above outdoor air temperature.

Solar Saltbox.
None of us are as smart as all of us.

glenn kangiser

We have pretty wide eaves on the south but hte sun really shoots in there in the winter.

Our greenhouse is above the uphill patio to prevent rain from entering the high side of the house fo it's a bit different than you would think of as a normal sunroom. 

We have successfully experimented with a solar powered fan to send the heat down below, but we don't really need it -- lots of waste wood on the property that needs to be cleaned up anyway.  We only need about 1 1/2 cord per year anyway.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

ListerD

So we sat down this weekend and looked at size and etc. Having moped around measuring and marking off spaces in the wifes family barn we came up with 1600-2000 sq ft. This depends a lot on our future package (i.e. children and home business). 1600 is the definite low end and 2000 is the high.

I do keep running the greenhouse through my head. I *love* the idea of the planters in the house so that our most common veggies and herbs are right there, we get the partial air filtration by the plants and the house would seem more alive and natural as well. - the heat poses some questions in my mind but the screening recommended on the Natural Home site is something I'm already familiar with and it does work fairly well. (Here is where I need to hear from others who have built this way - is it effective and what is your climate compared to ours in Missouri?)

Another question came up - I like the idea of the "earth tubes" recommended on the Natural Home site, and the fact that he's used smooth wall pipes that can be cleaned. Has anyone done this?


General construction question - with a monolithic slab, how do you account for water drainage in the even of a leak? I should add that my idea of monolithic slab is just that - solid slab no penetration through it like drains. Maybe my definition is different than that of the real world ;) ;)

As far as insulation, he's recommending EPS which makes sense but it's not a natural material. He also mentions straw bale but this poses a question - IF you were to use straw bale against the outside of the SBC block, how do you seal the "inside" of the straw bale? i.e. what's against the brick. I can see that as being a condensation point in a high humidity environment.

"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill

glenn kangiser

Earth tubes cool warm air causing the moisture it is carrying to condense and fall out.  I would say to have the entrance high as the warm air will cool ad get heavier - then make a way to drain condensation off at the low end of the tubes which is also the air exit end.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

ListerD

SO while reading this morning I came across this and had to post it... Must be some FANTASTIC engineering!

QuoteThermal control membrane (TCM), a multi-layered metalized film membrane and is our latest patented energy conservation product.  TCM is simply rolled out over your existing insulation which changes the direction of heat. Out during the summer and in during the winter.  Unlike other single layer reflective membranes, TCM  is impervious to gravity, dust or settling.

??? :o ???
"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill


John Raabe

Sounds like the old reinvention of "reflective barrier" insulation. Each new energy crisis seems to have a marketer who reinvents this quick fix solution that someone (the government, the building industry) is trying to suppress.

This time the miraculous membrane has acquired anti-gravity properties!

Ain't technology wonderful! :D
None of us are as smart as all of us.

ListerD

#21
Heh, yeah there's a lot of smoke and mirrors in the building industry particularly when it comes to energy savings. Not saying their product is... but it certainly doesn't defy gravity!  ;D

We've picked the rough floor plan and will base it on this one: http://www.thenaturalhome.com/floorplana.jpg  This will give us roughly 2300 sq feet, a little more than we wanted but it's a very workable plan and we did want a relatively open plan.

Next question, we don't want to waste the trees for purlins, would rather season it and mill down for finish work and furniture. I saw a wooden I-beam at the big box store the other day, it was made from a 2x4 top and bottom and chip board as the middle part of the beam. I like the idea and it's a good use of "scrap" to make the chip board. There's a concern between my wife and I about the glues used. i.e. they may contain formaldehyde. Anyone have any experience with these?



It looked like this but I think the board was larger top and bottom, like I said more like a 2x4.
"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill

glenn kangiser

QuoteEngineered wood products also have some disadvantages:

    * They require more primary energy for their manufacture than solid lumber.
    * The required adhesives may be toxic. A concern with some resins is the release of formaldehyde in the finished product, often seen with urea-formaldehyde bonded products.
    * Cutting and otherwise working with engineered wood products can expose workers to toxic constituents.

The types of adhesives used in engineered wood include:

    * Urea-formaldehyde resins, (UF), most common and cheapest, not waterproof.
    * Phenol-formaldehyde resins, (PF), a yellow-brown adhesive commonly used for exterior exposure products.
    * Melamine-formaldehyde resin, (MF) a white, heat and water resistant resin, often used in exposed surfaces in more costly designs.
    * Methylene diphenyl diisocyanate (MDI) or polyurethane resins which are expensive and generally waterproof do not contain formaldehyde.

A more inclusive term is "structural composites". For example, fiber cement siding is made of cement and wood fiber, while cement board is a low density cement panel, often with added resin, faced with fiberglass mesh. Plastic extrusion mixes of wood fiber and thermoplastic, such as polyproplyene, has given rise to decking and railing material resistant to weather and is steadily replacing rot resistant wood.

http://en.wikipedia.org/wiki/Engineered_wood
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

ListerD

ack!  :o

I know PF outgasses relatively quickly but I guess there's no real way of knowing what is in the beams.

OK, so if we went that route does anyone have a glue recommendation? Obviously this is something that can be site built.

Any other beam suggestions? Flat roof with about a 25 degree pitch, minimal snow load (rarely get snow, but do get ice storms), 16 - 18' span.

Commercial/industrial look is fine since part of our design idea is sort of an "Earth meets Man" goal.
"We shape our dwellings, and afterwards our dwellings shape us" -- Winston Churchill

mvk

Hi
Interesting project. I'm not so sure that you can build those on site so easy. I think with your spans solid lumber would work for about the same money. You can build other kinds of trusses on site pretty easy if you don't have to worry about inspection or if it's OK with them.

What kind of insulation value are you looking for and what were you thinking of using? What do you want for a ceiling? If you were thinking of some type of window wall for your greenhouse that could work pretty easy with a post, beam, purloin, plank ceiling. That would work with rigid insulation and a metal roof.

I have thought of using those industrial re-bar trusses for a house, I think if you like industrial they could be pretty [cool]! Painted with light from your light tubes bouncing around. Guess they must coast a fortune now with the price of steel, (Ceiling? metal?) maybe if you could get the trusses used.

John is on to something about the greenhouse/sunspace. Living space, heating, and greenhouse don't all add up to the same thing. When you optimise one you minimize the others kinda of. They had some anti-gravity greenhouse's way back, I built one 8) in 1978! I would make sure that I understood what I was doing with any mass inside my house.

I'm having some trouble with getting what I want in a small enough footprint. I want a big pantry, laundry room, full bath and half bath as well as a good size bedroom with closets tacked on to a living/dining/kitchen space that's big enough to have 5 or 6 couples over. Think 12 geezer's with chubby checker singing "Twist baby Twist" and all the furniture pushed back, or a 2 table poker party.

Anyway I'm thinking of placing my dinning room in a thermally isolated sun space and space heating it when I had to. Ideally I could hinge a bunch of sliding glass door panels together maybe on piano hinges and open up the the room. I would love to capture all the excess heat and store it but I want to keep it simple too.

And if you have wood to burn what Glen said trumps all heating considerations.

I'm also looking into the glues there are a lot of people that are trying to build with out or with as little of the glues and stuff. I'm not real hung up on it but if it's all the same I would like to keep them out.

Mike