Glenn Herbert wrote: threshing always involved beating up the stalks.
Glenn Herbert wrote: Do you have any thoughts on how to keep straws in compression lengthwise from buckling?
Glenn Herbert wrote:I had a feeling you were heading to wheat paste glue
What is the strength of that in tension (how well will it hold the straws together), and how long will it last in a building context? What moisture content can it absorb before weakening? How do you keep insects etc. from burrowing in it and eating it? Borax??
I understand that straw is valued in cob building in part because it is mostly fiber with little digestible matter. Wheat paste is highly digestible.
Brainstorming is wonderful, but the concept needs some elementary testing to determine some actual values. Can you get some materials to do it? I hope you do really investigate this, to either find that it is viable or find another way of using the material that works better.
Glenn Herbert wrote:Light straw-clay is recommended to be not more than 12" thick, so that it can dry out before mold sets in (also recommended to be built in dry weather). The possibility of internal molding needs to be investigated... is it an issue or not? Would building up the dome in layers mitigate the issue sufficiently? There are lots of factors to investigate... how soon can a stock of undamaged straw be available for use in testing?
Something occurred to me in regard to durability: I have seen talk of adding lime to strawbale plasters. Would it help to have a wheat paste/lime mix? The lime is said to increase rigidity and preserve straw to some degree. I expect you would need something like lime plaster on exteriors near the ground, even if you add a thatched roof layer. It would need to have overhanging eaves so water is directed away from the walls at ground level. You would obviously also want plaster on the interiors.
Glenn Herbert wrote:Straw, like bamboo, has joints, so air would not be able to flow through the stalks regardless of end sealing. I would expect the glue, if it was sufficient to secure the stalks, to also block many of the ends as well. Not to mention that you are talking about the straw all being oriented parallel to the vault surfaces, so there would be nowhere for air to go if it could travel through individual stalks.
Max Kennedy wrote:Though all true, for building purposes hemp would be better. Indeed with some breeding for seed production would likely be a better grain as well.
Mick Fisch wrote:Just for inspiration look at these videos. ....
Rye straw might be even better than wheat straw, simply because it's so much taller. I think you would still need the wheat paste because I don't think rye has enough gluten, I have no certain knowledge about that, just a general impression.
Tom Turner wrote:This flurry of interest is great. I appreciate it. ....
C. Letellier, I very much appreciate critique as a means of refinement. Thank you. But I have to admit a sort of indifference to cohabiting with insects and rodents and the omni-present risk of fire. That sounds bad, but these things have been a part of our homes forever. That's why we have developed fire departments and mouse traps. Straw bale construction is proven, IMO, to be good enough in these areas of concern. I think ventilation and moisture management is a necessity regardless of whether the structure is wheat straw and wheat-paste or wood and fiberglass. I think the valid critique comes in questioning the possible affinity that mold could have for wheat-paste.
I think the point about labor is misguided. The concept is not to hire a contractor to build your house. It is to build your own house with the help of family and friends, and to not sign a 30 year mortgage to buy building materials. That guy in Arizona who builds partly underground houses by burying old tires has strapping young men sledge-hammering soil into these tires. That is brutal work that very few would be capable of. But the wheat harvest is the kind of work that everybody can take part in and historically has.
I want to add this critique of straw-"bale" construction as it exists today. The walls of a house are the least expensive element of a house. The floor/foundation and the roof are the most expensive. The insulating value of the walls is far less important than the insulating value of the roof. We put 3 1/2 inches of insulation in the wall and 10-12 inches in the attic. The ultimate potential of wheat straw as structure, sheathing and insulation all-in-one is not fully realized until we also make the roofs out of it. That is the Holy Grail of wheat-straw construction. If you only find ways of building wheat straw walls, especially in-filled timber-framed, you're not thinking big enough because you still have to go to the HomeDepot to buy the roof.
C. Letellier wrote: Very few people will build their own homes in this day and age.
Mick Fisch wrote: I've been thinking about the your suggestion about wheat straw glued together. A slight modification might include building modules,
Tom Turner wrote:
C. Letellier wrote: Very few people will build their own homes in this day and age.
Perhaps I assume too much, but I do assume that the members of Permies have all made a philisophical/political/spiritual judgment against the way things are done "in this day and age." This forum is a collective effort to find a new way ...or perhaps to resurrect an old way. I hold it as a firm design parameter that the home I design would be capable of being built by anyone without major investment except for what it takes to get a piece of land.
In Boise we don't have the enthusiasm to patronize Owens Corning that there apparently is in your part of the world, but using your 8"/30" insulation spec a modest 1200 square ft home requires 3,750 cubic feet of fiberglass. At current HomeDepot prices that is $5,600. And the vast majority of that money goes towards burning hydrocarbons to melt sand into glass. If that is the way things are done in this day and age then the way things are done in this day and age is unquestionably wrong and we need to change it.
Early on I was convinced on passive geo-thermal combined with passive solar. But I gradually talked myself out of it for a few reasons: Earth is heavy and either requires very hard labor (I know because I hand dug a small swimming pool once) or a very expensive digging machine. There are a lot of forces to deal with and the structure has to be really strong as well as ground-contact-rot-resistant which inevitably leads to concrete, lots of expensive concrete. Ground water management is tricky and can be gotten wrong with devastating effects discovered after the whole artifice is complete. And while the earth offers us that year round 55 degree environment which really minimizes the Delta T (55 to 70) it is also an effective heat sink which makes the most of that 15 degree delta T, especially if it (the earth itself) is being used as the thermal mass for the passive solar.
C. Letellier wrote:
First off I am not saying the modern way is necessarily the best way. But it is a way we can quantify because it has standards written. Where I am is a far harsher climate than Boise. Virtually any year we we see weeks of 20 below on the cold side and weeks of 110 on the hot side during the year. In a bad year we can see a month at a time at 40 and 50 below and a month of 120+ temps on the high side. So yes insulation is important here. There are very few places on earth where the seasonal swing in temperature can often go more than 160 degrees in a single year.
As for value and cost I would argue that good insulation is totally in keeping with permies values and that fiberglass has its place in that mix. You don't like it, cellulose, demin scraps, straw or any number of other materials can serve in its place. The big thing about insulation done properly is it saves energy for the life of the building. Lets take your $5600 dollar example. If you value forward those dollars it would give a total on the order of $10,000 over 20 years. It is a little low but some of the savings come early which will balance that out. Then say you lived in the home for 20 years. The insulation would have to save you $500 per year to pay for itself. Now half of that insulation will save about 2/3 of the total energy because diminishing returns and meets your early numbers. That would mean $250 a year for the final 1/3 of the savings. Can you make that? It is just over $20 a month. The more insulation the more questionable it becomes. The milder the climate the more questionable it comes. Here I don't think there is any question of it paying off. Most modern construction here banks and building codes are requiring a 2x6 wall with foam outside that under the siding giving an 8 inch wall. I am not saying it is right. Just that it is a basis of comparison.
As for how insulation might be in keeping with permies answering the question another way. I am an independent farm equipment mechanic. The shop built in 1983 and added to since is roughly 40 x 100 with 16 foot ceiling in the big room. By the time part of it is 2 stories total square footage will be over 5000 feet. I heat with coal as the primary and in a typical year burn 6 to 10 ton of coal. For comparison purposes I worked on the coal stoker in an older home. Written on the door from of the coal room for that house was fill dates and tonnages. That house was a 2 story home that given its construction methods was likely built in the 30's or 40's Total square footage was probably about 1000 to 1200 square feet. Reading the door frame of the coal room I know they were burning about twice as much coal to heat that house as I was burning to heat my shop which is basically 5 times bigger in square footage. Why can I get away with that with the shop. One word. Insulation. Yes it is expensive to begin with but it has been paying back for 30 years in reduced energy. I will argue that insulation is totally in keeping with permies ideals.
As for earth berm passive solar I agree there is a lot of energy embodied in the construction and it may not be totally in keeping with permies ideals. That said the best proof of concept I can give was the run through the fall and early winter the year before last of this house. With no elderly and no kids around I decided to push it a bit. I ran until just before christmas without lighting the household heater. I had a couple of days that I got up to 48 degrees in the morning for indoor temperature.(most days the sun came out the house warmed up to the mid 60's to mid 70's and most mornings the house was 55 when I got up) Most people in the area had started heating in Sept and many of them trying to save fuel costs were not running much warmer towards the end of that run. We had many days colder than 20 below in that time. Yet I ran with no heat for that whole time period and was staying almost comfortable. There again over the long haul which is most in keeping with the permies ideals? I particpated in building the house in the summer of 1984 so it has been saving energy for over 30 years. That has to have some value too. A well built home should be good for a couple hundred years so where is the value for the environment?
Tom Turner wrote:...
The building should be in service to the man and not the man in service to the building. I wish you and your Dad had back some of your lives that you devoted to your buildings.
Towards this ideal we need to re-engineer the way we build houses and to incorporate new technology. For example LED lighting is far superior, yet Building codes mandate 110V lights in every room and 110V outlets every 6 feet. Building codes and the fallacy of quality and safety are the biggest obstacle to this re-engineering yet the by-far biggest risk of fire comes from burying romex in the walls a mere 2 inches away from unwitting nails and screws. The codes say that I must install a heating system, that a wood-stove doesn't suffice and that I must wrap the house in Tyvek, that tar-paper isn't good enough. Building codes mandate unnecessary expense and indeed does make us all slaves to our buildings- most commonly by the enslavement to the 30 year mortgage. To a large part this is done to empower the building trades and especially I think the building material suppliers (see Tyvek) which seeks to overturn the time-honored tradition of building one's own home. That is my goal- to eliminate HomeDepot (symbolic image of the material suppliers and skilled building trades) ...sorry I got all preachy.
I love the image of your customer's super-size bale wall. Now if we stay with the wall/ceiling insulation ratio, the common 3.5"/12" (3.4-1) or your better 8"/30" (3.7-1) then with 48" walls then they should put 14 ft of straw insulation in the ceiling. I find the image amusing but I'm not ridiculing it. My concept of gluing together scaled down oriented straw St Louis Gateway arches would also have more, or the same, insulation at the bottom than at the top. That would be the formula for Phoenix where heat is not the issue but cooling is.
As you describe the harsh conditions of your area I begin to think that your geo-thermal is probably the best. When everything is so frigid there is only mother Earth to cuddle-up to.
I do like windows and cringe at the millions of "quality" homes which are constructed to-code by building professionals who are entirely indifferent to where the sun is.
Hans Quistorff wrote:
Windows have 2 purposes (1) to see outside [view] (2) bring light into the house so that you do not have to wast a fuel source on light when the sun is shining. (3) Solar gain is not the best use. You may get heat when you don't want it and they loose heat when you do want it.
Flat windows are also a problem fitting into a curved structure. If you are thinking of using the compressive strength of straw and its insulative qualities by building domes or arches, Then I think Solar Light Tubes are the answer to interior illumination. They can be positioned at any angle. They make little interruption of structural integrity. They are the most neutral for heat loss or gain. They are easily sealed against water penetration.
I insisted on a solar tube for an interior bathroom. It has paid for itself by seldom having to turn the light on even on a moon or star lit night it works. The only loss has been when visitors turn on and off all the lights and fan trying to turn it off when they leave the room.
I can envision using one of those inflated dome forms and stacking straw layers and spraying it with a mixture of wheat past and lime until you have a solid structure. A small one would not need a building permit and could prove the concept. Perhaps layers of chicken wire would add tension strength. But one could make alternate layers vertical and horizontal.
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