A catalog of non-toxic building systems.
Tuesday, April 26, 2005Earth Berm Construction - Under-Earth Without Being Underground
Usually employed as a variation of other building methods, earth berming affords the energy efficiency benefits of earthen construction to other types of structural materials and systems. More common in the traditional architecture of regions with extreme winter climates such as Scandinavia or the American plains region, earth berming has become popular with sustainable architecture advocates and owner-builders looking to get the benefits of earthen construction at a lower labor overhead.
Earth berming quite simply involves the piling up of earth on the sides and sometimes the roof of a structure to provide a thick surrounding thermal mass. This may be done by hand or by mechanized earth moving equipment. This is often enhanced further by a sod covering which protects the berm from erosion and makes it look more attractive. Berms may also be terraced and used as gardening space.
The structure enclosed can be of most any type but its exterior walls require some kind of water-proof covering and buried plastic membranes or pipe channels may also included in the berm itself to act as a means of diverting moisture away from the structure. Exterior insulation in the form of foam materials may also be added, as is common in underground home construction. Sometimes the enclosed structure may be built partially below grade, the excavated earth used in the construction of the berm. Windows tend to be few and small except on one exposed -usually south-facing- side exploiting passive solar heating. Some designs use an earth covered roof rather than a side berm, allowing for more windows and exits but requiring a structure of much greater load-bearing strength. Rustic post & beam, stacked log, stacked stone, steel arch, and ferro-cement shells are common with earth bermed structures today. In the past a great diversity of structures were earth bermed. The vikings would winter-over their long-boats by over-turning them and earth berming them to create a simple long-house, the approach later mimicked in permanent long-house designs.
For non-toxic housing earth berming affords no particular health benefit but does allow for greatly improved energy efficiency and thermal performance for other rather simple, cheap, and quickly built structures, particularly steel or ferro-cement shell structures. Thus one can gain some of the benefits of earthen construction without the massive labor overhead and high cost.
Wattle & Daub - East Meets West
Imagine any stereotypical 'traditional' street scene in Europe and what will likely come to mind is those curious closely-packed town-houses with exposed post & beam structure and a white-washed or buff-brown facade, sometimes criss-crossed by diagonal wooden beams. Though often faked for appearance, this is the hallmark of the traditional European building method known as wattle & daub. Thought to originate in the Neolithic period, wattle & daub was ubiquitous in Europe from Medieval times onward, declining in popularity with the growth in the use of fired brick. But the technique is not exclusive to Europe and has a direct independently invented counterpart in Asia which in Japan is known as komai-kabe. (literally, wall with small bamboo laces) Wattle & daub also later evolved into the traditional plaster-on-lathe interior wall finishing that was ubiquitous in all western countries until its eventual replacement by drywall panel.
Wattle & daub is essentially an in-fill wall construction technique used to compliment a post & beam structure. A grid of thin wood strips -called wattles- is placed in the spaces between main structural members and then covered in a thick plaster-like mixture -daub- of lyme, clay, and straw (and in earlier periods mud or dung as well) which may then be optionally whitewashed for a bright finish and to protect against rain. Komai-kabe is similar, using a woven bamboo lattice between structural members which is covered with a mixture of clay and plant fiber and smoothed to a very fine finish and sometimes covered with lyme white-wash, paper, or other materials glued on (traditionally) with a seaweed derived glue. Komai-kabe is typically much thinner than wattle & daub and has less insulation value as a result but greater breathability. A modern variation of this technique popular with sustainable bulding advocates in France uses the hemp chard based geopolymer material isochanvre instead of the traditional daub material, affording greater resilience, the ability to mold=in relief decorations, and a warmer feel.
Not actually a complete building method by itself but rather an adjunct to post & beam construction, wattle & daub is a very effective means of enclosing these structures and offers many baubiological benefits but is dependent upon a certain degree of skill for which most contractors have no experience. The very high breathability allows for a healthy indoor environment and lets the walls themselves provide some function as a kind of air filter for volatile organic chemicals. This also makes it well suited to more humid climates, allowing free transfer of humidity rather than trapping it indoors -a key reason for its use in parts of Japan. But it is not well insulated and is less suited to colder climates.
As a non-toxic building method wattle & daub is a very good wall system for use with post & beam structures, though, of course, the ultimate healthiness of the home will depend on the use of chemical-free lumber in that primary structure. It has been specified for use in the non-toxic 'EcoNest' homes designed by new mexico based non-toxic housing specialist Paul Baker Laporte. But very few people have skill with this technique and so finding contractors who can work with it may be quite difficult.
Cast Earth - Sustainable Concrete
Cast earth construction is a fairly recent innovation subject to a number of patents that limit its use and the distribution of knowledge about it. It has long been desired to produce earthen construction with the kind of ease found with slip-formed concrete construction where large structures can be fashioned with little human labor and very little time simply by pouring a plastic material into a large form structure and letting it harden into a strong tough material. But for a long time experiments in making a kind of fluid earth mixture capable of this have had mixed results. Natural earth is itself a mixture that lacks a consistency of composition so devising some other admixture to it which can produce consistent results is rather tricky. Still, in the past few years a handful of inventors have claimed to have accomplished this and now offer home construction services based on it.
Cast earth construction is essentially identical to that of slip-formed reinforced concrete construction, using a system of modular or custom made forms made from steel or wood which are assembled atop a -usually- concrete or cast earth foundation and filled all at once with the fluid earth mixture then removed after the material has sufficuently set. The material can be left as-is or finished in a variety of plaster/stucco/tile/or gravel coatings. its appearance is quite similar to rammed earth and sometimes there is a deliberate use of dyes or variable color tone earth mixes to create the kind of striated sandstone-like appearance so desirable with rammed earth. Roofing and flooring can be the same as with any other earthen construction or as with any slip-formed concrete construction. Design variation is limitless as with concrete construction, albeit with an adaptation to the lower compressive strength of the cast earth material and the need for thicker walls. Labor overhead is quite low but the exclusive nature of the contracting reduces any potential savings this might afford.
As a non-toxic building method, cast earth is potentially very good. But there is a problem with the lack of disclosure by inventors of cast earth mixes as to their actual composition. If they are based on all natural inorganic materials, that's probably fine. One well known mix is based on calcified gypsum which would be quite safe. But they could also be based on the use of epoxies or other polymers and there is no way of knowing ahead of time unless the contractors will divulge their trade secrets. Some are open, some aren't. For this reason it may be inadvisable to use this material even though it could very well be completely non-toxic. Unless the contractors are willing to detail their formulas, there's just no way of knowing and it's too critical to take chances on. Hopefully these companies will realize the folly of their secrets as people start to realize they need full disclosure for health assurance -especially with things as important as a home.
For more info see; The Cast Earth Home Page
The Earthship - Sailing Through Time On A Raft Made Of Tires
The brainchild of architect Michael Reynolds and currently developed and advocated by the Earthship Biotecture group in Taos New Mexico, the Earthship is not just a building method but a sophisticated system of sustainable architecture that has set the contemporary standard for housing sustainability worldwide.
The Earthship is based on a variation of rammed earth construction which employed recycled truck tires to contain the earth rather than a large form. The individual tires are then stacked up like bricks atop a rammed earth footing to form walls and are covered with an in-fill of recycled aluminum cans and then covered in a thick adobe plaster. A roofing system of engineered beams or more natural rustic lumber or peeled logs and anchored to steel rebar posts hammered into the tires is then put on top and finished as a compound roof with playwood or plank sub-roof and a waterproof membrane. Flooring is akin to most other earthen construction with poured adobe, stone, tile, or concrete all usable.
This construction method by itself could be employed for a variety of building styles akin to those where adobe is employed and can accommodate many different roofing systems. But the Earthship system employs a very specific type of building design tailored to its sustinability regime. With the standard design a linear series of 'U' shaped chambers are arrayed in a sloping hillside or against an earth berm. At the front, a common corridor links all the chambers and is flanked by a slanted window-wall angled for best solar exposure. Along this window-wall is located garden channels for hydroponic gardening which are fed by greywater from sinks in the home. A similar system may be used in an outside garden channel for blackwater recycling as well. Cisterns are also built into the wall structure, using a catchment system from the sloped 'lean-to' type roof to collect rainwater. A combination of passive and active solar heating as well as some photovoltaic panels are used to provide heat and energy for the home and to provide heat to accelerate decomposition in the sceptic tank. Altogether, these systems are designed to afford the Earthship almost complete self-sufficiency. Year-round energy from the sun, water from rain or snow, and food from the indoor garden fed by graywater.
As a non-toxic housing system, the Earthship has possibilities but one critical issue. Normally, anything made out of old tires is going to be intolerable to the MCS patient. However, the people at Earthship Biotecture claim that outgassing from these tires is completely stopped and/or filtered by the adobe covering and earth fill which block out any heat or UV light exposure of the tire material. Thus they claim no infiltration of contaminants from these into the home environment. But, frankly, they've never done any scientific analysis of this and so their claim is speculation. It is likely correct but since the only way for the individual to know is to personally test it (and not all existing Earthship interiors will be finished to non-toxic standards) it may present a complication for EIs interested in this type of housing. And, in any case, it is unlikely most EIs will be able to handle these tires themselves during construction which makes the owner-builder option very difficult.
Also, like other earthen construction methods, labor overhead is still very high. Though much simpler than conventional rammed earth construction, the large size and weight of the individual earth filled tires makes them difficult for the lone individual to handle. And there are no contractors readily available for Earthship construction so one is left with only an owner-build option. If an EI cannot build this himself nor hire someone else to do it it makes things rather difficult. Still, the Earthship concept is a powerful and practical one and there is no denying its economy in energy.
For more info see; Earthship Biotecture
Rammed Earth - How To Live In Your Old Stomping Ground
Lesser known that other earthen construction methods and seen primarily in France, China, and more northerly parts of Asia such as Tibet, rammed earth construction nonetheless has an ancient lineage and has recently seen revival among contemporary designers for its unique aesthetics. it is also commonly used in combination with many other earthen building techniques where it serves as an alternative to concrete for foundations and footings.
Rammed earth construction is based on the simple compression of earth inside heavy wood or steel forms by foot stomping and heavy tamping tools as well as by mechanized devices. Building up in layers from a rammed earth or sometimes stacked stone footing, the formwork raised whole for each course of added earth. Cement stabilizer is sometimes added to the earth as with compressed earth block. Roofing systems are generally the same as with adobe construction though in Asia a form of earthen compound roofing is traditional, though its performance is poor without frequent maintenence.
Rammed earth construction has produced some of the largest and most massively walled earthen structures known, simply because the formwork must be pretty wide to accommodate many people standing inside it and stamping the earth down with foot and tools. It is also the single most labor intensive of all earthen construction methods. Thus it has more often been used for large community structures, such as the great monasteries of Tibet. However, in the US it has seen a revival among contemporary architects using it primarily for housing. Their attraction? The unique appearance of the finished wall when a mixture of earths in different color tones is used. The striated appearance is akin to that of colorful sandstone and is so attractive the walls are commonly left unfinished with any other material save -sometimes- a protective transparent wax. The use of massive simple rectilinear shapes also ledns itself to many Modernist designs and the heaviness of the walls affords the ability to support very large roofing beams or trusses to allow the use of large open-plan interiors without sacrificing the virtues of thermal mass associated with earthen materials. However, the very high labor overhead for this method of construction -even with the benefit of mechanized compression tools- has limited its use in the US to homes for the very wealthy.
As a non-toxic building method, rammed earth is quite good and offers all the virtues of other earthen building methods. But its extremely high construction cost makes it largely inaccessible to all but the most well-off of MCS patients -which are a rather tiny minority. However, this technique is well suited to large group effort and could do well for co-housing situations where residents are contributing to communal building efforts.
SuperAdobe - Earthen Housing for Earth and Beyond
California Architect Nader Khalili is a person who looks to the past to see novel solutions for the future. Middle-East born and schooled in architecture in Iran and Turkey as well as the US, Khalili has a strong understanding of the Middle-Eastern traditions of earthen construction and saw in them a novel solution to housing problems both on Earth and on the new frontiers in space. A prime example of this is the technology of SuperAdobe, invented by Khalili and developed by his organization The Cal-Earth Institute.
SuperAdobe is a type of 'earth bag' construction that uses continuous tubing as used for sandbags and agricultural packaging. This tubing is filled with a mostly dry mixture of earth and cement stabilizer and coiled up on a cement-filled coil, rammed earth footing, or concrete slab in the manner of coiled pottery to form structures with arches, vaults, and domes. The coils are filled with earth and laid out in a continuous process. Conventional barbed wire is placed between each course of tubing to help keep it from slipping. Window and door frames are formed by wrapping the coils around wooden frame forms which are later removed for window and door fitting. Once the coiled-up forms of the structure are complete it is covered with a thick adobe plaster covering which protect the material from the tubing from deterioration by UV exposure.
SuperAdobe structures can employ much the same variations in form and design as cob construction -sans the finer sculptural details. Rectilinear forms hosting roofing like adobe housing are possible but require the construction of regular spaced buttress features to reinforce the less stable straight walls. But it is generally limited to the use of vaulted and domed shapes with round or arch-topped windows and doors and single-storey heights which are the easiest to build with the technique. These often feature a slightly below-grade floor, the earth excavated being used to fill the tubing of the structure while the surrounding earth affords a little additional thermal mass. Because roof and wall are continuous with these vaulted and domed shapes, the use of SuperAdobe has tended to be limited to the drier climates in order that rainy weather not wear on the adobe-plastered surfaces. But the use of elastomeric coatings or hydrostatic plasters may afford a wider range of climates.
Khalili and Cal-Earth have also devised solar apse structures where a large slanted oval skylight it fixed at the top of a more cylindrical room form to serve for passive solar heating. More classical style apse structures are also possible.
Developed originally as a means to quick and cheap emergency housing for natural disaster victims and as low-cost housing for the homeless, NASA became interested in the technique as a means to constructing shelters for early Lunar and Mars outposts using the materials at-hand at a landing site. In the space version of this technique, the tubing is replaced with a more sophisticated velcro-strip covered tubing that is filled with regolith to form a shape which is then used as a radiation and meteor shield for an inflatable modular habitat installed within it. Khalili has also proposed the use of another Middle-Eastern inspired earthen construction technique for more permanent space habitats. Using a variation of the Geltaftan technique where and adobe building is fired inside to form a hard ceramic structure, Khalili proposes using solar thermal energy to heat a regolith structure to near melting point fusing the regolith into a hard ceramic material that may be pressurized as-is, without any additional internal lining.
As a non-toxic housing technique, SuperAdobe is promising. It is the single lowest labor/lowest skill earthen construction method that exists, going far to ameliorate one of the primary drawbacks common to all earthen building methods. But since no contractors exist to build with this material one is still limited to an owner-build situation and permits may be difficult to obtain even in areas where adobe construction is common. Also, while the stabilized earth material is itself readily non-toxic, some MCS patients may have difficulty with the nylon, polypropylene, and polyethylene sand bag tubing used to contain it. Similarly, those with EMF sensitivities may not tolerate the coils of barbed wire that are included with this. But since the tubing must be adobe covered anyway to elliminate UV deterioation, outgassing from these plastic materials is going to be low to nil. If necessary, natural fiber fabric tubing may be substituted, though it is harder to find, typically has less strength, and is more prone to deteriorate when exposed to moisture.
For more info see; The Cal-Earth Institute.
Compressed Earth Block - The Contemporary Adobe
Cinva ram
Post WWII the countries of the industrialized west began to pursue a variety of international aid programs in the hopes of raising poorer countries to a contemporary standard if living. As well intentioned as this was, it often resulted in great cultural upheaval or was exploited by unscrupulous business interested to create markets -though imposed dependencies- for western industrial goods. A case in point was the well intentioned but ill-conceived attempt by foreign aid workers to impose the use of concrete construction on the Third World as an improvement over the traditional -often eathern materials based- construction methods which these well-meaning outsiders considered primitive and 'sub-standard.' The result was a great loss of knowledge about earthen construction and an imposed dependency on a less sustainable material which in most cases these poorer countries lacked facilities to produce.
Coming to realize this problem, in 1952 more thoughtful aid workers in Columbia invented a simple human-powered mechanical device which came to be known as the Cinva Ram which improved upon the traditional adobe block my forming such blocks from dry or moist earth, with a small amount of added cement stablizer, under great mechanical compression, creating a block of much greater density, uniformity, and compressive strength. This allowed traditional methods of construction to be reintroduced or allowed to carry on while providing greater safety through greater strength of structures and a savings in the consumption of water and the time needed to fabricate blocks. Thus was born the Compressed Earth Block -or CEB- technology which is now found throughout the world.
The basic building methods employed with CEB are generally the same as that of adobe. But the CEB offers many improvements over adobe as a building component and allows for greater flexibility while providing greater performance and a savings in time and labor. The greater physical uniformity of CEBs allows for construction with much less mortar to bind brinks together and in come cases it can be eliminated altogether through precision-formed blocks that interlock rather like Lego bricks. Specialty shape blocks can be created to allow for special structural features or for hybrid construction where reinforced concrete is combined with CEBs to create roof and floor support beams, columns, and the like. This is useful in areas where lumber is scarce or when reliance on lumber is reduced for sustainability reasons. The high density and thus higher compressive strength of CEBs allows for larger structures of many storeys height. It also makes CEBs much more weather and wear resistant so they can often be used without additional protective plaster coatings and can even be left uncovered on interior wall surfaces and still produce an attractive look.
AUM-house with ferro-cement panel roof - Auroville India
The most sophisticated of Cinva Ram product currently available may be the Auram 3000 made by the Aureka company in the Auroville community in India. Using a modular mold system, the Auram produces a great diversity of special function blocks ideally suited to hybrid CEB construction. Auroville's Earth Unit development group has also explored the use of various valt and dome building methods based on CEB and devised a simple but effective prefabricated ferro-cement roofing panel (shown in photo above) which allows for quick roofing construction.
As a non-toxic building method, CEB offers all the virtues of adobe with fewer of its caveats. Labor overhead, time, and maintenance costs are all reduced with CEB and the use of interlcoking bricks reduces the skill levels needed to produce a quality structure. Much taller structures are possible and the hybrid concrete and CEB roofing systems may offer larger spans than single-piece rustic lumber beams can. In general, is one is thinking of building with adobe, CEB is the logical superior alternative. It's only increase in cost is the cost of the block press machine itself, which may be far more than compensated for by the labor saved.
For more info see; The Auroville Earth Unit