Using Natural Materials
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Q: What are the benefits of using natural materials and where does technology fit in?

A: From an ecological standpoint, natural materials have the advantage that they generally don't require much energy to manufacture or even transport them. This savings in energy will likely diminish the amount of greenhouse gas (CO2) that is emitted and also the amount of fossil fuel consumed. From an aesthetic/emotional standpoint, natural materials feel much more, well, natural. Technology is always behind the scenes in our modern world, and I am not one to spurn its use when appropriate. I just feel that one should look to the simpler, natural solutions first, before employing more technological ones.

Q: Would you believe I purchased 2A of secluded Ridge at tax sale, and it was riddled with garbage, cans, 100's of tire, a small stone house w/rotten wood and a dilapidated mobile home. I paid $2K for a crawler loader to remove most junk but all the time I was thinking how could I utilize these items. Kinda wish I would have read about earthships last year. Anyhow my original thoughts were with cordwood but after learning about papercrete, earthships, earthbags, ferro-cement, my mind is open. A rustic theme will prevail around whatever I do but my new challenge will be to build the best I can with the least amount of money. I think I have clay soil there as well as enough, red oak, black locust and cherry that needs to be cut to let the sunshine in and the ridge faces southeast, so I have a lot to dream about. Any reading material you could recommend?

A: It sounds like you have a wonderfully challenging project ahead, with lots of possibilities. I would think of utilizing some of the local resources, like the clay for cob or adobe, or plaster, or floors...and some of the wood for cordwood...the local stones for thermal mass inside...earthbags filled with the soil, ect. I'm really into hybrid building, using what is there in appropriate ways. This is often the least expensive way to go also.

Q: My partner and I are committed to living a life that supports the sustainability of this earth. We are eager to build a natural home. Our dilemma is that we are moving to Alaska in the spring to set-up a new life and have not come across much material that supports this kind of construction for land that far north. Any suggestions, comments or direction to specific resources would be very helpful. Again, your life path is inspiring and highlights our need to integrate this into our life.

A: I would look at any local materials that are in sufficient abundance to consider building with, such as rocks, clay and sand soil, sustainably harvested trees. If there is volcanic pumice-like rock in the region, then you might consider using it in earthbags like I did for my house, as this is insulating...then you can use the rocks and/or adobe soils for thermal mass inside. Another possibility for insulating material to put in earthbags is either perlite or vermiculate, if that happens to be available. I'm guessing that strawbales are not so available that far north, but if they are these could work too.

Q: After seeing a documentary on a German cable on the earthship of Michael Reynolds in New Mexico I was totally amazed. I do not know much about earth building, or how it is accepted and used in the world and I have been asking myself a few questions. I would like to work with the ISF or that would be the IWB (engineers without boundaries) in english I suppose, because I have always wanted to use technology for a good cause. I realize now that it is much easier with earth building to develop help in the places who need it. It is not only an ecological solution but also a social one. What I am asking you is if earth building is diffused around the world in countries who need help for resources such as the ones earth ship can give? I hope you will answer me and maybe give me a few information on earth building around the world.

A: I appreciate your interest in earth building and the Builders without Borders organization. You are right that earth building is especially appropriate for many places where other forms of building would be impossible or too costly. This is especially true of the use of adobe, earthbags, rammed earth, cob, etc. As for the earthship concept that uses lots of used tires and cemented aluminum cans, etc., this may not be as appropriate, because these materials may not be so available. It really depends on what can be found in the area where the house it is to built.

Q: We own 50 acres in southern Belize and we want to start building there in November. I am highly interested in building eco-friendly, self sustainable structures there.The purpose of the land is to be a healing center/community/ tour guide spot for folks to see Belize. For now we want to build a home or two for our personal use. I want to know what is the best materials so use, best design, and cheapest way to do this. There are so many different types of eco-homes, I just don't know which way to turn. Basically we have to drive in any materials that we need which are not locally there, so it needs strategic planning. That is why I am looking for help now.

A: One of the main tenets of sustainable architecture is to use locally available materials as much as possible, so naturally I would ask what materials are usable on this land? Earthbag building can be done almost anywhere, and digging into the ground, especially in a warm climate can help keep the house cool. I am guessing that you are in a tropical forest, so there must be some usable wood available; even if this is not really straight wood, it can still be used for structural supports, decorations, or possibly cordwood walls. Local stones can be used in many ways...there are lots of possibilities.

Q: I am remodeling a 200 year old farm house with environmentally friendly materials- and am a bit stuck on what to do for the exterior. I really would like to try to earth plaster it, but have been strongly "cautioned against" putting that up on a conventionally built home. I have also considered brick and cedar, but would really like something completely natural that I can do myself- any ideas??

A: I presume that your farm house is made of wood, so it depends on how extensive of a remodel you are doing as to what might be appropriate. If you are basically rebuilding some walls from scratch, then you could use quite a variety of materials (straw bales, adobe, stone, cordwood, etc.) but if you need to put something up against the wood, then you need to be careful to arrange things so that the existing wood is not compromised with moisture condensation and such. Conventional stucco treatment over wooden walls includes tar paper as a first layer, then stucco netting (chicken wire) stapled to this to hold the stucco. This same treatment could be used for an earthen plaster, or perhaps stone work. The composition of the wall needs to provide adequate insulation for comfort over the seasons, though, so be sure to allow for this.

Q: I would like to build in Southern Ohio, in a forest, some sun, lots of shade and some damp conditions. What would be some options for building green in these conditions?

A: I would say that you can use most any of the materials and techniques listed at this site, as long as you follow the recommendations for  proper foundations, roofs, etc. I might suggest you particularly examine cordwood construction, since it is fairly easy to do, can utilize some of the wood from your forest, and creates a well-insulated wall that is very easy to maintain.

Q: I have read through all the different materials and construction methods offered on this inclusive website. What methods and materials would you suggests for the Mediterranean environment? Rocks and soil are plentiful. We get a small amount of snow each year and the summers are dry and hot. There is a rainy season and dry season.

A: You will need some insulation in the shell of your home to be comfortable in that climate, and rocks and soil will not provide that. It is possible to make a double wall with stones, so that insulation can be created in the hollow space, but this is a lot of work. Also, earthen materials can be insulated (ideally on the outside) with synthetic insulation, and then plastered. More natural insulation materials that you might find are: strawbales, rice hulls (placed in earthbags), crushed volcanic rock (placed in earthbags). Most likely some sort of hybrid structure utilizing a variety of materials will work best for you.

Q: I'm in Alaska at the present, working and I'm about ready to purchase about 20 acres in NE Washington state. My construction experience is none. I'm hoping to build my own home and I'm trying to find not only the cheapest way but also the easiest non-experience way. I've looked, well just started looking, at ways and I've found that rock seems doable. It's the first time I've found out about papercrete and I'm quite fascinated can you help me get this dream started? Remember I'm looking for the cheapest and easiest way.

A: Building with stones may be cheap, but it certainly is not easy. Using papercrete in your location may not be a very good idea because of the potential for mold. Washington state has lots of trees, so I suggest that you take a good look at cordwood construction, as it is inexpensive, fairly easy to learn to do (there are workshops on this method) and it creates a good insulated wall that requires no further maintenance. You will likely need help with a roof structure and all of the other things that go into building a house.

Q: I am a student whose interest is on natural building techniques, especially Cast Earth. I would be very pleased to know if there's any possibility of assisting me to achieve my aim. My research is on Diffusion of innovative building systems.

A: Of all the building systems outlined at Greenhomebuilding.com, cast earth is one of the most difficult to become involved with; it is proprietary in the US and requires training with a crew and heavy equipment. Many of the other earthen techniques, such as adobe, cob, rammed earth,  and earthbags are much simpler and more direct to employ.

Q: Where can I find information about a good housing system for poorer families in Belize (Central America)? Most of the houses around here are concrete with metal roofs. An ideal house would be termite-proof, cool on hot days, and good under hurricane winds. Resources here include bamboo, lots of tropical woods (mahogany), white lime, and earth.

A: I am partial to the use of earthbags in situations like you describe. I have published a description of how to build a small earthbag domed building at greenhomebuilding.com/riceland . These are termite and hurricane proof, and can be bermed with earth to make them generally cooler. Depending on what you fill the bags with, they can be either insulative or be thermal mass. Even filled with the local soil, the walls are thick enough to provide quite a bit of protection from the heat. Lime can be used for a fairly durable plaster over the bags. Your local woods or bamboo can be used to frame windows, doors, make lofts, shelves, etc. Most of the work of construction is not very skilled.

Q: Do you have any hints or suggestions regarding log homes, either faux logs or something similar. We are preparing to build a home in the Wet Mountain Valley of South Central Colorado about 10 miles north of Westcliffe - on the east side of the valley looking at the Sangre de Cristo Mountains (home elevation ~8100 feet). My wife has her heart set on a log home but I'm pushing back and am seeking an alternative (less to maintain, better insulating properties, more environmentally friendly, ...etc.)

A: I lived for many years just over the mountains from you in Crestone, so I know how extreme the climate can be there. Given this fact, I would highly recommend that you opt for the best insulation you can muster, and that typically is not logs. My other objection to log homes, is that in general they use a lot of a dwindling resource, the extraction of which is undermining ecological health in forest environments. I would suggest that if you want the log home look, to just use the rounded slabs on the outside as a siding to a very well-insulated framed wall. I also suggest that you employ a passive solar design to help with heating your new home.

C: You recently sent a document for review titled "Development of Straw-Cement Composite Sustainable Building Material for Low-Cost Housing in Egypt". I did read the manuscript and can offer you some of my observations. First of all, I applaud anyone who is seeking sustainable solutions for building technologies, as these are essential for our continuing health and success as a species. The aspects of the concept presented for manufacturing building blocks from rice straw and cement that I would consider sustainable are:

• One component (the straw) is a surplus renewable material that when utilized will take it out of the waste stream and avoid possible air pollution from burning it.
• The straw is free, which lowers the cost of the production
• The straw-cement blocks can be produced locally by relatively unskilled labor, again lowering costs
• The resultant blocks provide better insulation values than conventional concrete blocks.

Q: I would like to build a natural, environmentally-friendly and beautiful home. How should I go about choosing what to build with? When should I go with cob/adobe/strawbale/earthbags/rammed earth/papercrete?

A: There are several criteria that can help you make these choices. The first thing to focus on is actually not the material, but the design and function and  that will be guiding you. Once you know what and where you want to build then you can look at how and with what materials.  Often people will say that they want to build a cob house, for instance, when in fact cob would not be a wise choice for a house in their particular climate.

Generally, in any climate where one must endure extremes of temperature, the outer shell of a home should be constructed with materials that provide good insulation. These materials are usually fairly lightweight, such as strawbale, earthbags filled with volcanic rock, or papercrete. Other denser materials can provide insulation if they are used in such a way to create a void in the wall that can be filled with insulation.

Another principle is to place plenty of thermal mass materials on the inside of the house. These are the denser, heavier things, such as adobe, stone, brick, tile. Thermal mass materials will tend to stabilize the interior temperature of the house, keeping it comfortable most of the time.

So you can see that what I am advocating is quite possibly using a variety of materials to build with in a hybrid fashion.

Other criteria for making materials choices that are sustainable have to do with the "embodied energy" that any given material represents. This means the amount of energy that has gone into its procurement, manufacture, and transportation to the building site. You want this to be as low as possible because, typically, energy consumption these days means air pollution and fossil fuel depletion. For this reason it is best to use local, natural materials for the most part.

Fortunately, natural, non-industrial materials also tend to be healthy and non-toxic...which is another sustainable criteria. Building to last is a final consideration. Use durable materials in such a way that the building will be there without lots of maintenance for centuries.

Q: What key strengths and weaknesses (or limitations) of each of these materials do I need to know about?

A: Cob, adobe, and rammed earth are all basically the same material: soil that is composed of roughly 70% sand and 30% clay. Cob has some added straw that gives it some extra strength and insulation, but not much. These earthen materials are generally best used as thermal mass, and so should be insulated from the external atmosphere. They tend to be extremely durable and will last for centuries.

Strawbales and papercrete provide very good insulation indeed, but must be protected against deterioration from moisture.

Earthbags have the unique capability to be either thermal mass or insulation, depending on what they are filled with. As insulation they can be filled with crushed volcanic rock, rice hulls, perlite or vermiculate. As thermal mass they can be filled with practically any native soil.

Cordwood uses short pieces of scrap wood in a matrix of mortar, with a hollow space on the inside, and this way they represent a natural building technique that provides both insulation and thermal mass.

Natural stones provide excellent thermal mass and durability.

Q: We are getting ready to build on an ocean front lot on the Big Island HI. What to use? I want to build green and have concerns about the ocean and salt corrosive qualities, and mildew is a problem here. Any suggestions?

A: In Hawaii you are blessed with a lot of volcanic stone, so I would consider working with this material for your home. It is very corrosion and mildew resistant. You can use it to fill earthbags like I did with my house (see This page ) or another possibility is a sort of pumicecrete like shown at here...or you can just build with the larger stones as with ordinary stone masonry.

Q: My son and I would like an eco friendly home and are not sure which way to go. My son is going for a degree in recording, and eventually would like to establish a recording studio, as eco-friendly as possible within this home. We are wondering what the possibilities of this are and which medium might be the best to go with.

A: Sound recording studios require quiet, well-insulated rooms with good acoustics. There are many materials that can provide this, but one obvious choice is strawbale construction, since it is also ecological. Another possibility is earthbag construction, but this is not as common. Actually any well-insulated or thick-walled house might serve your purpose.

Q: I am a sculptor and I have always had a disdain for square or rectangular rooms, spaces, etc. It never felt right and it still doesn't. It feels like a box and if you viewed my neighborhood from a plane, you'd see a whole bunch of boxes, each with people believing they live according to their own design. It all feels so inauthentic somehow.

Anyway, I have wanted to build an adobe or cob style home for a long time but I live in Canada, currently in the Toronto burbs but soon to be north/west of Edmonton. The first thing that I picked up from your site is that cob homes are not suitable for cold weather (I think you said "extreme" which is probably what I'll be getting out there. It can get pretty darn cold in that area, like -40C.

How can I build an insulated home in those conditions and have it be like an adobe or cob home? Maybe it would have to be straw bail? Something else?

A: I agree with you about how much people take for granted that rectilinear dwelling space is natural, which of course it isn't...and how wonderful it feels to spend time in more curving spaces.

And you are right about cob not being the best choice for a climate like yours. But that doesn't mean that you can't enjoy living in a natural, sustainable and rounded home.

Strawbale homes are great for insulation and for naturalness, but the bales themselves are rectilinear and therefore do not lend themselves to imaginatively curvy spaces, although it is possible to force them into somewhat curved shapes.

A better choice might be either earthbag or cordwood construction...especially earthbags, since you might be building partially underground, but a hybrid of the two might be nice too. If the earthbags are filled with an insulating material, such as crushed volcanic rock (as I did with my home) or perhaps perlite or vermiculite, then it should be quite comfortable.

Q: The most compelling homes I have seen are the earth homes.  They have organic shapes, no straight lines, and they feel cozy and warm. They also have that Santa Fe clay stucco look that I love.  I wanted to build quite a large home and I'm not sure how big you can go with earth bags.  Maybe it would have to be multiple "mounds" connected together, rather than more stories/floors, as in a geodesic type of dome.  This would probably be better for heating and cooling.  I have been  trying to figure out how I would do that with a large open space concept dome with 3 floors (ground, second, and third). 

A: Earthbags are very malleable in terms of shapes they can form, so spaces can be large or small, curved or straight...whatever you want. Very large domes (over 20' in diameter) can be difficult to engineer, but they can be connected together as you suggest. Domes with lofts are easy to create, but three stories would be difficult. Natural earthen plasters can be put over both straw and earthbags as a final finish.

Q: I'm concerned about straw because of what might be living in there that could get trapped inside and die, like mice or rats.  I guess I should be concerned about bugs in the dirt too in regards to earth bags.  How does one effectively avoid killing anything?

A: While it is true that rodents can burrow into straw, I think it is rare that any actually get stuck in a wall and die there. Once the walls are carefully plastered it is difficult for anything to get into the straw. Also, compacted soil or crushed rock is not a pleasant habitat for insects or animals, so that is unlikely.

Q: Do you know any insulation ratings on earth (rock) bags and straw?  Maybe I would have to do a double thick outer wall?

A: The R-value of straw depends to some extent on the size and compactness of the bales, but most are probably around R-30 or R-40. While I am not aware of any scientific ratings for scoria (volcanic stone), my empirical experience would place them in the same category as straw, or about R-2/inch. This is pretty good, considering that many houses considered well-insulated only have walls of R-20, say.

Q: I'd love to see some alternative style homes but I don't think that there are any around here.  Oh, what about building permits and restrictions?  I'm wondering if I will even be "allowed" to create my organic home.

A: I'm sure there are plenty of alternative homes in Canada, but finding them might be difficult. You might try asking local builders or realtors if they know of any. Most building authorities do allow some alternatives to conventional building, but it often is necessary to prove to them that the building will be sound; this may mean having an engineer review and stamp the plans.

Q: Last question... the stucco layer, is it mud?  How does it fair to snow and rain?  How much maintenance?  Should I have something more durable for our climate?  I want something that not only can stand the test of time, but can stand the test of the likely upcoming earth changes.

A: Earthen plasters can be stabilized to some extent with the addition of a small amount of Portland cement or other additives. Lime plasters are more durable and yet still breath to allow transpiration through the wall (essential for straw). Cement stucco is the most durable, but does not breath well, nor does it have that natural feeling. Houses with substantial eaves will protect the plasters much better than would exposed domes.

Q: My children's charter school Building Committee is looking to design and build a new school. The process has just started with the conceptual phase. We have hopes of construction being completed in about 6 years. I want to make the case for alternatives to concrete and steel. Since it's a Montessori school with a strong inclination towards green strategies, I want us to consider what is feasible for our part of the country.

We're in Raleigh, NC. Which of the green building materials would work best for this low-rise construction? The school will be of several smaller buildings--all single floor. The total square footage for the approx. 500 students is expected to be 85,000 sq. ft. Of course, codes are a concern so nothing too drastic, but which of these materials are feasible and suitable for our southeast climate? Can you guide me to the correct resource?

A: There are a variety of green building materials that should do fine in your area, including, strawbale, earthbags, cordwood, adobe, cob, stone...but the more important question is the overall basic design of the building. Once you have decided on the function and layout, then you can address how best to accomplish this, based on local availability, greenness and appropriateness of the possible materials. Often a hybrid approach is the best solution.

Addressing local code requirements is another consideration, and for this it is sometime necessary to get a local architect or engineer to stamp the plans, or at least get the approval of the local authorities.