Settlers moving into SEE initially will have their choice of housing, subject to their ability to pay for it. We have hoped that housing could be kept low-cost so that people would be able to save easily for investment in businesses that would further the Millennial Project. The current thought is that community capital might be $8,000 per adult and that a single adult might expect to put up to $12,000 into housing.

Three housing designs that meet or beat the $12,000 goal have been identified. They are the Comfortable House, the Healthy House, and the Organic Growth House.

The Comfortable House is a mobile home. The Healthy House is a site-built house that calls for spending more at critical points in order to maximize the indoor-air quality. The Organic Growth House has a very solid post-and-beam framework, a roof, trailers for immediate habitation, and little else immediately. It is designed to be filled in and extended both horizontally and vertically.

We do not want an appearance of a mobile-home park or a suburban neighborhood. One alternative we envision is very tight clusters of four houses plus a cluster center building. By "very tight" we mean somewhat less than two meter walkways between the houses. These clusters would occupy one quarter of the land leaving three quarters as green space. Each house would have a clear view from two sides. This would allow single-story housing densities of 10 people/acre (40 people per acre in the clusters) so a 10-acre lot would support about 100 people.

As low-cost housing is a central idea in SEE, considerable discussion and thought has gone into what housing we might use. This section has reviews and comparisons of several books on housing, focusing on health, cost, and durability.

Simply Build Green: A Technical Guide to the Ecological Houses at the Findhorn Foundation, by John Talbott. Copyright 1993. ISBN 1-899171-90-8. Published by Findhorn Press: 220 pp.

This book is well titled, but it might also be titled, "The Green is in the Details," which is the recurrent theme in the book. Three main classes of details recur: selection of a supplier, building design, and materials selection. The subtitle of this book tells you that is based on the experience at Findhorn. This means that one thing not covered is how to keep a house cool in a hot climate.

The bulk of the houses considered are regular rectangular styles that would be difficult to tell from most houses you see. The difference lies under the surface in the details-or are actually invisible, in where some of the materials came from. The houses are one-and-one-half or two-story buildings.

The book consists of five sections plus appendices. The first section is an introduction to Findhorn and to German work under the name of Baubiologie (building biology). The second section considers types of construction for parts of a house, such as foundations, floors, walls, and roofs. The third section goes into detail on types of materials such as wood, stone, clay, insulation, plaster, copper, and paints. The fourth section is devoted to various aspects of energy such as insulation, active and passive solar energy, glazing, heating systems, lighting, and renewable energy sources for home use. The fifth section is a miscellany including water conservation and treatment, electrical systems, and shared facilities. The appendices include tables of Baubiologie ratings, energy requirements to produce various materials, a tabular comparison of various insulation materials, references, and a brief list of other ecovillages.

Baubiologie is the study of how buildings affect the health of their inhabitants. This study started in Germany but has spread to the rest of Europe and to the U.S. Their comment on a major work from this study, the Working Papers in Building Biology from the Institute for Building Biology, is that it is a good reference work but lacks details for putting the concepts into practice in actually building a house. Their book clearly intends to fill such a role. The book also aims to incorporate not just health effects on the inhabitants but the effect of the construction on the environment.

The second section begins the detailed discussions. After carefully selecting deep piers as the most suitable of foundation methods, they found that Scottish building regulations made it irrelevant since the whole dirt surface had to be covered anyhow. Their constrained choice was for strip foundations. This is the most common foundation for residential buildings. It consists of strips of concrete which are deep enough to reach below the frost line, and which directly support the building's walls. U.S. code for site built housing specifies strip foundations or a heated concrete pad. For manufactured housing, I-beams are built in and piers are often specified for their support.

The floors are considered as ground floors or internal floors. Ground floors could be concrete slabs, but they preferred a crawl space plus a well-insulated floor for the ground floor to control radon exposure. In selecting an interior floor, they gave additional thought to sound insulation, pointing out its importance if a house is shared by unrelated individuals. It is rather difficult to get good sound insulation in a floor because the sound is transmitted through the floor joists and broadcast by the ceiling which must be firmly attached. They found the best sound insulation resulted from a "floating floor" consisting of layers of 19 mm plywood [the only use of plywood in any of the houses, they caution], a 25 mm coconut mat, a 19 mm floor specialized plasterboard with taped joints, and finally a 27 mm tongue-and-groove softwood floor surface. The key point was that the tongue-and-groove floor was not nailed but floated on the various substrates.

The section on wall construction is a quite complete example of the typical section: here are standard techniques; this is what we thought about; this is what we did; we cannot tell if it was effective. The standard techniques discussed for walls are solid masonry, masonry cavity, masonry clad timber, stud walls, and post-and-beam walls. In the U.S. stud walls are the overwhelming majority. They chose wood-clad stud walls in order to use renewable resources for as much of the construction as possible and because wood requires the least experience to deal with. The thinking went into what covered the studs. They review that before about 1920, materials such as brick, gypsum plaster, clay, and timber which breathe well were in common use, but that they were used in such a way that two or three air changes per hour was common when there was no wind. This avoided build up of moisture or noxious chemicals but was quite inefficient for heating. Recent practice has gone to the other extreme, sealing the house tightly to get heating efficiency but getting poor indoor-air quality.

The walls they use are a careful return to breathing walls while maintaining good insulation. The principle consideration is to avoid build-up of water inside the walls as moist warm air moves out through the walls to the cold dry exterior. The basic way to do this is to have less permeable surfaces on the inside and more permeable surfaces on the outside. In standard current practice, "less permeable" is implemented as "almost impermeable" with a layer of aluminum foil or polyethylene sheeting. What they have used is a low-permeability layer just outside the plasterboard interior walls, insulation (discussed separately), a high-permeability fiber board, and wood cladding. The key is the ratio of 1:5 in the permeabilities of the two layers controlling vapor flow. This ratio meets their building code for vapor control [and building codes are notoriously conservative], while still allowing vapor-laden air to move out through the walls. The result, as measured in air changes per hour, was unknown as of the writing despite some attempts to measure it. It has been observed that water has not built up in the walls.

Roofs were implemented as walls with a different outer layer. After considering slate, concrete tiles, cedar shakes, and asphalt shingles, they chose to use clay tiles for the roof surface. This is an interesting example of their attention to the detail of supplier. They interviewed many suppliers in Britain and did not find any that were restoring the environment after digging up the clay. They wound up buying from a French supplier. Here's another interesting point: they found from experience that it took much less time to design all roof dimensions including building length, roof overhang, skylights, and dormers as even multiples of the tile size rather than cut the tiles to fit an arbitrary length. Cutting tiles is very messy and time consuming.

Considerable experimentation went into the structural system in order to be able to fully use the area in the second floor. The simplest thing is to have roof rafters meet the tops of the walls, but this results in much of the second floor space being unusable-the typical "one-and-one-half-story effect." They worked to add a few feet to the height of the walls so that they could have a full two story house functionally while not wasting the space contained within the roof. The problem is that the walls are not built to take the outward thrust of the roof. Ceiling joists have the tensile strength to take this load, but if the wall is extended upwards, how to take the roof load becomes a problem. They wound up with a hefty central roof beam supported by columns (concealed in internal walls) which rested on a floor supporting beam which again was supported by columns. Two sod-roofed buildings were built as strictly one-story buildings.

The third section focuses on materials.

Timber is a very important material for small buildings, having good strength in compression, tension, and torsion; being easy to work; and being derived from renewable sources. They review British work on reestablishing forests, and the difference between uncut forests and forests managed for timber and other uses. Almost all timber gets chemical treatments creating some of the most noxious vapors in a house, even though treating for wood not exposed to weather is quite unnecessary. They wanted to avoid this in their timber and found a local mill which could make boards, studs, beams, and various other cuts to their specifications with no chemical treatments. They did find that it paid to have the wood "regularized," which is to put it through a dimensioning machine and to dry it in a kiln. For timber exposed to weather, some form of treatment is advisable to prevent rot. They chose borax for treatment of timber in such uses including sill and cap plates of the stud walls as well as the outside cladding.

In all their considerations of supplier they considered that transportation rests heavily on fossil fuels for which unpriced externalities (carbon dioxide production and fixed nitrogen production) are assumed to result in gross underpricing. There is certainly underpricing, but how much is open to question. [A study by Michael J. Schauer found that when professional economists estimated the parameters of a model of the implicit cost of greenhouse damage, the average price was $8.3/ton of carbon in the atmosphere. When the economists made a direct estimate of the implicit cost, their mean was $112/ton. For gasoline at 1 $/gal, the former amounts to a 3% increase and the latter to a 34% increase.] In any case, a local supplier was preferred, and an appendix indicates that they believe the local supplier for wood resulted in less energy used by a factor of seven for their wood as compared with bringing it in from a distance. As mentioned, they wound up with a French supplier of clay products anyhow. This is the sense in which the green is in the details, and requires careful balancing of commodities which are poorly priced in their reflection of environmental effects.

Stone has many advantages, but one severe disadvantage-considerable skill is needed to work with it. Findhorn used stone where skill level required was not great, such as walkways, patios, and low walls. They found local quarries and bought the irregular remains from squaring stone pieces for market. For a cost of four pounds/ton they got very interesting granite and sandstone pieces.

Insulation examined included natural vegetation sources (cork, straw, woodwool, fiberboards, and cellulose), fossilized vegetation sources (polystyrene and polyurethane), and inorganic minerals (fiberglass, rock wool, perlite, vermiculite, foamed glass, and foamed concrete). They chose to use cellulose. This choice is not quite as insulating as fiberglass but, while fiberglass itself would not be objectionable, the commercial insulation contains many resins and glues to help it maintain its shape. They applied the cellulose either as a wet spray during wall construction or as a dry-blown fill. They examined the resulting insulation a year later by infrared photography and found that the dry-blown fill never had gaps but that where an inexperienced operator had applied wet-blown cellulose there tended to be gaps. Thus, the low-skill way seems to be dry-blown cellulose.

Plywood, chipboard, and plasterboard are examples of sheet materials used copiously in modern construction, making building construction easier and faster. Unfortunately, most of the wood sheet products have hefty (up to ten percent by weight) portions of urea-formaldehyde or phenol-formaldehyde as glue. Furthermore, standard manufacturing uses excess formaldehyde to speed up the curing. The excess formaldehyde eventually outgasses making them a major contributor to indoor air pollution.

They located one "medium" board with no additives; it was made in Sweden. This board is made from wood waste (sawdust, chips, thinnings) mixed with water, heated, and compressed. Under these conditions, the lignin, the natural bonding material in wood, is rebonded to the wood fibers. The board has compressive strength equivalent to plywood but has less tensile and torsional strength. They were advised by their engineer that it could be used in the walls but not in the floors. Thus this material is used as the low-penetrability layer immediately under the inside plasterboard. This medium board also has one other significant disadvantage compared to plywood, that it is easily damaged by water. Thus, it was only suitable in a near-interior use. As noted, a plywood was used in the floors. They note an important detail about plywoods, that phenol-formaldehyde glues outgas less than urea-formaldehyde glues if plywood must be used.

Findhorn also makes considerable use of bitumen-impregnated, low-density fiberboard. It is the low-permeability board used in the outer wall. Bitumen is a compromise necessitated by the need for a water-resistant board in the outer walls. Having it only in the outer wall, however, minimizes its impact on interior air quality.

Plasterboards vary considerably in their toxicity. The gypsum base is non-toxic. However, some gypsums contain radioactive phosphorus. The glues used in the bonding of the paper faces have different toxicities. They have used plasterboard on all the interior walls and also as part of the floating floors.

Copper plays three roles in the Findhorn housing. First, there is little choice in using it for electricity. Second, they usually use it for water pipes although plastic pipes (which are much easier to use) have been utilized for some heating functions. Third, copper is used instead of lead as roof flashing so that the water running off can be collected for use in gardening.

A couple of buildings were made a bit out of the ordinary by having turf roofs. A turf roof needs a low slope, so in two places where a view indicated the use of a low roof anyhow, turf roofs were employed. The process is described in detail.

Modern wall-to-wall carpets usually contain a large number of chemicals, up to thirty, to control everything from mildew to stains. Findhorn has made extensive use of cork for floors in baths, kitchens, and halls. Elsewhere, the predominant choice has been tongue-and-groove softwood. They learned the hard way why it is traditional to leave softwood floors unnailed for a year-wthe wood shrinks. In the areas where floating floors were used for sound-control reasons, there was no difficulty adding another board after a year. Elsewhere, they have cracks in their floors. The softwood floors have also required developing a practice of removing shoes before walking on the floors. They have used hardwood floors in heavy-use buildings, especially community buildings. They have used rugs also. The detail here is the backing. Even with a wool rug, the backing may be plastic or synthetic rubber. Jute is a preferable natural backing. They found an 80%-wool/20%-nylon rug to be an acceptable material, also.

Two flooring materials are planned for use, although they had not been used as of the writing. One is fiber matting of sisal, coir, seagrass, rush, or maize. The latter three require some care in keeping them from drying too much. They are all tough and low in cost as floor coverings go. The other is rather surprising: linoleum. This can be made from totally natural products. Finding a supplier is difficult since vinyl has mostly taken over the linoleum market. They expect to use linoleum where they have used softwood in the past.

Paints are the innermost layer of wall and ceilings, and thus the most critical in terms of air quality. While water-based paints have gained greatly in popularity due to the ease of use, paint particles are not soluble in water so these paints add a detergent to hold the particles in suspension. Since the detergent tends to froth, a defoaming agent is added. Since the defoaming agent slows setting, chemicals to speed up drying are added. The result is a cascade of problems covered up by adding more chemicals. When the Findhorn folk realized this aspect of water-based paints, they stopped using them.

Oil-based paints, whether a natural oil or a petroleum-based oil, dissolve the alkyd paint particles and evaporate to leave the paint particles in place. The synthetic oils also have impurities from their manufacture and tend to include various mildewicides, fungicides, and heavy metals. Findhorn has gone with the natural organic solvents of citrus peel oil, and pine and gum turpentine which have much lower impurity rates (and of course no petrochemical impurities). They also come from sustainable sources. They are less than thrilled with the results, but satisfied. Despite manufacturers' claims, multiple coats were required for coverage. They use three coats for external wood: a primer and one color coat applied before cutting or using the wood and a final color coat after putting it in place. There had not been enough time, as of the writing, to know the lifetime of the paints.

The fourth section of the book deals with energy and has less in it that is not well treated elsewhere. A business based at Findhorn makes solar panels for heating water and they have used these in active solar-heating systems. Double glazing is standard but triple is sometimes used. A preference for natural light to artificial light has led to considerable use of skylights despite the loss in insulation value. Propane is their fuel of choice since natural gas mains have yet to be extended in their direction. Wood fuel is used enough to cause problems of air pollution. Fluorescent light bulbs rather than incandescent are standard. Appliances are compared carefully for energy use and water use.

They have begun to generate electric power using modern wind technology. By reducing their energy needs, they hope to generate 60% of their power from wind and 20% from solar, and to buy the remaining 20%.

The fifth section deals with a miscellany of issues. Water conservation turned up one interesting fact. They had originally planned to keep gray water and black water separate. By installing low water-use toilets, the black water alone was insufficient to move the wastes to treatment facilities. Thus, inside the houses the two outgoing streams are separate but they are combined immediately outside the house.

Radon levels are a serious issue in ground floor areas. Action levels in Britain have recently been reduced from 400 Bq/m³ to 200 Bq/m³. The ASHRAE (American Society of Heating, Refrigeration, and Airconditioning Engineers) has recommended 73 Bq/m³ as an action level for radon. Continuous exposure to even this level, however, would correspond to 100 chest x-rays per year [what vintage x-ray machines was not stated, but may correspond to the copyright date]. Thus they expect continued reduction of what is considered safe.

Concrete slab floors pass radon gas through micro cracks, so they chose to use a crawl space and flooring. Measurements in a building of theirs with a concrete slab floor showed 45 Bq/m³ while measurements in one of the houses with a crawl space gave 12 Bq/m³. They conclude that there is a radon problem for them and that the crawl space is an effective means of control. Radon, being a heavy gas, is most severe in ground floors. Having bedrooms located in upper floors also reduces the problem.

They argue that their buildings are not much more expensive than standard construction. They do not argue that the cost is less. There is a major weakness in their economic arguments which is that materials costs only are compared. This assigns a zero cost to labor which is just as bad a mistake as assigning a zero cost to carbon dioxide production from fossil fuels. It is fairly clear that a much safer living environment is being purchased, but it is not clear what price is being paid.

Also, it seems clear that the environmental impact of the buildings is significantly less than with common construction practices. Some of the costs of the buildings are clearly directly related to this as in buying roof tiles from France instead of locally. But it is not clear what extra cost there may be to the buildings and if there is extra cost, how it should be allocated between the two goods being bought.

The three approaches compared here are those presented by Sydney and Joan Baggs in The Healthy House (HarperCollins, 1996), John Bower in Healthy House Building (Healthy House Institute, 1993), and John Talbot in Simply Build Green (Findhorn Press, 1993). This comparison is limited to considerations affecting the personal health of the inhabitants of a house rather than those affecting the community or even the Earth as a whole. At least one of the authors would argue that any such limitation is impossible since the world must be viewed wholistically.

What Affects Health?

The authors have different health concerns as reflected in the amounts of space the various authors devote to different issues. The order presented here is alphabetical. Thus the Baggses come first, and the discussion is the longest for them not just because they have the longest list of considerations but also because many terms need at least a brief introduction.

Sydney and Joan Baggs:

* Feng Shui. This is a Chinese "blend of geomancy and astrology." It gets two chapters in the book plus several references to the notions outside the chapter.

* Plantings around the house. This gets a long chapter but little outside the chapter. The topics discussed in the chapter range from biological energy fields and the use of feng shui to using permaculture principles for controlling temperature, waste disposal, and noise control.

* Geometric Form. A chapter is devoted to forms such as pyramids, platonic solids, and principles of morphic resonance and bioharmonics. This topic is mentioned little outside the chapter.

* Geomagnetic and electric fields. Concern about electromagnetic fields (EMFs) appears throughout the discussion, from site selection to materials selection.

* Volatile Organic Compounds (VOCs). These are organic compounds which volatalize easily and can reach significant concentrations in the air inside a house. Some of these compounds are carcinogenic, others are poisons, and some are allergens for many people. This topic is discussed in several different contexts.

* Biological contaminants. These can range from mold and other fungi to dust mites. Biological contaminants can directly generate allergic reactions. They can also produce poisons and allergens from otherwise benign materials. Or, as with termites, the actions taken to control them may introduce poisons or allergens into the indoor environment. This topic is discussed in several different contexts.

* Relative Humidity. The reason given for the importance of this topic is its impact on biological contaminants. Comfort is also mentioned.

* Safety, including disasters such as fire and earthquake. There is direct discussion in about twelve pages plus discussion in several different contexts.

* Radon. Radon is a radioactive gas formed from decay of Uranium in earth. Its effect is primarily through the elements into which it decays since they become part of the dust in a house and can then lodge in lungs. These elements in turn are radioactive and promote lung cancer. This topic is discussed directly in a few pages and also in several different contexts.

* Noise. "Noise can cause anxiety and even illness." There is direct discussion in a few pages and also in a several different contexts.

* Combustion products and side effects. Combustion products include partially oxidized hydrocarbons, carbon monoxide, sulfur dioxide, nitrogen oxides, and particulate matter. The consideration is limited to avoidance in site selection.

* Fluorescent lights. Fluorescent lights have too much UV in their spectrum. This topic is given half a page.

John Bower:

Bower is mainly concerned with indoor-air quality, therefore with:

* Volatile Organic Compounds.

* Biological contaminants.

* Directly introduced poisons and carcinogens, such as lead and asbestos.

* Combustion products and their side effects. The primary concern is with combustion products inside the house from burning gas, oil, or wood to heat air or water. Besides the combustion products, leaks of gas and oil are cited as common problems.

* Dust. Dust is a heterogeneous mixture of many particulate and fibrous components. It commonly contains allergens.

* Radon.

* Electromagnetic fields. Bower argues that electromagnetic fields are not important.

* In a very brief passage, Bower mentions fluorescent lighting, temperature, humidity, and noise as other factors in addition to indoor air pollution that may affect the "feeling of well being".

John Talbot:

Talbot's health concerns are so thoroughly mixed with other environmental concerns that it is difficult to separate out the health concerns.

* Volatile Organic Compounds.

* Radon

* Auditory Privacy. This is likely to lead to general abatement of noise levels but the motivation is more the need for noise control inside the house than for control of noise from outside.

* Electromagnetic fields. The Earth's electromagnetic field has its strongest frequencies between 1 and 20 Hz. When astronauts first moved out of this field by leaving Earth, they suffered sleep deprivation. NASA now provides an artificial electromagnetic field at 7.83 Hz which allows the astronauts to sleep.

Support, citation, and indexing.

Support for statements and citations make it easier to check an author's statements. Indexing makes it much easier to locate discussion of some topic. The following are some useful levels for noting the support that an author gives for statements made.

Dogmatic-no support given.
Secondary source-one secondary source cited.
Secondary research-several secondary sources cited.
Primary source-one primary source cited.
Primary research-several primary sources cited.
Personal experience-direct experience of the author.
Personal research-direct experimental results by the author.

The Baggses' support is most often dogmatic. A secondary source and some primary research are also used. When another source is cited, the citations can be found grouped by chapter. The book is indexed.

Bower's support is most often his own experience or dogmatic. He also conducted a few of his own experiments and has some secondary sources. The secondary sources are included in an annotated bibliography. (Annotation of a bibliography greatly increases its value in trying to see where to dig next.) The book is indexed.

Talbot's support is most often dogmatic. He devotes a section of each chapter to his own experience. He cites a few secondary sources which are included in a bibliography. The book is not indexed.

Sydney Baggs, the cover notes say, is an architect who has designed over 400 healthy houses. It is unfortunate that this experience is reflected mainly in a dogmatic form (correspondence with him indicates that he lost editorial control to the publisher). Compare, for example, the Baggses' and Bower's discussions of measuring magnetic fields:

Baggses: "Before purchasing electrical equipment, check it with a portable magnetometer (see Resources List). This is an essential purchase if you are serious about correcting an unhealthy electroclimate. Ideally, when the piece of electrical equipment is connected to the main power supply, the meter should read no more than 100 gamma (100 nanoTeslas [nT] or 1 milliGauss [mG]). Take your measurement from the distance you will be when exposed to the appliance. For example, the magnetometer should be about a centimeter (1/2 inch) away when testing a hairdryer, but about 50 centimeters (20 inches) away when testing a computer monitor" (p. 169).

Bower: "In his book, Cross Currents, Robert O. Becker suggests a policy of prudent avoidance. He recommends avoiding field strengths greater than 1 mG. for continuous exposure. Others have suggested that anything below 3 mG. is probably a relatively safe level. Becker also notes that higher field strength can probably be tolerated for short periods." Bower also reports, "I have taken a gauss meter and measured the field strength in an average residence. In many cases it is difficult to measure any EMFs resulting from the 110-volt electrical wiring that feeds the majority of the circuits in a house. I have measured a field strength of 30 mG. right next to an electric baseboard, but since the field strength diminishes rapidly the further you move away from the source, the reading was only 1 mG. about a foot away from the heater" (p. 244).

Bower has told us where the 1 mG-level can be traced back to, and he relates direct experience that gives some idea of how rapidly the magnetic fields drop with distance.

Talbot does not discuss magnetic field strength but does discuss electric field strength. "The strength of these fields is measured in volt/meter (V/m) and is a function of the power use or current flow and the distance from the source. So things like electric blankets that are immediately next to us tend to have a greater effect than say a light fixture across the room. To give some idea of relative values, an electric blanket field is has a strength of around 250 V/m while a food mixer is about 50 V/m. Electromagnetic fields from high voltage overhead transmission lines are in the region of 2500 V/m at 125 feet and are known to be hazardous to residents living in dwellings directly underneath them." Talbot does not give a reference for this last statement, much less does he cite any dissenting beliefs about electric fields and health. He says electric field strength falls with distance, but gives no idea of how much.

Construction and Air Quality.

All three authors are concerned about air quality but their general approaches to air quality differ. The Baggses and Talbot put their reliance on diffusion and air exchange through the walls. Talbot calls this a "breathing wall." Talbot would rely on naturally present direct diffusion. The Baggses would go so far as to include stimulated natural ventilation (p135), meaning architectural design to take advantage of prevailing winds. This is most applicable in summer or in warm climates.

Bower argues for a house which is unbroken and sealed at the level of gypsum board walls together with a fan to provide a positive air pressure inside the house. This results in air flow being outward so that air pollutants are carried out and never in. He argues that winds are notoriously variable and that on low-wind days reliance on passive methods will lead to poor air quality.

Neither the Baggses nor Talbot express concern for dust per se, although the Baggses are concerned about the dust mites it allows and Talbot mentions dust mites once. Bower, on the other hand, is very concerned about it and calls for a whole house vacuum system to help counter it. He argues that self-contained vacuums used inside the house stir the dust up too much.

The views on plywood are quite different and in an unexpected direction. The Baggses argue that plywood is less than eight percent glue by mass, and that "during manufacture, the resin used to bond the veneer is cured and becomes inert." Their concerns about using plywood are centered on the dust associated with working with it and on its impermeability (p. 156). Talbot, on the other hand, argues that the glues in plywood can exceed ten percent by mass and that excess formaldehyde is used to speed curing (p. 88). Talbot and Bower agree that plywood and other glued-wood products are the leading source of formaldehyde in houses. Talbot regretfully accepts the use of plywood as a subfloor. Bower does not use any glued-wood products.

The approaches to less-processed ("natural") products are also different. Talbot tends to embrace them for reasons outside of health while Bower argues that reactions to chemicals differ considerably between people. For any chemical, whether directly squeezed from a lemon peel or manufactured from petroleum, there will be someone who is allergic to it. He argues that a house needs to be suited to its occupants since it is impossible to build a house that is non-allergenic for everyone. The Baggses vary between these two positions depending on the specific product. For instance, while they consider wood flooring as preferable, they grant that there may be no finish for a wood floor which is non-allergenic for all occupants (p 163).

All three agree that carpets of all kinds need to be kept out of a house. Talbot is willing to use wool rugs and mats from natural fibers such as jute or sisal. Both the Baggses and Bower, having stronger concerns about dust, would not use these either.

For framing, the Baggses and Talbot regard untreated wood as the ideal material. Bower regards untreated soft wood both as termite bait and as a potential allergen and prefers light steel framing. However, as a cost compromise he accepts wood framing for the roof. Here, he says, termites in the U.S. cannot get to it (there are airborne termites elsewhere), so it does not need to be treated against termites. It is not clear to me, given that the framing timbers are outside Talbot's seal, why he doesn't want treated wood.

Paint has been an important problem affecting air quality. The major three options are natural-oil paints, manufactured-oil paints, and water-based paints. The standard varieties of these all have high VOCs. An alternative to all is "milk paint." However, milk paint is a very inviting food for biological contaminants. In addition, some people may be allergic to milk. Bower discusses some new alternatives (pp. 266-267) including formulations which have been designed to be low outgassing and one which was originally designed as a shield against formaldehyde.

The Baggses preference is for wood surfaces that are not painted but treated with sodium carbonate solution so they keep their color. When pushed to choose a paint, they select natural oils, but noting many caveats. Talbot has little trouble selecting natural oils. Bower selects the paint originally designed as a shield against formaldehyde. It is suggested for use with a primer, and he chose to cut costs by using a standard water-based primer. He also takes anything possible outside of the house for painting and leaves it in a garage for a week or two if possible. His choice would be anathema to the Baggses or Talbot since they want breathing walls.

The same fundamental decision about breathing walls or sealed walls also drives considerations of insulation. Bower freely selects fiberglass since the additives are outside his shield and will not enter the interior. Talbot selects cellulose. The Baggses do not make a selection on this issue but discuss the drawbacks of each option in the context of a breathing wall. For cellulose they point out its flammability, for instance. Here and in many sections the experience from designing hundreds of houses in varying situations seems to have led to a smorgasbord of options being presented each of which may be most suitable in some situation.

All three authors describe methods for preventing the entry of radon gas into a house. Talbot is fanatical about radon, deliberately eschewing slab foundation and floor in order to have a crawl space under the floor in which wind can turn over gasses frequently. This is an expensive option. Bower opts for a slab with insurance; a concrete slab is poured over an impermeable plastic membrane which in turn rests on a bed of gravel through which gasses can make their way to the outside of the building. Radon can penetrate concrete due to many small cracks, but it cannot penetrate the plastic membrane. As insurance, he placed a set of pipes in the gravel layer. After the building was finished, he measured the radon level, found it acceptable, and did not install a fan to draw air from the pipes in the gravel. However, he could have if the radon level had been too high. The Baggses describe both slab and crawl space methods for preventing radon danger.

Due to their great concern with electromagnetic fields, the Baggses eschew the use of metal reinforcement for concrete. They thus prefer a wood floor. They are reluctant to give up the heat capacity of concrete, however. Thus, they suggest wood floors combined with unreinforced concrete pads in areas where it can be useful in the winter. They are vague about how to finish a wood floor in a healthy way and seem to suggest ceramic tiles over both concrete and wood (p. 163).

Bower uses concrete floors and tiles. He also suggests wood but points out that oak, the most commonly used hardwood, has tannins which some people are allergic to while softwoods have terpenes. He also does not discuss how to finish a wood floor healthfully.

Talbot relates a number of possible floor coverings. Softwood flooring was used in many of the houses but he does not say how it was finished. Cork was used in kitchens and baths. Tile, wool rugs, and carpet were also used.

Since Bower is concerned about combustion products introduced into a house by use of gas, oil, or wood for heating, he builds houses with all-electric heating. The Baggses are very clear about their avoidance of all electric appliances and suggest a clay oven as the best. Talbot states that use of wood as a fuel is at its pollution maximum at Findhorn, that propane was selected for firing boilers, and that electric stoves were used because they did not have convenient gas supplies. None of the three seems to be concerned about both electric fields and combustion products so there is no discussion of a necessary trade off between these potential problems.

Noise

The Baggses are concerned with noise from outside and describe several means of lessening it. Talbot is concerned with noise from inside especially as transmitted from a second floor to a first, and describes a floor structure that attenuates the internal noise. Bower's ventilation equipment generates noise. He describes steps to attenuate this noise.

Electromagnetic fields

The quotes given to illustrate presentation style also showed the authors' basic orientations towards electromagnetic fields. The Baggses are extremely concerned about them, Talbot is moderately concerned, and Bower is nearly unconcerned.

The Baggses have several subcategories of concern: negative electrostatic fields, natural fields in the 8-Hertz (cycle-per-second) range, and magnetic fields near appliances. They do not mention electric fields near appliances. Talbot's concerns are with natural fields in the 8-Hertz range and with electric fields. Bower checked on magnetic field strengths near appliances.

It is interesting that both the Baggses and Bower reject the use of microwave ovens. Talbot does not discuss them.

The concern which has been tied most directly to health appears to be the natural fields in the 8-cycle-per-second range. Talbot, with no citation, recounts NASA findings that astronauts removed from the Earth's fields experienced sleep deprivation and that an artificial 8-Hertz field restored good sleep. The Baggses cite a secondary source on page 161 (G. F. von Pohl, Georadiation: Source for Illnesses and Cancer) to the effect that steel frames, girders, and reinforcement are associated with "nervous restlessness, headaches, uneasy sleep, sleepwalking, and lack of sleep." Since the wavelength of 8-Hertz electromagnetic radiation is about 100 million meters, any conducting framework for a building-size entity will exclude these fields, and so the claims of poor sleep are consistent with the asserted NASA findings. Neither author provides balanced criticism in their thinking; there is no mention of opposing views. There are common observations that challenge some of the claims. The cited conditions of von Pohl would seem to include the population in New York City, for instance. Is everyone there sleep deprived?

Since Bower uses not only steel framing but also aluminum siding, these fields would certainly be excluded from his houses. On the other hand, the total metal in almost any building, especially the electrical wiring, could easily act to exclude these fields, and I do not understand the Baggses assertion that since earth walls are good conductors, they do not affect the geomagnetic fields. Given the very long wavelength of the 8-Hertz radiation (about one percent of the Earth's diameter), it would also be true that metallic circuits in neighboring buildings or perhaps throughout a city could exclude the fields from a given building. Thus, if this effect is real, it is not clear that implications have been thoroughly considered.

Tables and Resources

The Baggses have a number of tables scattered through the books and several useful tables in the appendices. Bower has no tables. Talbot has a few tables in the appendices.

The Baggses have a number of illustrative diagrams and a lot of attractive pictures of houses. Bower has many illustrative diagrams and many pictures informative of how the construction is done plus, as an appendix, a set of plans for the model house described in the book. Talbot has a few illustrative diagrams and a few useful pictures.

This section presents a review of How Buildings Learn by Stewart Brand (founder of Whole Earth Catalog), Penguin Books, ISBN 0 14 01.39996 6, 1994, 243 pp. with bibliography and index.

The basic thesis of this book is that people want to change their buildings. New knowledge (e.g., about asbestos), new conditions (e.g., changes in energy prices), new technology (e.g., TV, microwave ovens), or just changes in style can drive this desire. So buildings do change. Brand has lots of interesting pictures showing changes that have taken place in buildings.

He identifies six elements of a building which have different rates of change: site, structure, skin, services, space plan, and stuff (listed from least to most rapidly changing).

"Site" refers to the legal boundaries-the element which changes most slowly. This has been shown to survive fire, flood, earthquake, and the end of civilization (in the case where civilization was the Roman Empire). In other words, it doesn't change very fast.

"Structure" refers to the load-bearing elements of the building. They can be changed, but not easily. Changes in structure occur slowly enough to be in competition with the building itself being torn down.

"Skin" is the facade, the appearance. This gets changed on time scales of a decade.

"Services" are the heat, water, air conditioning, television, telephone, plumbing, etc. Technological changes lead to old buildings always being behind the times and getting service changes as money allows.

"Space plan" refers to the interior walls that are not load bearing. Particularly in a business setting, the space plan gets changed quite frequently-with each new management theory. [Bell Labs had totally modular walls; they even got changed with promotions.] Kitchens and baths have been increasing in space inside a residence and centrality of function for the past hundred years or so.

"Stuff" refers to the furniture. It flickers in and out at a rapid pace.

Brand identifies two paths to successful aging for buildings which he calls the "low road" and the "high road." The low road is buildings that start out viewed as disposable. Nobody cares what happens to the building. When it is also easy for the tenants to change it, they do. The result is a building that is changed a lot, that supports its occupants well, and that is not expensive.

If a low-road building incorporates disposability, a high-road building has permanence. It requires structure built to last and a very high finish of skin. It has a sequence of people who care for it extending over generations, especially people who take into account what has gone before.

Architects are part of the problem. They get rewarded for pictures of buildings, not for functional buildings. Frank Lloyd Wright was noted for the leaky roofs of his buildings. He didn't care about that. Brand's comments on domes are interesting: "As for domes, fancied by architects through the ages, the findings are now in based on an entire generation's experience with Buckminster Fuller's geodesic domes in the 1970s. As a major propagandist for Fuller domes in my Whole Earth Catalogs, I can report with mixed chagrin and glee that they were a massive, total failure."

Brand continues: "Domes leaked, always. The angles between the facets could never be sealed successfully. If you gave up and tried to shingle the whole damn thing-a dangerous process with ugly results-the nearly horizontal shingles on top still took in water. The inside was basically one big room, impossible to subdivide, with too much space wasted up high. The shape made it into a whispering gallery that broadcast private sounds to everyone in the dome. Construction was a nightmare because everything was non-standard. . . . Even the vaunted advantage of saving on materials with a dome didn't work out because cutting triangles and pentagons from rectangular sheets of plywood left enormous wastage. Insulation was a huge hassle. Worst of all domes couldn't grow or adapt. Redefining space inside was difficult, adding anything to the outside nearly impossible-a cut-and-try process of matching compound angles and curves."

Brand's take on code is very interesting. He sees the building as an interface between an intense small group inside, and the larger, slower, more powerful community outside. Code embodies what the community has learned. He gives San Francisco earthquake code the credit for limiting the number of dead to 62 in the Richter-7.1 earthquake of 1989 (as compared to 25,000 dead in the Richter-6.7 earthquake of 1988 in Argentina). He was present, helping to save a man and to watch the man's wife die, at a building in the San Francisco earthquake whose bottom story had not met earthquake code. On the other hand, he sees many excesses, especially among homeowners associations in suburbia where covenants, conditions, and restrictions stifle change.

A major influence of the larger community is in lot size. Small lots lead to fine grain adaptation, smaller changes, and fewer changes that are mistakes. He quotes Jane Jacobs to the effect that aged buildings allow people to add money to them incrementally, while new buildings need a huge amount of money at once. She identified the smaller amounts of money as leading to fewer mistakes. There are always mistakes, and when things are tried on a big scale they result in big mistakes.

There is no attractive approach to maintenance so it is not often done well. The two basic approaches are solid construction and preventive maintenance. Solid construction is designing so that little maintenance is required; solid construction tends to be expensive. Preventive maintenance requires routine work on components before they fail; this approach is less expensive but requires discipline.

The root of almost all maintenance problems is water. It consumes wood, erodes masonry, corrodes metals, peels paint, expands destructively when it freezes, and permeates everywhere as a vapor. The vapor from bathrooms, especially in recent, tight-sealed construction, tends to make the bathroom a cancer which metastasizes into the rest of the house. Ground moisture tends to rise and crumble the building from the bottom. But despite this extensive catalog of ways water can attack a building, the main problem presented by water is still from rain entering at the top.

Flat roofs are the worst. They must have a perfect seal to work and perfection is impossible. Worst is that when there is a leak, it is impossible to tell where it is from. The pitched roof sheds water well and provides room for storage or services. Simple roofs are easiest to maintain. Chimneys, dormers, valleys, skylights, etc., invite problems with flashing and make reroofing difficult. Multiple layers, each known to be imperfect, offer protection that one layer striving for perfection cannot.

Wood shingles last only ten to fifteen years. Composition shingles last about five years more. Pottery tile and slate are heavy, expensive, long-lasting, with virtually no maintenance-but they are breakable. They are also fireproof and beautiful. Concrete tiles lack the beauty of pottery tiles but are cheaper. Slate doesn't last as well as tile under the combined influence of sun and rain. Since architects began being sued for leaks, metal roofs have increased in frequency. Stainless steel and copper are the leaders.

After the roof, the windows are the most vulnerable. The catalog of problems presented by windows includes cavities and seals, condensation and moving parts.

Walls have a lot of options, none of which is ideal and most of which have fatal flaws. Aluminum and vinyl siding conceal problems until they fail disastrously. Curtain wall masonry is attached by metal parts which fail in 100 years or less and are virtually impossible to replace. Clapboard looks bad before it is bad but at least it can be painted regularly and replaced piecemeal.

New materials are unproven by definition and, like most experiments, they tend to fail. If used widely, they fail big. Reliance on a single barrier is the key defect of new materials. "That is what made the geodesic dome so leaky." A better approach is multiple redundant layers each of which can be imperfect while a single layer must be perfect.

Wood is wonderful for adaptability, renewability, low price, and beauty. However, it is usually terrible for maintenance. The exception is timber-framed buildings in which the wood structure is protected from the weather, but is massive and exposed. Air keeps it dry, eyeballs keep it inspected.

Brick requires very little maintenance, ages beautifully, and modifies fairly easily. Old brick has a resale value allowing easy recycling. Many designs are possible. Older construction methods avoiding the cavity wall ties need to be used, however, or stainless-steel ties.

Brand's conclusions on maintenance: roofs should be as near to no-maintenance as possible. Walls should be low maintenance rather than no maintenance.

Vernacular buildings are ones built directly from experience with other buildings. This was formerly a regional practice but has become national and international. Vernacular buildings are exceedingly cautious and so immersed in their culture and region that they only look interesting to outsiders. Vernacular builders are glad to accept well-proven solutions to old problems, concentrating on new problems. They become carefully tuned to local weather and society. Vernacular buildings deal in function and form, but not in style.

Three modern vernacular building types have been the Cape Cod, the bungalow, and the mobile home. A Cape Cod house is a one-and-one-half-story box with a large, simple roof-two planes pierced by one chimney. The roof's simplicity makes it cheap to build and easy to maintain. The box can be added on to later. Its low cost led to a revival during the depression. It is a simple, cheap, and growable house. It is respectable but stands aside from fashion.

The bungalow was originally a British import from colonial India, used as a vacation home, hence its name and the name for its most distinctive feature, the verandah. While the verandah was originally designed to keep out tropical rain while encouraging tropical breezes, in Britain and America it became a means of connecting its inhabitants to the outdoors. It can be built on small city lots. A philosophy of simplicity, harmony with nature, and craftsmanship came to be associated with it.

The mobile home has come to be the most house for the least money. It now represents one third of new U.S. single-family construction. Mobile homes are attacked widely-by aesthetes, for housing the "wrong" people, for "unfair" competition to site builders, for not paying their share of local taxes, etc. It has been widely regulated and outlawed, but its use continues to expand. It serves the masses well. The original simple single-wide mobile home has been elaborated into the double-wide and even triple-wide but Brand points out that the single-wide lends itself better to accretion and allows more complex buildings with courtyards.

It is probably not a coincidence that all three of these vernacular designs are small, since small buildings are dramatically cheaper to build and to maintain than large ones. Also, being small, they invite growth.

The home remodeling business has increased rapidly, more than doubling in the past decade. The cash spent on remodeling is about evenly split between do-it-yourself (without labor being counted) and professional (where the labor is counted). Thus more resources are put into the do-it-yourself mode. This activity has become a response to such technological and social changes since about 1880 as city water and gas, lack of servants, electricity and night use, plate glass, concrete, plywood and sheetrock, furnaces converting from coal to gas or oil and freeing basements for use, cars, telephones, television, home computers, etc. Economically the home has been transformed from a production center to a consumption center; however, with the advent of computers this may swing back.

Site-built houses are site rebuildable-one reason they still compete well with factory-built housing.

Nowadays garages have almost anything except cars in them. With the active use of basements and finishing of attics, storage space has dropped, so the cheapest available space, the garage, is pressed into service. There is a clear need for storage space and for undefined space in houses.

Remodeling needs to leave further remodeling easy. In code areas, below code informal remodeling often winds up with a specific professional remodeling which has to (expensively) correct the previous below-code work around it so that the specific remodeling can pass inspection. Built-in furniture saves space but freezes the function of a room and leads to demolishing walls to move furniture. Wiring, plumbing, and ducts need to be kept accessible.

Two chapters of Brand's book deal specifically with how planning can help to make a building flexible. The first suggestion is an import from business strategies: scenario building. Brand has been doing this professionally for businesses recently. The key in scenario planning is to pick a few-perhaps four or five-scenarios which encompass the largest uncertainties; the future is perverse and scenarios seek that aspect of it. Scenario planning lets people consider the greatly different requirements that a building may have to face. "A building is a huge investment, a black tarry pit of sunk costs, a trap, and a prison. The job of scenario planning is to question whether a building is really needed at all and, if it is, to convert it from a potential prison into a flexible tool."

Scenario building suggests oversize structure and services, separation of high and low volatility areas, and different designs. Medium-sized rooms accommodate the widest range of uses. Storage room is always in demand and can become something else easily. Some areas of a building may be highly finished and flashy, others unfinished but useable. The finished areas suggest what is envisioned. The unfinished areas can be finished as experience and conditions suggest is appropriate. This is a Darwinian approach, operating by hindsight (considerably more accurate than foresight).

The other approach is to consider those elements which have in the past led to buildings that can change. An important factor is allocation of resources. For a flexible building, more money allocated for structure, less for finishing, and more for perpetual adjustment and maintenance has worked. A small (or zero) mortgage ultimately frees twice as much resources for the building as compared to a heavily mortgaged building. A potential business is building a minimal but livable core house for about the price of a conventional down payment, then building additions as money becomes available to clients.

Fashion is also an expensive temptation-one tends to buy too much for the moment and pay too much later. "As for shape: be square." The rectangle both grows well and subdivides well. Complications can develop in time. On the neighborhood level, small lots lead to greater diversity in a given area.

Strong structure is almost universal among long-lived buildings. Design for disassembly instead of demolition. Drywall screws are a great invention for disassembly. The classic winner in design for disassembly is post and beam. Walls should be separated from the structure: they are the part of the building most visible and confining to people and therefore most likely to change. Steel studs offer many advantages over wood studs: they don't burn or rot, they are straighter and easier to cut, their weight is one fourth for the same strength, and they stack compactly. Brand claims they are cheaper, but I have seen studies that indicate that, in use, their price exceeds wood slightly. Also, they are new and untested by time which, by one of Brand's main arguments, means suspect.

Services separated from both skin and structure are more flexible. Photos of structure and services before they are covered become increasingly valuable in time. Plans showing what was built (as opposed to what was intended to be built) likewise become increasingly valuable. A log of all repairs is another important document.

Cut-and-try beats planning. Models, larger models, and finally even full-scale models allow people to see and feel what they are planning. Computers have led to more accurate calculation of what structure is needed for the present and consequent reduction; considerable oversizing is better for the future. Undefined space-attic, basement, or storage-is essential.

Living at the construction site is a venerable vernacular practice. There is a need for core starting houses (some of the nicest old adobe houses in New Mexico have railroad cars built into them). These houses are owner-built and designed (it does not pay an architect to design a starter house).

Lasting buildings have high-quality materials assembled with quality craftsmanship. This is expensive, so do it slowly. The fine craftsperson sees code as a minimum, not a maximum.

People are happiest in a building where change occurs at all time scales, from weeks to centuries. A building is never finished, only started.

"Mobile home" is the common term for housing which is manufactured at a factory, towed to the site, and placed more or less permanently on foundations there. Only about two percent of mobile homes are ever moved again. The industry prefers the term "manufactured housing." There is a manufacturer of mobile homes in Austin.

Mobile homes are manufactured as single-wide, double-wide, or triple-wide. The single-wide is up to 16 ft wide, that being the limit for which transportation permits can be obtained. They may be built in sections joined end to end. Double-wide and triple-wide use "marriage walls" to achieve wider houses each part of which can be transported. The single-wide houses are the lowest cost per unit area.

The single-wide houses can be used as "building blocks" to make more interesting houses such as by placing three or four around a courtyard. The manufacturer in Austin said that units without kitchens could be made to facilitate this approach.

The narrowness of the single-wide houses leads to a distinctive appearance. The double-wide and triple-wide houses, while somewhat more expensive, are virtually indistinguishable from standard suburban single-family housing.

Another Austin dealer said they currently have single-wide houses that are 16 by 80 ft with three bedrooms and two baths for $23,000. This would need the 6.5% sales tax, transportation, installation, and foundations costs added to be compared to other options. These would make the cost for this about $30,000. This comes to $10,000 per bedroom or $23.50/sq ft. There are lots of "upgrades" available but it is not clear how many of these are mainly appearance-oriented and how many would make a sturdier house with lower maintenance costs. The addition of a unit without a kitchen could lower the cost per bedroom. It is also not clear how much control over floor plan is available.

The mobile homes can be extended easily horizontally but cannot be extended upwards. They would lend themselves well to tight clusters. However, the narrow width of a single-wide leads toward designs with some of the acreage in a courtyard, reducing the common acreage.

The choice of housing is up to the initial settlers. However, this section presents a conceptual design to see what can be done to build a healthy house on a low budget. This design is more likely to be used in part than in its entirety. Every component of a building such as floors, external walls, roof, internal walls, kitchen, water intake, waste disposal, etc., can be built in many ways. It appears that a low cost and healthy house can be achieved by selecting carefully how each component is constructed.

The basic approach to air quality will be by sealed walls and controlled ventilation rather than by a breathing wall since this gives much more freedom in selecting materials outside the seal. The roof is perhaps the most expensive part of the house, so the house is designed as a simple rectangle to keep the roof design as simple as possible. For a warm climate (mean high in summer 83 F, mean low in winter 45 F), the design needs to consider the summer as much as the winter.

Foundation and flooring

The lowest-cost foundation is a concrete slab which also provides a minimal and non-toxic floor. The cost is about $3/sq ft. This style of construction only works if the frost line is shallow or if the slab is heated. The concrete also provides some thermal mass.

The concrete is not attractive as is and its hardness may be unpleasant, especially where one needs to stand a lot as in the kitchen. Its hardness may be a health problem in that falls could lead to more broken bones. There are no objections to its effect on air quality, as is. There are two kinds of areas to consider, heavy use and wet, and light use and dry.

For a maximum air-quality approach, there seem to be two main options for making the floor more attractive but both leave the floor hard. First, concrete can be made more attractive by adding coloring and texturing. Ocher is a low-cost and effective coloring agent for earth tones from tan through brick red. It costs $10/cu yd of concrete to add it. Being integral to the concrete and being dirt, I don't think there are any health effects.

One standard texture in concrete is achieved by using a broom. More interesting textures can be achieved by rollers or by stamping. The labor cost for a roller is the same as for brooming. Stamping is done using mats with the pattern on them. The mat is laid down and the worker then stands on it. More mats are laid down around the first one. The early ones are peeled off and placed ahead of the working area. Stamping achieves deeper patterns and has about three times the brooming labor cost (although brooming is quite cheap). Common patterns suggest other hard materials such as brick or stone. Texturing requires using a release agent so that the concrete does not stick to the roller or mat. The air quality effects of this are not known but are probably mild. The safety effect of texturing may be negative in that irregularities could cause tripping.

A second, more costly approach is to make the flooring from ceramic tiles. Tiles cost from $1/sq ft to $3/sq ft and take considerable labor to lay. After reading what I can on the Internet, I'm not sure tiles offer much advantage over textured concrete. In particular there is a lot of discussion about maintenance of tiles. They can easily be prettier than bare concrete, of course. In low-use areas the original tile is likely to last a long time and to have very little air quality effect. It would seem to cause safety concerns about tripping similar to lightly textured concrete.

The most comfortable and the best for falls but the poorest for air quality is a carpet. These all have long-term Volatile Organic Compounds (VOCs) and provide a happy home to bacteria, dust, and dust mites among other things. A mat of sisal, tatami, jute, etc. will not have a large VOC problem but will collect dust. Also, fiber mats do not last as long as wool. Wool rugs have some VOCs when they are new but it should be possible to find old wool rugs. They can be taken outside for thorough cleaning once a year. I think this might be the best option to add to a colored and possibly textured concrete floor.

In summary: my choice for low-use areas is colored and smooth or lightly textured concrete plus old wool rugs.

Almost all of the floorings need protection when in a high-use area. The protections generally have some VOCs. For any of the floorings this is not as severe as carpet because they have smooth surfaces whereas carpet with its many threads has a very large effective area. The real problem with these sealants is that they build up slowly from reapplicaction and eventually need to be stripped and replaced anew. In heavy-use areas concrete needs a sealer applied to make it waterproof. The stripping appears to be particularly noxious (sandblasting was mentioned).

There is an epoxy cover that is spread 1/8 inch thick over the base and is very rugged after it dries. Also, it is said to have no VOC emission. It is said to be comparable to ceramic tile in cost considering the lifetime costs, that is, allowing for much lower maintenance cost. This statement is probably based on the more expensive tiles. A further clue that this is expensive is that it meets military specifications and the chief praise for it comes from military customers. The price is estimated to be about $7/sq ft.

In high-use areas ceramic tiles need protection. This protection must be stripped periodically and the stripping appears to be quite noxious. There are tiles made from recycled automobile windows. I have not been able to determine what they cost or what they require for maintenance. They may not need a protective coat. A vinyl covering has VOC problems. This can be ameliorated by leaving it spread out outdoors for a few weeks before using it.

Natural linoleum and cork have been cited as moderately soft surfaces suitable for a high-use and wet area. The cork is more expensive; its specific price is not known at this time. Price of linoleum is also unknown; however, it was considered the low-cost alternative before vinyl came along, so it might cost about 50% more. Both natural linoleum and cork need to be sealed in high-use areas. Linoleum has the advantage that rather than strip it, it would be replaced since its large sheets do not need to be grouted or heavily glued in place.

Summary of guesses for high use areas:

In summary: my choice for high-use areas is linoleum.

Outer walls

The standard construction for outer walls is wood framing clad on the inside with gypsum board. It is clad on the outside by some wood-based material such as oriented strand-board or plywood covered with water-repellent felt paper and then covered by siding which may be vinyl, aluminum, wooden boards, or plywood. The plywood cladding is required for strength if the siding is vinyl or aluminum. It is required for water tightness if the cladding is boards.

A cost-lowering alternative is to omit the outside cladding and felt paper and just use plywood as the siding. This was suggested by Anderson and Zornig of the U.S. Forest Service in Build Your Own Low-Cost Home. Plywood is made with textured surfaces for this purpose. It provides adequate strength and water tightness. It requires maintenance in the form of paint or stain to help it resist damage from water and sun. It can be helped in this also by building the roof with a relatively large overhang. This design plans on this alternative with stain. The stain is preferred over paint because paint is more difficult to maintain although stain needs to be applied more often.

The paint used on the gypsum board is of considerable importance for the indoor air quality. All common paints outgas VOCs. There are recent, more expensive paints which have no VOCs, or sealants with no VOCs. Zero VOC-sealing paints are extremely expensive ($55/gallon). We have chosen zero-VOC paint (non-sealing). The interior paint is about twice normal prices at $16/gal plus shipping.

There are two kinds of barriers that are relevant to air quality, an air barrier and a diffusion barrier. An air barrier stops flows of air. It must be a continuous barrier to do this. Molecules usually diffuse much more slowly than air can flow (consider the air in a balloon, which can flow very rapidly out an open stem or, if the stem is tied, diffuse out gradually through the surface of the balloon). A diffusion barrier aims to slow the diffusion of molecules. It needs low permeability to do this but continuity is not so important. The prototype house we are contemplating is designed with the gypsum board forming the basis of an air barrier. The gypsum board used will be backed with foil to provide a diffusion barrier.

The foil backing on the gypsum board will virtually eliminate diffusion into the house from building materials used outside of it. There are VOCs in essentially everything we design with outside this barrier: the fiberglass, the treated wood, the plywood, and the stains. Positive air pressure inside the house will further reduce diffusion into the house.

The wall cavity is filled with unfaced fiberglass insulation. Since the diffusion barrier is on the gypsum board, none is needed on the insulation. The foil backing on the gypsum board also covers the studs in the walls, which foil on fiberglass does not. Thus it is preferable to have the foil on the gypsum board.

In a warm climate the summer is just as important as the winter in considering temperature. Walls with high heat capacity can even out a day's temperature fluctuations, but this cannot reduce the temperature below the average. The July mean daily temperature is 83.4 F in Austin and there will be weeks with the average temperature in the 90's and days that reach 105 F. We plan to include air conditioning or possibly evaporative cooling and plan on high insulation and a highly reflective roof to keep interior day-time temperatures low. For reference, the mean daily low temperature in Austin in January is 38.6 F and the mean daily high temperature is 58.9 F.

Roof and Ceiling

There are quite a few options for roof type. A very common type is the gable roof which has two shingled surfaces extending down from a ridge running down the center of the building. The lowest initial cost roof is probably a flat roof. Another low-cost roof is the shed roof which is a single, shingled surface extending from a higher wall on one side of the building to a lower wall on the other.

The flat roof is quite difficult to maintain. The underlying reason is that any beams supporting a flat roof will sag at least a little under the load of their own weight and the weight of the cladding and shingles. With wood beams the maximum sagging is typically an inch or less. When it rains, the rain will not run off a roof with a sag. Thus a roof with all its supports at the same height needs to be very well waterproofed.

In northern climates a roof which sheds snow easily is desirable. This leads to gable roofs with a fairly steep slope. The roof also needs to be built stoutly to support a considerable weight of snow until it slides off. These conditions tend to favor the gable roof and variants on it. However, the gable roof requires quite a bit of structure often including a load-bearing wall down the center of the building. This makes the gable roof expensive, but a simple gable roof will be less costly than if the building is not rectangular or if dormers or other structure are included.

In Austin, the largest snow in fifty years is about two inches of snow. Thus a lower slope is possible. A shed roof might do but it seems to be used in short-span applications and we need to span 25 feet. Thus, a moderate-slope gable roof is planned. The key to getting a gable roof with less span than a shed roof is a device called a "joist hanger." This is used in conjunction with a line of walls to support a beam running the length of the building. The joist hanger screws into the beam and provides a cup to support the joist and screws to hold it in. The maximum span is then reduced from the width of the building to the maximum distance between beams.

Code standards for how much a beam can sag are based on supporting the required load while the maximum deflection is 1/240 of the length of the beam. Code tables are constructed for 10-pound-per-square-foot steady ("dead") load plus varying amounts of "live" load to reflect wind and snow conditions. A moderate-slope roof gets a moderate wind load and 30 pounds per square foot is normally used for design.

"Fascia boards" are the boards placed across the ends of roof rafters. "Soffit" refers to the boards placed on the underside of the overhanging part of the rafters. Soffits are constructed with openings for air covered by screen to keep insects out.

The ceiling will be insulated with 12 inches of unfaced fiberglass. The roof will be white to reflect as much sun as possible. The ceiling surface will again be formed using foil-backed gypsum board and painted with zero VOC paint in the interior.

The floor, walls, and roof make one large room. There are various breaks in the gypsum board surface such as windows, doors, vent pipes, and service connections for utilities. There are simple and effective means of sealing each of these breaks. It would also be possible to seal breaks for internal plumbing, electrical, and telephone connections. However, it is planned to keep breaks in the walls to a minimum by running utilities through conduits embedded in the floor rather than through the walls. This not only keeps breaks in the walls to a minimum, but it also allows easy access to existing utility connections and easy addition of further utilities such as a whole-house vacuum system.

Interior Walls

The interior walls are mainly partitions. Most do not bear vertical loads and do not have any utilities run through their interiors. The main consideration for them is to provide a high level of auditory isolation.

Since the interior walls are inside the diffusion barrier, they are made of untreated dimensional lumber. This will probably take a little search but should not be more expensive than treated dimensional lumber. The bottom, top, and ends are made from 2 x 4s. The studs between bottom and top can either be 2 x 3 or 2 x 4, but in either case, they are aligned along the wall, that is, the short dimension is across the bottom plate.

The wood itself (even without treatment) will have some VOCs and if a person is sensitive to them, then the wall can be sealed to reduce the outgassing. This is considered a very minor problem for most people and is not part of the estimated design.

The reason for orienting the studs along the wall is that drywall makes an excellent sounding board and wood transmits sound quite well. Thus, a standard stud-and-gypsum-board wall is nearly transparent to sound. The design here creates a gap between the studs on one side of the wall and the drywall on the other side. This in itself cuts sound transmission a lot. For $0.50/sq ft, these walls are filled with untreated cellulose insulation. This is not for any heat reason but because cellulose makes a good sound absorber. This could be omitted since untreated cellulose burns easily while treated cellulose would have VOCs. Omitting it would make the wall more transparent to sound.

The studs are placed on two-foot centers on alternate sides of the wall. Thus, there is a board to attach drywall to every four feet on each side. The drywall is regular gypsum board without backing and the walls are painted (as are all interior walls) with zero-VOC, non-barrier paints which are twice the price of regular paints.

Utilities

The utilities included were electricity, phone, ducts for intake, distribution, and exhaust, cold-water pipe, hot-water pipe, black-water disposal, gray-water disposal, vents, and propane.

A whole-house vacuum system was not included.

Appliances

The kitchen appliances considered were a stove, a refrigerator, a sink, shelves, and work surfaces. This does not provide for cabinets and it does not include a microwave oven.

In each of two baths the fixtures considered were a low-flush commode, a shower, a sink, and large (wall-size) shelves and mirror. One of the baths has the hot water heater in it.

Assuming that cooling capacity needs to be able to handle cooling from 105 F to 80 F and that heating need to be able to handle from 0 F to 60 F, then we need 22,000 BTU/hr of heating capacity and 9,000 BTU/hr of cooling capacity.

Cost Estimates

The estimated prices include both a 10% contractor profit and a 6.5% sales tax charged on all labor as well as all materials. The house has 2,000 square feet area, six small bedrooms (8 ft by 10 ft), two baths, a kitchen, a storage room, and an air-handling room (for intake, filtering, heating, and cooling). The remaining space is in a large open area. The bedrooms are small, supposing that there would likely be some personal spaces taken from this large room for desks and computers.

Summary of Housing Cost

	cost($)
site leveling	106
floor	6,405
surrounding walls	10,636
roof	12,737
interior walls	9,682
utility connections	6,940
appliances and fixtures	8,204
total	$54,710

This estimate assumes that the construction is entirely contracted out. If some of the work is done by the household, then less cash and more hours are needed.

Some Alternatives to Consider

Eric Hunting

I've found a source for cork, natural linoleum, and non-toxic carpet which we might want to check for prices. It's the Naturlich Flooring & Interiors company of Sebastopol California. Their phone number is 1-800-329-9398 and their e-mail address is nathome@-wco.com. Their wool carpeting is legendary for having survived the World Trade Center bombing, the carpet being used in the lobby shrugging off smoke, water, and an army of repair contractors. They also offer sisal and sea-grass carpeting.

Also, we may do better in both cost and performance using Aircrete or Icynene-sprayed insulation for both the exterior and interior walls. Aircrete is a foamed mineral insulation offered by Palmer Industries (301-8989-7848) that is so non-toxic you can eat it. It's also extremely fireproof and is used in the construction of kilns. It was used for insulation in the Biosphere II complex. Icynene insulation is a water-based variation of polyurethane foam which is noted for its lack of VOCs after initial setting. It is not quite as non-toxic as Aircrete but better-known (thanks to "This Old House"). It is more expensive than fiberglass but the extra cost is supposedly offset by energy savings thanks to its much superior thermal performance. Information on it can be obtained from TWT Construction (914-569-9600).

As for exterior-wall cladding, we may want to look into industrial aluminum- and steel-wall paneling systems. Typically used for commercial and industrial buildings, these are frequently used as exterior-wall and roof cladding in modern-style homes and have some significant advantages. All color is factory applied and the panels are simply cut to length and snaped together to form a water-tight covering. The color is usually a baked enamel which has a low toxicity and an extremely long life. Siding, soffit, facia, and roof-cladding systems are all usually provided from the same manufacturers as part of a uniform intercompatible product line. Though some systems are made to appear traditional in style, these are still best applied to contemporary and modern designs.

Also, I would suggest a price comparison with the Faswall and Hardiplank lines of cellulose-fiber-reinforced paneling products. These have potential as an equivalent-cost, lower-toxicity alternative to plywood where a painted or additional finish covering is to be applied. Hardiplank can be used for wall, floors, sub-floors, and soffits interior and exterior, wet or dry.

As for the use of shed-style roof, you can in fact support a shed roof of much larger areas if you use steel or wood truss instead of plain beams. The approach has been used by a number of contemporary-style architects and seems cost-efficient. Also, I would suggest taking a look at the half-arc roof design as employed by the architects in the Adelaide Ecopolis project (Ecopolis Pty. Ltd.) as well as in the design of Real Good Company's California showcase store. The approach is well suited to the use of more economical and less toxic steel-roof systems and is quite attractive with the right overall design.

Last, I'd suggest a cost comparison with equivalent-sized Linwood Homes (1-800-668-6896) and Deltec circular homes (1-800-642-2508). These kit homes are available with low-toxic exteriors and untreated wood frames at a cost which may be very close to what you've worked out here. Sold unfinished, they would work with the same interior finishing approach. If the cost is close enough, these kit homes could offer a great savings in construction-labor cost because all the major components are pre-made at the factory. I know from my own look at the Linwood catalog that 2,000-square-foot models start in the $53k­$60k range. The Deltec are supposed to be cheaper but I have not yet gotten prices on them.

The basic premises of the Organic Growth House are that a building will grow and change over time and that we do not know what will be wanted in the future. Thus, it is designed as a few very basic parts of a house with those parts overbuilt to allow for expansion upwards as well as horizontally.

The Organic Growth House is based on a Baja-California vernacular style that was mentioned by Brad Woodard. The basic idea of this style is to use trailers as walls for a covered courtyard. (By "trailer" we mean a vehicle which retains its wheels and is at most eight feet wide thus needing no special permit to be taken on roads.)

The covered courtyard of the initial Organic Growth House is designed to evolve into a house. Thus, it starts with about 2,000 square feet and a structure which will let it become a house from which the trailers which originally surround it can be removed. The trailers, however, provide the initial habitable space and are used as one bedroom per person. They also have bathrooms and kitchens. 1970s travel trailers can be bought for less than $2,000 each. Once they have been replaced with interior elements, they can be reused to start another Organic Growth House at the same colony, sold, or used to help start another colony.

The covered courtyard has a colored concrete floor. It has 6 x 6 posts, each on its own pier foundation. They are arranged at the corners of cells which are 8 ft by 10 ft. This is a considerable overdesign for a building of one floor but they will support a three-story building if such is desired in the future. The initial covered courtyard has a width of 30 feet (three 10-ft-cell sides) and a length of 64 feet (eight 8-ft-cell sides).

Beams joining the posts are separate from the joists for the roof. The roof is built in segments which are eight feet wide by thirty feet across. These segments have an individual plywood covering but a shared covering of felt paper and shingles. They have their own beams, joists, and end framing. Again, this roof is a vast overdesign for a one-story building. However, the point is that if one wants to add a floor, the shingles can be removed, then each roof section can be jacked up and a post-and-beam floor built in the middle.

The courtyard roof has a one-foot overhang so that trailers can be parked under it and their doorways will be sheltered from rain. One trailer could be parked on an end and two on each of the long sides to accommodate a household of five.

And that is it for the initial Organic Growth House. Additions that the household might want to consider in the near term would be screens for the courtyard to keep out bugs, sealing the gaps between trailers, and putting up walls where there were no trailers to keep out wind and rain. All additions can be incremental and can wait for funds and thought on what is wanted, since the trailers provide basic shelter.

The Organic Growth House would lend itself very well to building in tight clusters. The ability to build upwards to three floors would allow 300 people on 10 acres if this were the only housing used. The house is wide enough to put bedrooms and bathrooms along the walkway, leaving the living areas, including the kitchen, with the views. The sides along the walkway can be built using metals (steel studs and aluminum siding) to provide a strong barrier to fire.

An Organic Growth House has the lowest initial cost of the three designs considered but would probably have the highest cost in the long term. Including the Texas sales tax of 6.5%, a 10% profit for the contractor, and full overhead and benefits for labor, the cost of the covered courtyard is estimated to be:

The Organic Growth House is then estimated to cost $35,500 initially:

covered courtyard	$25,500
five trailers	10,000
total	$35,500

Each of the houses is estimated without two essential costs considered as community costs, the utility connections and sewage disposal. These are estimated very roughly at $5,000 each. Thus, for five singles, the Organic Growth House would cost about $7,000 initially for the house proper plus $2,000 for community costs associated with the house.

There are a number of alternative construction methods that are being discussed and tried these days. We have looked most closely at those which attempt to get a low cost. The low cost usually turns out to mean a low materials cost and the possibility of owner labor to build with the system. The failure to price labor is a mistake economically since it effectively sets the price of labor to zero and leads to misallocation of labor. The alternatives considered are domes, earthships, strawbale, adobe, cob, and gunite.

Domes: There is a nice web page at http://www.monolithicdome.com/ which shows that there are commercial dome building systems now available. The page has little information on price. One newspaper-style article states that dome construction reduces prices by $5 per square foot compared with standard construction. Since standard construction is about $75 per square foot, this is not much reduction. A close examination of the dome building techniques suggests why. They need to use rebars in the concrete of the dome and these are specially shaped rebars to make a series of successively smaller circles up the dome. The circular concrete flooring takes heavy reinforcement around the edges to resist the outward thrust of the dome. Thinking about these domes led to noticing the external similarity of the Poly-steel structures.

Earthships: There is a bit on the Net about these. Search on the word "earthship." They are built into a hillside using earth rammed into discarded automobile tires. The south-facing front is glazed. These are very attractive ecologically and visually. However, the earth ramming is labor-intensive. The Websites have several statements on the cost of building an earthship and they agree that the cost is comparable to standard construction.

Strawbale: There is a mailing list devoted to this construction technique. It is only different in how the exterior walls are constructed. Prices for construction given vary from below average to above average per square foot. The difference is in how much work is done on the inside. Apparently, code-meeting construction is about average in price.

Adobe: Adobe is suitable in an area of the country which is quite dry. It is labor-intensive, as are earthships, and is distinctive mainly for the outer walls as are the strawbale houses. The result is a construction technique which, when labor is paid for, gives a higher price per square foot than standard construction does.

Cob: Cob is a similar technique to adobe but it avoids the brick-making stage, applying the earth and straw mix directly to build up walls. It can also be used for built-in benches and ovens.

Gunite: Gunite is sprayed concrete. It can be sprayed over welded-wire sandwich panels as a way of building a house. The panels are foam with welded-wire fabric held about three quarters of an inch off each surface. They are easy to assemble into the frame of a house and can then be sprayed with concrete (gunite). An article by a practitioner in Concrete Construction, 1993, p. 798, suggests that houses can be built at low cost using this technique. However, the discussion is about the rising cost of wood and how this technique is becoming economic. Thus, the savings would not appear to be large. Also, an evaluation of this, foam core panels, and light-gauge steel framing concludes that all are more expensive than standard wood-frame construction.

contact the webmaster: Dmitri Donskoy Last modified: Tuesday, December 8, 1998

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