The amazing ancient modern building material that improves the environment every time it is used

Architect Stephen Colley, coordinator for San Antonio Sustainable Living spoke at the 2010 TEDx San Antonio.  In his talk he introduces the audience to adobe and compressed earth block.  He explains how the words adobe and shack connect the material to its historic roots.

He shows how adobe and compressed earth block allows for deeply green, environmentally and physically friendly building. He explains the phase change that makes adobe homes cooler in the summer and introduces the so called "Mexican green roof" which insulates, protects and cools.

Compressed Earth Block Workshop

Once every year or two in Central Texas, there’s a premier opportunity to learn all about compressed earthen block (CEB) construction, lime stabilization, and natural finishes. That opportunity returns for three days in May (20-22) here in San Antonio. Jim Hallock and Jeff Rottler from Tierra y Cal, from San Miguel de Allende will offer a very comprehensive class in CEB covering all aspects to consider. If you are thinking green building, building a durable, healthy, high-performance structure doesn’t get any greener than using the earth. Partnering again with Laurence Jetter of Advanced Earthen Construction Technology (AECT), here in San Antonio, Jim and Jeff will be incorporating the best technology in compressed earth blocks available. For more information regarding the agenda and registration details, contact Tierra y Cal directly at their website.

Building with Awareness: the construction of a hybrid home

In south Texas, some potential owner/natural homebuilders have decided that neither a strawbale nor an adobe/compressed earth block house is right for our climate.  The solution is a hybrid home which appropriately combines strawbale and blocks for thermal mass.

In the DVD and accompanying book, Building with Awareness, Ted Owens documents the building of a hybrid home in New Mexico, (which of course imposes very different climate challenges than those encountered in south Texas.)  This hybrid home combines exterior strawbale construction with interior adobe for thermal mass. 

The video is available for purchase or Netflix customers may add it to their queue.


Below are the trailer and a six minute excerpt.

Even New Mexico regulators don't understand adobe!

In New Mexico they have adobe brick factories for goodness sake. You'd think that the regulators would understand the energy efficiency of the stuff and the value of adobe to the state's economy and environment, but according to the an article by Joe Tibbets in the July 2009 Solaradobe Newsletter from SWSA Adobebuilder.com, the state's Energy and Minerals Department is pushing for adoption of the a national code which does not:

1. Does not mention any passive solar in its calcs
2. Cannot model passive solar well
3. Does not have the sophistication of Energy 10
4. Cannot integrate thermal mass or temperature swing
5. Cannot program Trombe walls or time delay
6. Cannot program selective surfaces or reflectors
7. Leans designers away from passive solar
8. Leans designers to expensive equipment that needs government subsidies
9. Requires 'energy experts' to use REM software to review drawings for permits
10. Calls for REM to be a requirement in new green building codes

Courtesy Solaradobe Newsletter

The code they are pushing which incorporates HERS ratings and LEED standards would substantially upgrade the efficiency of inherently inefficient construction methods (stick building) but would cause problems for adobe and compressed earth block builders among others, since according to Joe adobe builders would not qualify for the NM Sustainable Building Tax Credit.

This illustrates how complicated regulatory issues can become. Good luck to all the natural builders in New Mexico.

Photo courtesy Leto A. by CC license and Flickr

Stephen Colley's presentation on Adobe, Mason Greenstar papercrete and clay finishes as filmed by OrganicTexas posted to YouTube

Jason of OrganicTexas brought his camera and crew to the June meeting of San Antonio Sustainable Living at Whole Foods. The resulting video, divided in to YouTube compliant lengths has been posted to the web.

Architect Stephen Colley, AIA talked to the group about adobe construction, clay finishes and building with Mason Greenstar papercrete blocks among other things.

If you follow the OrganicTexas link to the San Antonio Sustainable Living playlist you can play all of the segments in order.

Five things I learned at the June San Antonio Sustainable Living group meeting

Our June meeting featured Stephen Colley sharing information from several recent conferences he attended. Below are several things I learned from his talk and from those of other attendees.

1. George Strait, real famous country music singing star, has a genuine adobe in the Dominion on IH-10. It is visible at a distance, since it is on top of a hill, but of course you can't get in to see it without his permission.
2. However, Adobe Village on Hwy 281 just north of the River Crossing subdivision in Spring Branch has six genuine adobes which are open to the public, in fact they want you to come visit. I think I have seen them for a year or more, but I always suspected that they were only faux-dobe.
3. Ground glass from municipal recycling is piling up awaiting buyers. Tim White of Roman Stucco has found that when it is ground properly it can substitute for coarse sharp sand in stucco.
4. A lime clay plaster finish known as Tadelakt is nearly waterproof and can be used to line showers and for backsplashes.
5. The AIA (American Institute of Architects) is very involved in Architecture 2030, which according to the website is an attempt to "rapidly transform the US and global Building Sector from the major contributor of greenhouse gas emissions to a central part of the solution to the global-warming crisis."

The John J. Morony Studies: "Adobe and Latent Heat: A Critical Connection" (Why Adobe is cooler in the summer and warmer in the winter)

John J. Morony's original, controlled research has shown that the perception that adobe buildings are more comfortable than others has a factual basis. At the Tierra y Cal workshop, June 13 he generously gave our group permission to reprint on this site the studies he distributed to participants in the workshop, including this one.

Some of the graphics may not be clear in this blogged version. Mr. Morony is not responsible for any errors in this presentation of his work. Please contact Mr. Morony for a copy of his study in its original format.

Adobe and Latent Heat: A Critical Connection
John J. Morony
Department of Biology
Southwest Texas Junior College
Del Rio, TX 78840

Mailing Address:
P.O. Box 421627
Del Rio, TX 78842

Abstract

A series of ongoing experiments provide evidence supporting the oft-told adage that adobe houses are "warmer in the winter and cooler in the summer" than houses made of other materials. Two modular structures of equal dimension, one of adobe and the other of cinder block, were constructed with 8-inch thick walls, and roofs and floors of identical material. Each structure has an identically constructed and fitted small door for entry of data-gathering instruments. Simple experiments illustrate the thermal properties of adobe (i.e., soil). Adobe still remains soil after its incorporation into a building and thus adobe has the thermal dynamics of soil. Phase change from liquid water to vapor or the reverse will result in a high rate of latent heat to lower or raise the temperature of adobe.

On a dry day, with an out door ambient temperature of 98ºF, interior temperatures were 90ºF in the adobe structure and 103ºF in the cinder block structure. It is proposed that the 13º variation in temperature in the two structures is a direct result of the adobe having lost 8º by way of latent heat of vaporization (in accord with known properties of soil), whereas the cinder block structure gained 5º due to simple heat conduction. The reverse occurs when relative humidity is high and temperatures are low. Adobe then takes in moisture from the air, thus releasing latent heat. During cold weather, data loggers for temperature and moisture were placed in each of the modules for ten days. During each diurnal cycle the lowest and highest temperate were restricted to the cinder block.

Clay, the binder in adobe, is hygroscopic and its water content varies with available moisture. Such variation precludes adobe being assigned a specific heat capacity comparable to conventional building material. More importantly, any evaluation of adobe needs to take into consideration dynamic properties of soils (especially the role of latent heat) and not be restricted to the parameters of sensible heat (a static property) by the building industry. Experimental data gathered by the author provides strong evidence that as a construction material adobe blocks keeps a building warmer in the winder and cooler in the summer than cinder block. The explanation for this phenomenon appears to lie in the role of latent heat, not sensible heat -– a critical distinction.

Introduction

Use of cinder blocks for construction of small buildings, especially housing, has almost completely replaced adobe along the Texas-Mexican border. In the Mexican city of Ciudad Acuña, across the river from Del Rio, Texas, perhaps as much as 95% of new home construction, and essentially all government built houses, are of cinder block.

This trend from earthen structure to a cinder block one appears throughout the non-industrial world. Even still, in land where adobe construction had once dominated, the belief of the older populace persists: "Adobe is cooler in the summer and warmer in the winter."

The means for temperature moderation in adobe houses may come from the ease at which moisture enters and leaves permeable and hygroscopic soil in response to changing atmospheric conditions. The movement of moisture in and out of the adobe is more than a simple transfer of water. It is the transfer of latent heat that must take place when there is a phase change in water that raises or lowers the temperature of the building fabric. While adobe and compressed earth blocks have been assigned an R-value of .25/inch, it is the latent heat exchanges that appear to be the dynamic factor to consider most when comparing it to other building materials.

Adobe differs profoundly from all other type building material in that adobe comes from soil and remains soil after its incorporation into a building. Latent heat flux is of elementary concern to soil science. Attempts to evaluate adobe exclusively in terms of sensible heat, as with the use of the R-value, or thermal mass, have resulted in confusion in evaluating abode in terms of thermal properties.

Adobe and its suitability for exceptionally hot climates (as exists along the Texas-Mexico border) are of special interest to this study. Traditional concerns in the United States have been for development of building materials for use in cold climates. Adobe vs. cinder block construction is being studied with a series of simple experiments including the use of two modular structures, one of cinder block and one of adobe. Studies were conducted in Del Rio, Texas in 2003 and early 2004.

Two Modules

Experiment 1: Two modular structures with 8" walls were constructed: one of adobe blocks (8" x 16" x 4") and one of cinder blocks (8" x 16" x 8"). The cinder block was stuccoed with cement and the adobe with lime. Both were left with their natural color. Outside dimensions of both modules are approximately 62" x 48" x 26" with interior volumes about 22 cubic feet each. The roofs and floors of both are constructed of the same material. Both face west and were free of shadows throughout the day (Figure 1). Recording of data was made 27 August 2003 at 4:30 p.m. Modules are located at the Casa de la Cultura in Del Rio, Texas.

Figure 1. Experimental modules. Cinder block left and the adobe on the right. With ambient temperature of 98ºF, temperatures inside the modules were 103ºF in the cinder block and 90ºF in the adobe (13º different.) The cinder block was 5º above ambient and the adobe 8º below ambient.

Reference to R-values, or thermal mass, cannot fully explain the 13 degree difference in interior temperature. An 8-inch adobe wall has an R-value of 2 (0.25/inch for adobe) and the cinder block used has an R-value of 1.08. With the lower R-value, the cinder block would be expected to exhibit a higher interior temperature; however the significant difference is that the cinder block was above ambient temperature whereas the adobe was below ambient. This indicates that there is another important contributing factor beyond the insulating properties of these materials.

Experiment 2: Data loggers were placed in the two previously described modules during acute cold weather from the 25th to the 30th of January, 2004. Data was recorded for temperature, relative humidity and dew point. Only temperature data is illustrated in Figure 2a and 2b.



Figure 2a. Temperature data loggings during a cold period (25th to 30th of January 2004). The solid bold line represents adobe; the dashed line represents cinder block and the solid light line represents ambient temperature. Note that for every temperature extremes the cinder block had temperatures higher and lower than the adobe. Also fluctuation of temperature was greater for the cinder block than for the adobe.

Figure 2b. Enlargement of the data on a cold day (January 27, 2004). For that day, the range of temperature was 12ºF in the adobe and 24 ºF in the cinder block.

Experiments on Latent Heat of Vaporization/Condensation

Effect of latent heat, especially of vaporization, is first demonstrated with simple experiments prior to more discussion. The initial experiment relates the nature of clay and the permeability of clay-rich material to observed results of evaporative cooling or latent heat of vaporization under full sun.

Experiment 3. Four small plastic flower pots are used to demonstrate that heat of vaporization moderates temperature. Three red clay-colored plastic pots and one slightly larger red clay pot were used. One plastic pot was painted black, another painted white and the third was left its original color. The clay pot is left with its natural clay color. The pots had their bottom holes sealed. Each was filled with 500 ml of water and covered with a corresponding colored plastic lid and placed in full sun. Ambient temperature at the time was 94ºF in the shade. After being left in full sun for three hours (2:00-5:00 p.m. CST), data were recorded (Figure 3.)

Figure 3. Test flower pots and vaporization of water. Ambient temperature was 94ºF.

Pot 1 Black, 113° F + 19° difference. (No measurable loss of water)
Pot 2 White, 102° F +8° difference (No measurable loss of water)
Pot 3 Natural Clay Color, 105° F +11° (No measurable loss of water)
Pot 4 Clay Pot, 86° minus 8° (56% loss of water)


The most dramatic difference is in the temperature of the clay pot; a full 8º below ambient, whereas all the plastic pots were well above ambient. The clay pot was 19º cooler than the plastic pot of similar color. Also of note is the large amount of water lost from the clay pot. An explanation is that the clay pot, while being waterproof to liquid water, it is permeable to water vapor that readily diffuses through the sides of the pot. Such movement of water molecules involves a phase change from liquid to water vapor, resulting in the latent heat of vaporization. For each gram of water going from liquid to a vapor state about 580 calories per gram of heat (540 calories per gram for vaporization with the boiling of water) are removed from the clay pot. As the clay pot lost 280 ml of water (one ml of water is equal to one gram) by diffusion there was a total of some 160,000 calories of heat removed from the water! As the heat lost is incorporated into the vaporized water molecules, it is not subject to measurement by a thermometer nor can it be felt -- it is thus 'hidden' heat or latent heat of vaporization as opposed to 'sensible heat' (heat that can be felt and measured).

The plastic pots, being impermeable to water vapor, evaporative cooling was not possible. The difference in temperature of the plastic pots is associated with differing capacity of colors to absorb solar radiation. Black mostly absorbs radiant energy while white mostly reflects it. The rather dark natural clay color is in-between. The contrasting colors of black and white pots translate into difference in temperature in the two pots of 11 degrees.

Experiment 4. The important role of clay and aggregates (sand and silt) in adobe are demonstrated with a simple experiment. Besides serving as the binder in adobe, clay also contributes important thermal dynamics properties. There are two factors to consider in relationship to this: clay particles carry a negative charge and thus water, a polar compound, is readily attracted and attached to clay particles; and simple diffusion of water vapor from high to low concentration varies throughout the day in response to changes in atmosphere moisture. The presence of aggregates in the adobe provides pathways for capillary action, allowing water molecules to move in and out.

Figure 4. Moisture absorbed by clay in response to changes in relative humidity. The result in exposing a cube of a compressed earth block to conditions of a hot dry climate (Del Rio, Texas from August to 20 to 24, 2003.) Weights were recorded in early morning and late afternoon.





Percent of weigh gain may be small, but the latent heat of vaporization that it represents is extremely great. The specific heat of water is much higher than any conventional building material.

Experiment 5. Three clay pots were used to determine the effects of color on evaporative cooling. One pot was painted with white enamel, one with white lime wash and the third was left its natural clay color. The bottoms of the pots were sealed, the pots filled with water, covered with a cap of similar color and placed in full sun. Any differences in evaporation between the while colored posts, related to the nature of the coating material, will be revealed.

Figure 5. Small clay flower pots filled with water: #1 lime wash; #2 enamel paint; #3 unpainted clay color. Pots exposed to full sun with for three hours in late afternoon. Ambient temperature of 94ºF.



The limewashed clay pot is now 16º degrees below ambient temperature! The high reflectance of the white limewash significantly limits the amount of radiant energy absorbed to convert into thermal energy as sensible heat. At the same time, lime remains vapor permeable and thus permits evaporative cooling.

The white enamel on the pot succeeds in greatly reducing the conversion of radiant to thermal energy, but because it is impermeable to water vapor it prevents evaporative cooling.

Experiment 6. Three clay flower pots were used to determine the effects of color on temperature when no evaporative cooling was allowed to occur (Figure 6.) One pot was painted with white enamel, one with white limewash and the third was left its natural red clay color. The pots were placed upside down in full sun. Inside temperature was measured with a thermometer inserted in the hole in the bottom of the pot.



Figure 6. Large clay pots turned upside down exposed to ambient condition in full sun; #1 enamel white; #2 white limewash; #3, natural clay color. Inside temperatures recorded after three hours exposure and subsequent gain in temperature is recorded. Ambient temperature of 94ºF.




Note that the limewash is highly effective in reflecting solar radiation. Limewash is a mixture of slaked lime (calcium hydroxide) and water. When applied as a near water-thin paint it sets slowly by absorbing CO2 from the air, producing crystals of calcite (CaCO3, calcium carbonate). Unlike paints that are organic polymers, limewash is a mineral of dual reflective index and thus more effective in reflecting solar radiation. The limewash is 6º lower than the enamel.

Latent Heat and Building Materials

Phase change material (PCM) is any substance capable of latent heat flux and it has been of interest to the building industry since at least the 1940s. Stored energy in latent form within a building fabric would lead to greater heat storage capacity per unit volume than would be otherwise possible with conventional building materials. The concern has focused almost entirely on providing warmer indoor temperature in the winter. Interest in the matter appears
to have been restricted to heat of fusion and an inventory of PCM did not include soil. It was initially restricted to a list of inorganic chemicals (largely hydrated salts) that would have to be incorporated into a building fabric and none constituting the building fabric itself. Nothing really workable emerged from these efforts. Interest then turned to organic PCM but with like consequences.

Soil, suitable for earthen block making, is inherently phase change material par excellence. Most significantly, it constitutes not only the entire building fabric as to heat of fusion but to vaporization and condensation as well -- and it does so to a degree far in excess of almost all other materials man-made or otherwise.

The Nature of Adobe vs. Cinder Block

Clay is the binding material of adobe with silt and sand serving as the aggregate, often with the addition of fibrous organic matter by way of straw or horse manure. In construction of an adobe block, clay remains chemically unaltered. Adding water serves to facilitate rearrangements and compaction of the particles in making adobe blocks. The clay in the adobe block retains its capacity to attract water after the block is made. This water can move in and out via capillary action in response to available moisture along the pathways created by the contained aggregate.

In contrast, Portland cement (a highly complex and altered very fine powder predominantly limestone) undergoes a chemical transformation into concrete when mixed with water and an aggregate. While some capacity for capillary action may remain, it is much reduced compared with adobe or other earthen building materials. Importantly, the clay content of Portland cement has been chemically altered and is no longer hygroscopic. This distinction between earthen material and products incorporating Portland cement (or stone and brick for that matter) as building material is critical to appreciating their thermal character.

A Scaled-up Model to Consider

To scale up from the small modules, previously discussed, an appreciation of the thermal properties of an existing adobe dwelling is provided by a study published in Earthbuilder (10th Anniversary Issue 42, 1984, p. 56, Adobe News, Inc.) The house, described as an "old style adobe", was located in Los Lunas, Rio Grande Valley, New Mexico at an elevation of 4,750 feet. The building had 17-inch thick walls and an 8- to 12-inch thick earthen roof. Temperature was recorded in two intervals: before and after expansion to the house. The initial floor plan, of less than 1,000 square feet is illustrated below (Figure 7)





Figure 7. Original floor plan as of June 14, 1976. No insulation was used and no cooling mechanisms or overhangs existed. There was one window on the north side. Late in the day a large tree partially shaded the northwest corner of the house. The building was kept closed during the period the data was gathered.

Temperature data for the adobe house on June 14, 1976:



Inside temperature of the adobe did not exceeded 80º F when outside temperatures average in the mid- to upper 90s. Note that when outside temperature was 102ºF, inside temperature was 80ºF (a 22º difference!) The authors state that there was an inside temperature variation of only 5º in the house from May 27 to July 11 of that year, and further note that this was with no roof insulation or cooling unit of any kind. Significantly, the authors comment that it was noted that the inside high temperature occurred during the morning hours, at roughly 12 hours after the outside high of the preceding day. Likewise, the inside low temperature appeared in mid- to late afternoon, roughly 12 hour after the morning outside low temperature. That inside temperatures of an adobe house would be cooler when outdoor ambient temperature is highest and warmer inside when outdoor temperatures are coolest is clearly counter-intuitive! However, the adobe is responding not to sensible heat of the environment, but rather to a differential of moisture content on either side of an adobe enclosure.

Latent heat of condensation would be expected to occur in the morning hours when relative humidity is highest and outside temperature is coolest. The absorption of moisture by the clay in the adobe would result in raising the temperature of the adobe. In the late afternoon, when relative humidity is the lowest, latent heat of vaporization (evaporative cooling) would exhibit
a reverse effect, i.e., adobe would actually cool. However, the explanation provided by the author centered on what is said to be the 'flywheel effect'. This is an untested assumption that a delay in the conduction of heat in and out of the adobe house would be due to sheer mass of the wall. A question arises: what is the annual energy cost required to maintain a comparable inside temperatures of a building not susceptible to latent heat flux?

Summary

The preliminary results of a series of ongoing experiments may be summarized as follows:

1. Adobe is indeed cooler in the summer and warmer in the winter, and significantly so, in comparison to cinder block and other non-earthen building materials. The reason for this is not directly related to sensible heat of conduction, but rather to latent heat and especially latent heat of vaporization and condensation. Latent heat flux appears to stabilize internal temperatures within an adobe enclosure.

2. Thermal qualities of adobe and other earthen materials cannot be accurately expressed or understood using only the R-values of conventional building material. The "guarded hot box", used to determine the R-values, measures steady-state heat flow of differential heat on either side of the material being tested. For adobe, it is the latent heat flux promoted by a moisture differential on either side of a wall of an enclosed adobe building that lowers and raises the temperature of the adobe. The concept of insulation, as it is applied to conventional building materials, is of doubtful use or significance.

3. Caution is suggested in the use of any material, modifications or structural design that might impede the thermal dynamics of latent heat flux of earthen structures.

4. Latent heat phenomena would appear to strongly favor what has come to be known as a "green roof" for adobe structures.

5. Adobe and similar materials must be recognized for what they are -- a very superior building material both from the standpoint of their functional value and cost. Economically, the price of soil is not tied to the price of oil, and the costs for heating or cooling would be significantly reduced in a rightly constructed earthen structure.

The John J. Morony Studies: "Adobe Moisture Absorption and Temperature Control" 2005

John J. Morony's original, controlled research has shown that the perception that adobe buildings are more comfortable than others has a factual basis. At the Tierra y Cal workshop, June 13 he generously gave our group permission to reprint on this site the studies he distributed to participants in the workshop.

Please contact Mr. Morony for a copy of his study in its original format.

Adobe Moisture Absorption and Temperature Control

Logged Data for a Humid Heat Wave 6-11 August 2004
Del Rio, Texas
John J. Morony
Biology Department
South West Junior College
Del Rio TX 78840

Abstract

Logged data of temperature and humidity were collected inside two modules, one of compressed earth blocks (CEB) and one of cinder blocks; each is some 20 ft with identical roofs and floors. With an ambient temperature of 106 F the cinderblock module was 110 degrees F and the CEB was 101 degrees F or 9 degrees cooler. When the ambient relative humidity (RH) was high the inside humidity of the cinder block approached 100% but in the CEB the RH did not exceed the mid 60% mark. The lower RH is explained by the moisture being absorbed by the earthen walls. This suggests the possible use of evapor4ative coolers in buildings constructed of an earthen fabric in regions where evaporative coolers tend to build up too much humidity for human comfort.

Introduction

A previous study (Morony, 2005) revealed that adobe and other unmodified earthen material, undergoes latent heat flux in response to differing states of relative humidity within and without an adobe building. In such instances, adobe walls may be absorbing and passing moisture vapor on the either side of an adobe fabric provided the walls remain free of vapor barrier covering. This study presents specific evidence that such phenomenon does indeed occur.

A series of on-going studies is being conducted in Del Rio, Texas of indoor vs. ambient temperature of earthen building fabrics and concrete (cider) blocks. Modules of similar dimensions are used in conjunction with data loggers to record temperature and humidity. The principle focus of such studies concerns the response of varied building fabrics to prolonged summer heat characteristic of south Texas. It is summer heat and not the winter cold that intrudes into the human comfort zone and it does so to the point that air conditioning is required. Refrigerated air is used every month of the year every hour of the day for some months running. Air conditioning is currently the only effective, but very expensive means, to significantly lower the indoor temperature to the comfort zone (temperatures below 80 degrees F) . Air conditioning is often the most costly item on the monthly energy bill for a significant part of the year.

Procedures

Three modules, numbered on the north facing wall as #1 to #3, are illustrated in the frontispiece. They were built in 200-4 on property adjacent to the Southwest Texas Junior College campus in Del Rio, Texas. All have six inch thick walls (not including stucco) and inside dimensions of approximately 35" x 42" x 25.5 " resulting in an internal volume of ca. 20 cubic feet. All face north and have a single opening on the north side with a door and a latch. The modules are not intended to be air tight, thus allowing equalization of changes of atmospheric pressure. All are fully exposed to the sun throughout the day. The modules have a flat roof covered by 3/8 inch panel board insulated on the under-side with an sheet of Energy Shield, a product of Atlas Roofing, that is a foil faced foam board with an R-rating of 5.4. A sheet of this foam board is also used on the floor of the modules.

Module #1. Six-inch Mexican concrete (cinder) blocks were used in the construction of the module. The module was stuccoed with cement and painted with an off-white cement paint to match the color of the two lime stuccoed earthen modules.

Module #2. Traditional adobe was used with an appropriate soil mixed with horse manure.

Module #3. A compressed adobe (or compressed earth block) structure. 6 x 12 inch, using the same soil as was used to make adobes of Module #2 but without additives save moisture. Blocks were made using a CINVA Ram, a hand operated machine using mechanical leverage to exert pressure.

Data Logging

VERITEQ data loggers, Spectrum 2000, were utilized inside the modules and set to record temperature, relative humidity every three hours continuously during the time of the experiment. Doors were kept closed at all time. Temperatures were read to the nearest whole number.

Data loggers were used in Modules #1 and #3 only during a period of prolonged hot and humid conditions from the 6th to the 11th of August, 2004 in Del Rio, Texas. A separate data logger was used to record ambient condition in the immediate vicinity of the experiment for the same time intervals as used in the modules. Results of the data logging a recorded in Figures 1 and 2.

Temperature Data (Figure 1). The cinder block module recorded temperatures higher than ambient during the highest temperature values for the 6th, 8th and 10th of August (Fig 1). During the same time intervals the compressed adobe was always significantly lower than ambient. Highest temperature for each of the three recording are: Ambient 106 degrees, compressed adobe - 101 degrees and cinderblock- 110 degrees. Thus the compressed adobe registered some 9 degrees cooler than the cinderblock module. These data are in accord with similar type studies by the author using these and other like modules. Cinderblock modules were consistently higher in temperature than highest ambient temperatures during hot weather. Residents living in cinderblock homes on either side of the Rio Grande River report higher indoor temperatures than outdoor during high heat conditions. However, the significance of the temperature data is heightened when taking into account concurrent humidity data.

Humidity Data (Figure 2): There was a pronounced rise in humidity in the cinderblock module during a prolonged hot an humid period from the 9th to the 11th when the experiment was terminated. On the 10th, when the cinderblock was 100 degrees F the RH was some 90% then peaking at near saturation. Residents of cinderblock houses along the Border report high humidity and module growth during certain times of the year, especially lat spring and summer. In marked contrast, the RH in the compressed adobe remained below mid-60%. An explanation is that the clay content of the earthen walls succeeded in absorbing a major portion of the accumulated moisture. Thus, a plausible explanation for the lowered interior humidity of the adobe module was that the water vapor was absorbed by the walls. There are important implications to be considered. Perhaps foremost is the need to avoid a wall covering, especially a render or plaster that would interfere with vapor transfer into or out of the walls.

Discussion

Why the profound difference between the adobe and the cinderblock with respect to humidity and temperature? In essence, adobe and other type of earthen material, left unbaked or stabilized, constitutes phase change material (PCM) ; a terminology of the building industry. The term applies to any chemical substance deemed useful for temperature control for some industrial purpose (Ruth Kelly, 199). The nature of phase change phenomena was explained at length in a previous publication (Morony 2005). All mater is subject to existing in one of three phases: solid, liquid or vapor. A phase change from one to the other either releases or absorbs thermal energy in response to critical temperature changes.

An explanation centers on the hygroscopic (water attracting) qualities of clay in the adobe. The clay carries a negative charge and bonds with the positive pole of a water molecule. Clay is thus capable of absorbing water in a vapor phase as well as liquid. Phase-change of water form solid/liquid and from liquid/vapor results in an exchange of thermal energy. In the case of liquid/vapor changes the energy involved is very great relative to the phase-change in other chemical compounds. In a liquid to vapor change of on kg of water at 100 degrees C converts to 2260 kj/kg of heat (540 cal/gm) that is released to the surroundings (P. Hewitt, 1981). while cinderblocks and other conventional building material my readily absorb liquid water, as with rain, by way of capillary action but it is other wise with respect to atmospheric water vapor.

The aforementioned qualities attributed to adobe apply as well to clay plasters as detailed in a study by Neil May (2004, p2). He noted that clay plasters absorbs ambient moisture an that the hygroscopic qualities of clay "...means that moulds caused by condensation are minimized, and that a relative humidity of 50% -60% is maintained. This is the ideal level for mucus membranes of the human body and also for the control of dust mites and other organisms which affect human health." Additionally, he notes clay plasters have very good capillary qualities but less capillary draw than materials like lightweight brick, and even certain cement products. However, they have more capillary draw than most types of timber. They thus draw condensed water away from a timber frame building but will not dry out the timber itself.

Temperature and Humidity

To what extent can the temperature and humidity be lowered inside an earthen residential structure with minimal expenditure of energy? In South Texas the problem with evaporative coolers is t that excess humidity tends to build up creating conditions for mold growth and is uncomfortable to a building’s occupants. However, resorting to the use of refrigerated air in summer months is generally the most expensive item on a monthly utility bill. One may thus ask, what would be the consequences of using one of the newer, highly efficient, evaporative coolers within and adobe building? A sustained build up of humidity on the inside would be prevented. the earthen walls would absorbed excess humidity at the same time the interior temperature would be significantly lowered. However, it is important to note that for latent heat flux to occur an earthen building fabric would have to remain free of vapor barrier on either side. Additionally, efficient evaporative coolers , that use direct current, are available that can run off a 12 volt solar panel to be used in the afternoon when RH is lowest. Currently, the Adobe Association of Del Rio (Texas) is in the process of constructing a small experimental building to test the possibilities of a more extensive use of evaporative coolers using and adobe fabric.

Acknowledgements

This and related studies have been made possible with the support of the South West Texas Junior College, especially of Don Tomas, Associate Dean of the Del Rio campus. Sid Cauthorn, President of Bank and trust, Del Rio, Texas is especially acknowledged for generous financial assistance and general support of studies of earthen building materials. Lynn Masterson, a faculty member, has rendered indispensable assistance with the software use involved with the research. Marcella Fuentes, also a faculty member, kindly reviewed and edited the manuscript. Terry Tilton, a geologist, has reviewed the study and offered sound suggestions and provide a final review of the manuscript. Lawrence Jetter, President of Advanced Earthen Construction Technologies, Inc , San Antonio, Texas has provide invaluable support in all research activities associated with earthen building materials. Thanks must also be extended to numerous former students for varied assistance in construction of the modules..

References

Kelly, R 1999. Latent Heat Storage in Building Materials, Building Services Engineering Diploma Dissertation, Dublin Institute of Technology, Bolton Street, Dublin, UK
Hewitt, Paul, 1981. Conceptual Physics, 4th edition. Little Brown and Company Inc, Boston.
Morony, John, 2005. Adobe and Latent Heat: A Critical Connection. Second Annual Conference, Adobe Association of the Southwest, Northern New Mexico Community College, El Rito, New Mexico

Something to think about on a hot Texas afternoon: John J. Morony shows how a breathable earth walls naturally cool themselves.

John J. Morony has shown how a breathable adobe or compressed earth brick building stays cooler than the outside temperature. It isn't just mass. Moisture in the adobe vaporizes, cooling it.

At the Tierra y Cal workshop on June 13, Mr. Morony, set up a simple demonstration of the effect using 4 small clay flower pots, sealed on the bottom and partially filled with water. He set up the pots in the sun and placed the saucer for each pot was placed on top of each.

After the pots had been in full sunlight for about an hour he measured the temperature of each pot and of the ambient temperature.

Ambient Temperature: 95 degrees

Pot #1 (painted on the inside with white enamel): 102 degrees
Pot #2 (painted on the outside with white enamel): 96 degrees
Pot #3 (unpainted): 83 degrees
Pot #4 (coated on the outside with naturally white lime wash) 79 degrees

John explained that any material left in the sun will be hotter than the ambient temperature, unless it breathes. Pot #2 was cooler than pot #1 because the white paint on the outside did reflect some heat energy. But because the clay walls of both pots were rendered unbreathable by the paint, they both got hotter than the ambient temperature.

The clay that made up pot #3 & 4 could still breathe. Water inside the pot and within the clay vaporized and took heat energy with it, just as we feel a chill when getting out of a pool on a hot windy day. The water vapor phase change cooled the pots and not by just a little. Pot #3 was hotter than pot #4 because the dark color of the clay of Pot #3 absorbed more heat while the breathable lime wash finish of pot #4 reflected some of the sun's heat energy.

Compressed earth block and adobe walls breathe naturally unless a vapor barrier is imposed. If the walls are allowed to breathe, the temperature of the walls will be lowest in the hottest part of the day, about 4:30 in the afternoon. Cob walls would do the same as would rammed earth, unless portland cement were used in the mix.

Photo courtesy of Tierra y Cal under Creative Commons license.

Compressed Earth Block, Lime Plaster and More Three Day Workshop in San Antonio June 11, 12 & 13

Lawrence Jetter and the AECT compressed earth block machine factory have long been a favorite field trip destination of our group. Now comes a three day workshop by Solar Adobe School and Tierra y Cal at the factory.

From adobebuilder.com:

COMPRESSED EARTH BLOCK, LIME AND MORE
June 11, 12 & 13, 2009 (Thur-Fri-Sat)
AECT Factory in San Antonio, Texas
Tierra y Cal
is pleased to invite you to participate in our
Three Day Workshop in San Antonio, Texas for Compressed Earth Block Construction, Lime Stabilization and Natural Plasters
June 11, 12, and 13, 2009
(Thu.-Fri.-Sat.) Location: AECT Factory in San Antonio, Texas

Two earth building companies and their personnel are pooling their talents to bring you this class. From Texas, Lawrence Jetter and crew of Advanced Earthen Construction Technologies bring their knowledge of pressing machinery. From San Miguel de Allende, México, Jim Hallock, Mónica Healy and Jeff Rottler of Tierra y Cal, Proyectos Sustentables, bring their knowledge of lime stabilization in combination with compressed earth block construction. Students who persevere through all of the sessions to dinner on Saturday will receive a Certificate of Completion. Class cost includes an Earth Block Construction manual.
Lawrence Jetter of AECT with one of his machines

Schedule
Thursday, June 11, 2009
8:00am - 8:15am - In the Classroom - Coffee and Introductions

8:15am - 11:45am - How to Build a Compressed Earth Block (CEB) Building - Foundation through Bond Beam. The partners of Tierra y Cal present the step-by-step sequence using the manual you will have received.

11:45am - 1:00pm - Lunch break

1:00pm - 4:45pm - Soil selection and block manufacturing with Lawrence Jetter and lime stabilization with Tierra y Cal. You will have the opportunity to press and test some blocks (bring 5 gallons of your dirt if you wish), and help to operate a pressing machine.

Friday, June 12 , 2009

San Miguel8:00am - 11:45am - Hands-on construction of a small Compressed Earth Block building. The class will learn to build a wall to the speed lead and string and construct an arch using blocks pressed on the site. We’ll place door and window bucks and set in an electrical circuit with a few plug boxes as we build the wall.

11:45am- 1:15pm - Lunch Break

1:15pm - 4:45pm - Construction continues

Saturday, June 13 , 2009

8:00am - 11:45am - We are again at AECT’s facility with a focus on lime and clay plasters.

11:45am- 1:15pm - Lunch Break

1:15pm - 3:00pm - Plaster continues

3:00pm - 4:45pm - Q and A

7:00pm - ?? - Meet for Dinner, Certificates of Completion handed out.

Class limit: 35 students
Cost: $295.00 for one person, $275.00/person for two or more registering together and providing one payment. A discount of $20.00/person will be given for early registration, prior to May 15. Refunds (minus $30.00 administration fee) will be given for cancellations prior to June 1.

This class will be conducted in English only.

The class will close when filled. Please register early to preserve your place. The first payments to clear will be registered and the attendee notified.

To register: Contact Monica Healy for the easy instructions at monicahealy@tierraycal.com

Beautiful Strawbale earth plastered demonstration building on the grouds of the US Botanical Gardens in Washington DC

Builders Without Borders has created an exhibit on the grounds of the US Botanical Garden in Washington D.C. as a showcase for natural building. In addition to the small one room structure a hardened adobe arch frames a view of the Capitol. Lime plaster, cotton roof insulation, a standing seam metal roof, a truth window and a bamboo trellis are all featured.

CHECK IT OUT- - Glorious Mud! by Gus W Van Beek. Ancient and Contemporary Earthen Design.

In "CHECK IT OUT" posts we'll spotlight books on green subjects available at our own San Antonio Public Library. First up is "Glorious Mud" by Gus W. Van Beek with Ora Van Beek. This 500 page book, profusely illustrated with black and white photos, documents the investigations of the former curator for anthropology at the National Museum of Natural History into earth built buildings the world over.

Unlike other books on natural construction this book also looks into the ancient history of earth buildings. This is not a how-to book, it is more of a survey of earth building methods and their history. It might well serve as an inspiration to a modern builder to see the multi-storied mud brick buildings of Yemen or the the rammed earth houses of Germany. To hear that the longest lasting structures of ancient Egypt were made of mud might be give confidence to someone interested in rammed earth building today. Though Mr. Van Beek suggests at one point that perhaps "adobe" would be a more attractive word to use than "mud".

Ora Van Beek, travelling with her husband, was able to gain access to the female only interior quarters in muslim countries which her husband could not, this gives a new insight into daily life in present day Pakistan and elsewhere.

The sustainable building enthusiast will find much to enjoy in this book and will come away with a much broader understanding of the many methods of using earth for building. If only the pictures were in color. Black and white photos do not do justice to the beauty of these buildings.

This book is currently in the New Books section of the Central Library. It was given to the library in honor of Library Foundation board member, Lamar Spencer. Considering the book sells on Amazon for $99.95 checking it out free from the library is quite a bargain. You can even reserve it online.

Glorious mud!; ancient and contemporary earthen design and construction in North Africa, Western Europe, the Near East, and Southwest Asia.
560 pages, Smithsonian Institution Scholarly Press (December 28, 2007)
ISBN-10: 0978846001, SBN-13: 978-0978846008

5th Annual Adobe USA Conference May 14 & 15, Provides an international education in earth building at an affordable price.

The Adobe Association of the Southwest presents Adobe USA 2009, May 14 & 15 on the campus of Northern New Mexico College in El Rito, NM, just west of Alburquerque on IH40.

Speakers at the conference include Carole Crews, one of the leading practitioners of artistic mud plastering, John J. Morony of Southwest Texas Junior College speaking on the topic of Mexican Green Roofs which was his subject at a recent San Antonio Sustainable Living meeting and Simone Swan speaking on "Hassan Fathy Father of Sustainable Architecture".

Architects, designers and builders from Nigeria, Italy, Bangladesh, France, Mexico, Ghana, the United Kingdom, Yemen, Brazil, Germany, Iran, and Portugal will be presenting at the conference.

Registration for Friday May 14 and Saturday May 15 is just $100. But pre-conference workshop courses begin May 11. These courses are offered by the Adobe Construction Department at Northern New Mexico College. Courses include: “Adobe Construction Basics”, “Arches Domes and Vaults” and “Rammed Earth Construction” taught by Eduardo Carvalho, an architect and rammed earth specialist from Portugal.

Each workshop is a two credit course. Cost per out of state credit is $87.50. Costs for New Mexico residents is $37.50. (Some additional administrative fees may apply.)

NNMC recommends completing the application for admissions and course registration process entirely online! Please visit the NNMC admissions page for more information and to begin the online registration process.

On Sunday, a local Adobe bus tour will take visitors to Taos Pueblo and the Adobe Factory. The cost for the tour has yet to be determined.