NEWS 3

Natural Lime plaster is one of the oldest of all building materials available to the builder. It has been sheltering and protecting man from the elements for over 9,000 years with the ancient people of present-day Jordan being the first in recorded history to use it as a plaster to cover walls, floors, and hearths. Thirty Five hundred years later in 4,000 B.C. the Egyptians Incorporated Lime in their buildings to include the Great Pyramids of Giza. Since then, it has found its way, as a building material, into every civilization from the Greek and Roman empires to present day civilizations in every corner of the world. With the development of artificial cements, begun early in the 19th century, the continued use of pure Lime plaster was questionable. As the Industrial Revolution unfolded, builders wanted a mortar that set fast with increased strength. These hydraulic properties were derived from lime and gave birth to the product we know today as Portland cement.

The popularization of Portland cement reversed the ages-old tradition of utilizing only pure lime. As industrial progress gained steam, people demanded that buildings go up faster and faster. However, society is increasingly paying the price for its hurry-up-and-get-it-done approach to building this way. Many structures made of non-permeable cements are cracking and failing before our Eyes.

What looms important in the present day is this critical question: does building faster, stronger, non-permeable structures create sustainable structures overall? The answer, sadly, is no.

American Indian tribes, indigenous to the southwestern portions of the United States, have long since, and today still use, a Lime based plaster to cover their earthen buildings. Made from a combination of lime, sand, clay and cactus, the plaster has very good resistance to moisture, is

semi-permeable and has the ability to expand with the changes in heat and moisture without cracking. If installed properly the plaster has a life expectancy of 100 years. Unlike the Lime plaster utilized by the people of the Middle East during ancient time and today, the plaster used in the Americas is better because of the cactus juice additive. Unfortunately, cactus is only indigenous to the Americas and does not exist anywhere else on earth. Following the age old principles and techniques long since established, UDC architects and construction personnel have been successful in adapting natural lime plaster for use in residential and commercial buildings. The results of its use are very impressive. With the introduction of the Universal home in the quest for our architects has been to find a building material that can provide both resistances to solar gain in the summer, yet still be utilized for heat storage in the winter. Experimentation with "stick" buildings (2x4 and 2x6 wall assemblies) identified problems, due to their low

R-value, to control energy costs even when passive orientation strategies and high performance insulation were incorporated into the design. The buildings still performed poorly in meeting energy performance requirements. Likewise, Insulated Concrete Forms (ICF) proved excellent as a thermal barrier; but the added cost of their use, combined with the non-sustainability aspects of the material itself (polystyrene), and their inability to "breathe," proved them to be an undesirable solution. Only with the use of compressed Earth Block (CEB) have we been able to meet both the sustainability and energy performance requirement goals. The secret to this building type is within the soil itself. Soil is negatively charged and water is a polar molecule. This causes them to attract one another. This is interesting because we know that heat is most easily exchanged though water vapor or moisture. If the earthen walls of the building have the ability to attract moisture, then we can control internal relative humidity and heat gain. As the moisture is

absorbed by the wall assembly so is heat from the building. This process is called heat flux and deals with latent heat exchange between the earth walls and internal climate of the building. This is, however, only possible if the wall assembly can change and breathe. Therefore, semi-permeable exterior and interior veneers are very important parts of this solution. The answer, as mentioned above, has been around for more than 9,000 years. It's Lime plaster. The plaster will allow this natural process to take place day to day and in turn stabilize the internal temperature of the building to around 70 degrees F. In Texas, as well as much of the southwestern part of the United States, this is very good news! A stable temperature of 70 degrees F with an observed daily and seasonal temperature flux of + or - 5 degrees will cut electrical costs of the building by 63% per year. Several experts have observed this process in greater detail working in the field. In the morning when the outside ambient temperature is low and humidity is high, the internal climate of the building is

warm with a stable with a relative humidity of around 38%. As the day heats up and the outside temperature increases and humidity dissipates, the internal building climate changes, due to the exchange of moisture, gets cooler! What is occurring is the heat being applied on the outside of the exterior wall assembly is "attracting" moisture from inside the building. As that moisture is absorbed into the Compressed Earth Block walls of the building so is the heat from the building; lowering the temperature without the use of any mechanical device. This process is repeated per solar day. For some building designs that also incorporate passive design strategies, it is possible for the building to not require any heating or cooling by mechanical devices at all. Overall, the universal homes and buildings presently being constructed have demonstrated the capability of an 85% reduction in electrical usage when the earthen wall assemblies are used in conjunction with other systems such as radiant hot water collectors, sustainability features, passive strategies, and good polar orientation. This now makes it cost effective to install a battery bank and renewable system, taking the building completely off-grid. Since 2009, all Universal series homes have been equipped with a battery storage area in the foundation to store two 1,000 Amp industrial batteries. These will allow for the integration of any of several possible renewable electricity generation systems if the home owner at any time in thefuture decides to take the home off-grid and never pay a electrical bill again.

Pictured Above: White Natural Lime plaster being installed over a 14” Compressed Earth Block (CEB) test wall at the AETC manufacturing facility in San Antonio, Texas.

Pictured Above: Nopal cactus or “prickly Pear” is a key ingredient in the production of natural Lime plaster. This cactus is widely used throughout Central and North America for its health benefits.

Pictured Above: Nopal cactus being collected and stored prior to processing for enzyme extraction.

Pictured Above: Nopal cactus being processed by HSU student volunteers in Abilene, Texas.

Pictured Above: Nopal cactus curing in a 55 gallon barrel. This will allow the enzymes to naturally leach out of the sliced leaves into the water producing a usable compound that later will be mixed with the Lime plaster to increase elasticity and durability without sacrificing semi-permeability of the CEB wall system.

Pictured Above: UDC personnel mix hydrated Lime with a hand mixer.

Pictured Above: Workers install the natural Lime plaster to a exterior wall surface. The plaster is installed in two parts; a base coat and a finish coat. The finish coat can be seen in the foreground of the picture.