Abstract
Raw earth historic and contemporary architectures are renowned for their good environmental properties of recyclability and low embodied energy along the production process. Earth massive walls are universally known to be able to regulate indoor thermal and hygroscopic conditions containing energy consumptions, creating comfortable interior spaces with a low carbon footprint. Therefore, earth buildings are de facto green buildings. As a result of this, some earthen technologies have been rediscovered and implemented to be adapted to the contemporary building production sector. Nevertheless, the diffusion of contemporary earthen architecture is decelerated by the lack of broadly accepted standards on its anti-seismic and thermal performance. Indeed, the former issue has been solved using high-tensile materials inside the walls or surface reinforcements on their sides to improve their flexural strength. The latter issue is related to the penalization of earth walls thermal behavior in current regulations, which tent to evaluate only the steady-state performance of building components, neglecting the benefit of heat storage and hygrothermal buffering effect provided by massive and porous envelopes as raw earth ones. In this paper, we show the results of a paper review concerning the hygrothermal performance of earthen materials for contemporary housing: great attention is given to the base materials which are used (inorganic soils, natural fibers, and mineral or recycled aggregates, chemical stabilizers), manufacturing procedures (when described), performed tests and final performances. Different earth techniques (adobe, cob, extruded bricks, rammed earth, compressed earth blocks, light earth) have been considered in order to highlight that earth material can act both as a conductive and insulating meterial depending on how it is implemented, adapting to several climate contests. The paper aims to summarize current progress in the improvement of thermal performance of raw earth traditional mixes, discuss the suitability of existing measurement protocols for hygroscopic and natural materials and provide guidance for further researches.
Highlights
Current methods of assessing the quality and environmental impact of contemporary built environment tend to underline the importance of energy consumption and emission of pollutants that buildings cause during their period of use
The reduction of the environmental impact of building materials and processes must be pursued from a supply chain perspective through environmentally sustainable production that is able to identify eco−efficient solutions, through the adoption of new building technologies that lead to low energy consumption and low emissions at the production, management, and end−of−life stages
Raw earth materials can be categorized in many ways, including a classification based on the manufacturing process corresponding to the different main techniques: in this paper we use this classification because mixing water content and usual soil textures for each technique have a strong influence on the final consistency of the material, distinguishing techniques which use plastic raw earth to be moulded, humid raw earth to be dynamically or statically compacted and clay slurry/slip to bond together natural fibers or mineral aggregates for insulating purposes [51,52]
Summary
Current methods of assessing the quality and environmental impact of contemporary built environment tend to underline the importance of energy consumption and emission of pollutants that buildings cause during their period of use. Over the past 30 years, many countries such as Australia, New Zealand, New Mexico, Peru, Germany, Spain, and France published several technical codes and guidelines for raw earth construction These attempts at normalization are important because, in the absence of a fully defined science of earthen construction, they provide guidelines for the design of the basic material (giving basic information about soil grading characteristics for each technique, percentage of clay in the mixtures, mixing water content), for the evaluation of its characteristics (compressive and tensile strength, percentage of shrinkage and durability properties, like absorption and erosion caused by water), as well as outlining a series of design measures useful to avoid errors or risks to the construction (maximum spans and heights of the walls, slenderness of the load−bearing elements, arrangement of openings, reinforcements, connections between perpendicular walls). This difficulty has recently led to the establishment of the RILEM technical committee TCE 274 [2] which has the mission of defining accurate, repeatable and reproducible performance-oriented testing protocols that could, in the future, be adopted as international standards
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
