Environmental impact assessment of vernacular thatch building tradition in Mexico: Case studies of three palm species and related technology along the Trans-Mexican Volcanic Belt

This project involves research into vernacular buildings, in particular traditional and contemporary coastal palm thatch buildings in the middle-west coast deciduous forest environments in Mexico. The fieldwork-based grounded theory research investigates the natural materials and techniques involved in constructing thatched vernacular buildings using three different palm species (Attalea guacuyule, Brahea dulcis and Sabal rosei) in different climatic contexts along the Trans Mexican Volcanic Belt (TMVB). The aim is to achieve a holistic approach to the environmental assessment of these building types through a life-cycle assessment.  The present research emerges from the premise that vernacular buildings are generally taken for granted as sustainable, and yet they are under-investigated meaning this assumption may not be correct. In general the performance of vernacular buildings in terms of sustainability and in relation to their embodied energy is under reported, particularly in terms of vernacular case studies in Mexico. However the deterioration of the environments where such buildings are located through anthropogenic causes is of world-wide importance, therefore it is a priority for this research to study the relationship of the vernacular traditions with their immediate environment.  The first section of the thesis analyses theoretical frameworks for sustainability and vernacular architecture. Both terms are widely used and carry many different meanings, so it is important to establish the definitions used in this research to better set the boundaries of the study as a basis for seeking the best methods for assessing the environmental impact of the selected vernacular thatch building technologies.  The second section undertakes qualitative and quantitative fieldwork on traditional practices of palm thatch buildings in selected regions of Mexico and related case studies, six in total. The fieldwork was combined with investigation into ethnographical, ethnobotanical and historical records and data for the three palms used for thatching and their related materials and technologies in order to derive data concerning yield factors, lifespan of the building materials, carrying capacities, embodied energy of transport and embodied energy of materials.  The third section applies the collected information for a life-cycle environmental assessment (LCA) of two typical buildings for each of the three different palm species and the diverse techniques involved. The assessment is carried out based on various assumptions that are commonly used in LCA to give a carbon account and an ecological footprint for each building component both after construction and for a 50 year building life.  However, during the research particular variables in the analysis were revealed, such as operating energy, recycling of building elements, durability of materials and transport practices, which can vary widely from case to case, therefore the limits and scope of the assessment excluded such data for a better comparative scenario of the building process itself. This suggests that a different way of life-cycle accounting may be needed when assessing vernacular structures.  The results show the environmental impact of these techniques in terms of carbon and ecological footprints, and reveal that the rural vernacular case studies had lower environmental impacts than the suburban and urban vernacular case studies as measured by their carbon content, energy expressed in Giga Joules (GJ) and their ecological footprints.