Análise ambiental de alvenarias em blocos: uma discussão baseada na avaliação do ciclo de vida e no desempenho térmico de envoltórias

Abstract

Selecting construction materials that minimize environmental impact is a strategy that contributes to the eco-efficiency of a building. The life cycle analysis (LCA) stands out as a method that aids the choice of products from an environmental perspective. This tool allows the measurement and evaluation of products' environmental impacts within predetermined limits and according to the functional unit. Frequently, in studies of construction materials by means of LCA, products are analyzed exclusively by the main function intended (structure, building envelope, roof). However, the environmental analysis of a single material or construction in a building system may lead to erroneous conclusions by limiting to inventory and evaluate only the primary stages of the cycle (resource acquisition, manufacturing and transportation), disregarding their behavior in operation stage. One way to examine this aspect is to consider as a functional unit of LCA study, not only the material but a building envelope that provides a predetermined thermal comfort. Given this scenario, this work proposes an environmental analysis of envelopes for a single family house, composed of concrete blocks or ceramic brick walls, with similar thermal performances. To achieve this goal, an evaluation of thermal performance of external walls of the reference house was carried out, and for the determination of envelopes with similar thermal behaviors it is considered that the thermal resistance would be sufficient to describe the thermal performance. The LCA software package SimaPro 7.1.8 was used to understand the environmental impact. For the analysis disregarding the thermal performance of the walls, the results indicate that the life cycles of the envelopes carried out with ceramic blocks cause more environmental damage in the primary stages compared to the same phases of the cycles of the envelopes in concrete blocks. However when considering the operation stage in envelope impact evalutation, concrete houses would require increased energy consumption if the users requested refrigeration or heating to achieve better thermal comfort. Simulations comparing the life cycles of envelopes composed by blocks of different natures and similar thermal performances indicate that the concrete block walls have greater impact to the environment in all groups of damage: human health, ecosystem and resources.