# Retrofitting a Building's Envelope: Sustainability Performance of ETICS with ICB or EPS
## 2 State of The Art: Life Cycle Assessment (LCA) Studies of Buildings' Envelope  
LCA studies of building envelope alternatives have been gaining momentum in the construction industry in several countries to help the assessment of solutions to improve the overall performance of the buildings envelope. This envelope is one of the most important parts of the building in terms of its 3E performance. For example, the external walls have a direct influence in that performance due to their large contribution to the envelope's whole-life cost, users comfort, initial embodied energy, and life-cycle energy consumption. The 3E impacts of an external wall solution directly result from the properties of the materials used (e.g., thermal properties, initial embodied energy, and design and construction process). Therefore, in the design of new construction or refurbishment alternatives for building envelopes, it is very important to have a method that enables the comparison of different solutions and determines the best solution to implement in each case. In several countries, there are ongoing studies to help the development of these methods, and some of their applications are to determine the solutions that have the best performance when used in the buildings' envelope, such as the following ones:  
* The LCA of a house in Portugal was calculated considering seven alternative solutions with similar thermal performance for exterior wall, and seven different heating systems. This study included the production stage and the maintenance requirements and the heating energy for 50 years [7]. In the same country, two alternative external claddings (rendering and stone cladding) were compared in an interdisciplinary study of service life prediction and environmental LCA [8]. * In China, for an office building, five facade solutions were compared considering their economic cost, life-cycle environmental load and cost, and operational energy. Green and general payback times were also calculated [9; 10]. * In the United States of America, 12 external wall solutions were studied in terms of embodied energy and thermal performance in a building at a cold climate region [11]. * In Australia, a study was undertaken to demonstrate the need to consider not only the life-cycle energy of the building but also that due to activities undertaken by actual users of the building, which comprise: Embodied energy in the production of building materials, building's operational energy, and consumption of energy in periodic maintenance over a 30-year study period [12]. * In India, the energy consumption demands of a residential building were evaluated considering different climates and envelopes (fired clay, concrete blocks, soil cement, fly ash, and aerated concrete) in the context of that country [13]. * In the United Kingdom, a LCA from cradle to site of a low-energy house built using an offsite modular panels timber frame system was used to assess the emissions from materials used in construction, final transportation of the materials to site, wastage of materials on site, transportation of waste to final disposal, and nonrenewable energy used on site using the external thermal envelope as the comparison unit [14]. * In Spain, a study was made, using LCA performance over an 80-year study period, for evaluating the environmental impacts of five constructive systems for the envelope of a modular house with conventional brick, conventional brick only with polyurethane insulation and also with Phase Changing Materials (PCM), hollow brick, and hollow brick with PCM [15]. * In Italy, for a conventional house and office building, envelope solutions (with different type and width of masonry and insulating materials), facilities (heating boiler replacement), and smart systems (namely active- and passive-solar systems) were considered in the LCA performance to determine the best solution that could be applied in the construction [16].