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A key barrier in building-facade renovation processes is that, contrary to new designs, an initial building model where the design process is based rarely exists, and the technologies usually employed to create it (e.g., based on point cloud scanning) are costly or require modeling skills. This situation is a clear limitation, especially in early decision stages, where the level of detail required is not very high, and the analysis and studies to consider the renovation plan (e.g., simplified energy simulations and renovation potential, or estimation of the number, types, and dimensions of the prefabricated modules incorporating solar panels) highly depend on such digital models. This paper introduces a process that, based on freely available data such as open GIS sources (local Cadasters, OpenStreetMap…) and façade images, can semi-automatically generate the 3D building model of the existing conditions, and in a second step also suggests the prefabricated facades module layout for building upgrades. Additionally, no onsite visit is needed. When the upgrade is focused on the façade, a big opportunity is identified for generating the building model and a realistic representation of its envelope, only using online data sources as input. The process developed consists of a set of easy-to-use software tools that can be used independently or combined in a workflow, depending on the available data and starting conditions. Time saving is very clear and costs can be reduced.

The challenges of achieving the 2020 goals in terms of energy savings and improving efficiency are guiding numerous research initiatives looking for more insulated envelopes, dealing with thermal performance of insulation materials and envelope systems. Nevertheless, the envelope integrates within the building and this improvement on the insulation performance has to be properly adopted, taking into account the interrelation of main elements composing the overall system (facade, frame, slabs, openings, partitions etc.), as well as side effects originated not only for new erected buildings, but specifically in renovation and retrofitting works. This paper describes real experiences when considering various options for upgrading the facade through the increase of the insulation capacity, starting from external overcladding prefabricated panels and ventilated facades, advancing to more sustainable low carbon systems and ending with even more highly insulated solutions employing aerogels. Lessons from these cases, where energy and hygrothermal assessments have being carried out, demonstrate the influence of the design and construction phases and the relevance of disregarded effects such as minor thermal bridges, uncontrolled craftsmanship on site, and moisture transfer for the different technologies considered. Finally, possible alternatives are provided to overcome some of the detected difficulties, such as combination with non-metallic structural components and building membranes, and being prepared for future challenges and new developments when these isolative elements are combined with other technologies, as for example, renewable energy harvesting devices.