In a second time, the AEC firms interviewed are analysed as groups  rather than as individuals to identify current practice and determine trends,  as shown in Figure \ref{248888}. Therefore, all design practice are gathered together in  relation to their dimension, creating two synthetic graphs: one for the  medium-size firms and one for the big-size firms. Despite the previous graphs  developed at individual level, the cumulative graphs picked out only the most  significant indicators, respectively “structure”, “experts”, “topics” and  “tools”, with the aim to briefly illustrate the difference inherent design  firms according to their size. Here the focus is on the technical-operational  area that it is in turn divided in sub-specialized units to meet the emerging  issues, such as energy and environment, systems, quality, safety and ICT, just  to mention a few. Every unit is made up of individual experts within  medium-size firms, while is built of specific teams within big-size firms. Of  course, not all the specialized units with the related experts and specialists  are embedded in all the analysed design structures, but their existence shows  the growing interest to the performed issues and their strengthening over time to  the point to require their establishment within the firm. When  for economic and/or organizational reasons not all the required different  skills are present internally, AEC firms rely on external partners to meet the  specific design requirements. For medium-size firms this happens quite often,  especially if they deal only with architecture or engineering, but also for the  integrated practice. Nevertheless, even big-size firms, although they embedded  all the expertise in house and they are technically able to handle all the  aspects of the project, sometimes they prefer to be supported by external strategic  partners that know local requirements and have better skills in certain area to  enhance the project. Environmental issues are generally addressed by AEC firms  and are stressed in different manner within the design process. Here the mindset  of the client and the type of project play a key role in fostering the  greenness that, as shown by questionnaire’s feedback, have focused on energy  and water for the past 5 years and on health and wellness starting from 2016  and beyond. Big-size firms usually comply with all the aspects related to  environmental and human impacts, while medium-size firms mainly deal with  energy issues, since it is the subject that raises more interest in clients and  customers. Concerning the tools used, all the AEC firms interviewed claim to be  BIM-oriented in order to facilitate the exchange of design data but also to  make verifications with other software, including simulation plug-ins as well  as stand-alone modelling software. Indeed, nowadays, every design company is  accustomed to make simulations to analyze the performance of the project, choosing  from a wide range of tools able to meet every design demand from energy and  lighting simulation to impact assessment and so on. In this case, while  generally medium-size firms used the tools available on the market, big-size  firms developed some of them in-house to customized their equipment to specific  needs. On the contrary, the minority of the firms interviewed, involving notably  the big-size firms, use to attach in the BIM model the environmental  information of the products, including external LCA database rather than  personal data. Concerning LCA analysis, 44% of the firms interviewed are used  to develop LCA studies of the projects/services, involving specifically the big-size  firms in all the type: architectural, engineering and construction companies. They  adopt the LCA tools available on the market (for instance SimaPro for  construction company and Tally in implementation within integrated practice) and  the connected environmental database embedded. Typically, LCA is performed starting  with the technological components accountable for the large impacts, such as  concrete, steel and façade, and then working down to the  smaller installation items. By contrast, the resulting 56% of company, engaging  in particular the medium-size firms, do not perform LCA analysis essentially  because it is not required by clients and regulations. Nevertheless, sometimes  they estimate the environmental impacts of the projects (expressed in tCO2e/y),  considering only the in-use phase and so the energy consumption. However, all  the companies surveyed are aware that LCA becomes part of many Green Building  Rating Systems and so that they probably should implement it within practice,  if they do not want to rely on external consultants focused on life cycle  services.