نقشه برداری و جریان کاری دیجیتال در پروژه های مقاوم سازی عملکرد انرژی با استفاده از عناصر پیش ساخته

Due to the need for improving the energy efficiency of existing buildings, various methods for energy retrofitting are being developed. One such initiative is the TES Energy Façade project, a joint European academia and industry project under the umbrella of the WoodWisdom Net research platform. The project has developed a systematic approach for using prefabricated timber-framed elements that can be assembled in front of an existing façade. The TES approach requires a detailed and precise documentation of the as-built/as-maintained conditions of the existing façade. This paper discusses the approach for the surveying and documentation of a building's existing state and the need to establish a continuous digital chain that encompasses the various project stages from the survey to the site assembly of the elements. Technologies such as 3D laser scanning and BIM are efficient tools in the process but are not yet sufficiently developed to handle all of the challenges in renewal and retrofit projects.

The improvement of the overall energy performance of existing buildings is currently a key component in the national energy efficiency policies because existing buildings are responsible for 40% of the energy consumption in the EU and US[1]. The residential sector accounts for the largest portion of the building sector energy use. Insulation retrofitting is one of the key strategies for conserving energy in existing buildings. The need for insulation is found in all of the main envelope constructions of a building, particularly in the external walls and roofs. Better insulation also reduces thermal bridges and provides proper air tightening, and thus reduces the energy loss as well as the heating and cooling costs. The manufacturers of insulation material have developed various systems for insulation retrofits based on their products. The TES Energy Façade (2008–2010) research project addressed the insulation retrofit problem by studying the use of prefabricated, customized, timber-based elements mounted on existing external walls and roofs[2]. The prefabricated elements consist of a timber frame as a load bearing structure that contains the insulation, wind and moisture barriers, external and internal cladding and pre-assembled doors and windows. The elements are transported from the factory to the building site and mounted in front of the existing building envelope. Fig. 1 shows the TES process from the measurement to the mounting of the elements. Fig. 2, Fig. 3 and Fig. 4 show the prefabrication, the completed elements and the mounting.Because the prefabricated timber-based elements are produced with strict tolerance requirements (typically ± 5 mm), a major challenge for the TES method is adapting the prefabricated elements to the geometry of the existing structure. Outfitting an existing object with new, industrially-manufactured components in the TES method is related to challenges in many other industries that work with reverse engineering (RE). The process of RE is described by Abella et al. [3] as the basic concept of producing a part based on an original or physical model without the use of an engineering drawing. Therefore, the methods for documentation of the as-built/as-maintained conditions of an existing structure are a major challenge for the TES method. Additionally, the project also addressed how the data from the documentation and surveying in the initial phase of a project could be reused throughout the project from the design via fabrication to the final mounting of the prefabricated elements on-site. This paper focuses on the portion of the TES project that deals with the survey and digital workflow.

Considering the importance of energy performance retrofits of existing buildings in the agenda of regional and national policies and the size of this market, it is obvious that retrofit projects, in the years to come, will be a major challenge for the building industry. Additionally, the prefabrication approach has multiple advantages as a sustainable building solution. The general advantages of prefabrication are also applicable to the TES method. These advantages include the following [22]: • A high quality due to the construction work of the elements being performed in the controlled environment of a factory. • Less waste because less adaption and adjustment is necessary. • The waste generated in the prefabrication plant can be recycled. • Lower erection costs on-site. • Minimized construction work on-site. • No construction moisture during the erection process. Although the actual fabrication of the elements and assembly on-site is efficient and quick, some challenges remain during the documentation and planning stages of the TES process to streamline the method and make it more cost-effective. As discussed in this paper, these challenges are listed, as follows: (1) the efficient and automated documentation of the as-built/as-maintained condition of the existing buildings; (2) the extended use of BIM technologies during the planning stage, the creation of a continuous digital chain from the initial documentation to the on-site phase and subsequent management of the retrofitted building. Thus, the requirements for further development are related to automation in the post processing of data from 3D laser scanning and innovative developments in the use of BIM tools for the renovation and retrofitting of existing buildings. High-precision remote sensing provides cost-efficient methods for surveying the building stock. The acquired data is of a good quality and can be used in prefabrication. Consequently, the level of detail and the significant coordinates must be identified both by the surveyor and the customer. The general lack of 3D planning methods and BIM in architectural offices, especially in retrofitting projects, has hindered a continuous digital workflow. To obtain an adequate cost–benefit ratio, consulting from a surveyor is necessary. Cost control can also be accomplished by the stepwise use of appropriate surveying methods. Digital technology allows for this approach and guarantees consistency. There is also hybrid survey hardware on the market, the so-called intelligent total station, which integrates the previously described measurement methods into one solution. A user-required specification is required to define the content, the level of detail and a description of the 3D model. The increasing use of 3D methods in the planning stage is a precondition for retrofitting projects to reduce costs and avoid errors. Furthermore, the use of the BIM tools in retrofit projects requires a deeper examination, and their capabilities should be enhanced on the survey side. There are large requirements in terms of the tolerances and content to prepare useful surveying results for a TES EnergyFaçade retrofit. As a consequence, post processing the survey data into an abstract 3D wireframe is a costly and responsible task. The surveyor has a large amount of responsibility for this task and requires additional knowledge in construction and close cooperation with the client. In summary, the conclusions demonstrate that modern surveying methods combined with reverse engineering methods are necessary for retrofit projects. They can optimize the workflow, enhance the robustness of the TES method and facilitate the application of prefabrication to retrofit projects.