Article Category: Research Paper
Published Online: May 10, 2022
Page range: 2631 - 2639
Received: Aug 07, 2020
Accepted: Nov 15, 2021
DOI: https://doi.org/10.2478/otmcj-2022-0007
Keywords
© 2022 Žiga Turk et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.
The creation of digital twins – both of the building products and the building process – has become the usual way of designing and planning buildings. The building information modelling (BIM) technology is replacing earlier ways of representing designs (e.g., drawings and maquettes) and plans (e.g., Pert Charts and the like). Standards (e.g., Industry Foundation Classes (IFC)) and software packages (e.g., Revit or ArchiCAD) invite the parties involved to create digital replicas of the building product in question in high quality. This is very different from the communication of designs on paper or as maquettes, where the difficulty of creating them and the abstract level of communication standards directed the participants towards a messaging model of communication and information exchange. This communication included only information needed by the recipient of the information and not necessarily the information that would represent the facility to be (re)built.
In this paper, we aim to restore the original role of information, designs and plans – which is primarily for information and not for representation. We will propose to create a process-model that is as simple as possible, resulting in a product model. The work presented builds on the initial ideas of Turk et al. (2019). The approach will adopt the idea of structured information based on standard building blocks from the BIM approach, drawing from the experience of the Horizon 2020 Intelligent Services for Energy-Efficient Design and Life Cycle Simulation (ISES) project (Katranuschkov et al. 2015), however, focusing on the parsimonious nature of information – as simple as possible – from the tradition of design communication in engineering and construction.
The approach will be applied in an area where such a lean approach makes sense – the energy retrofit of existing buildings. It is a relatively simple process, carried out by SMEs (Small and Medium Enterprises), which may be relatively under-equipped but can still benefit from the availability of better information.
The rest of this section provides the motivation for the work (Section 1.2) and states the research objective (Section 1.3). It is followed by a review of related work, both one's own and that of others (Section 2). Then the components of a generic parsimonious process model for energy-efficient renovation and the model itself are presented (Section 3). The paper ends with conclusions and discussion (Section 4).
Up to 40% of primary energy is consumed in buildings. They contribute significantly to the CO2 emissions that result in global warming. This is similar all over the world. The life span of buildings is measured in decades, sometimes centuries. We cannot hope that new and more energy-efficient buildings will be built to replace the inefficient old ones. They are not like cars or electrical appliances – where the next generation can be more energy efficient than the previous one.
In China, Europe and elsewhere, there has been a serious housing crisis following the baby boom years after the Second World War. The crisis was addressed by the rapid construction of high-rise apartments. They were built economically by copying the same design many times, and this at a time when energy was cheap. Many such buildings can be seen on the outskirts of all major European and Chinese cities.
The problem with these buildings today is that they are not only not very energy efficient, they are also unattractive and grey relics of a certain past age. The only realistic way to improve the energy efficiency of the buildings is through renovation. This is a goal of many national strategies, including those of China and Slovenia (Government of Slovenia, 2019).
Since climate change issues have moved to the fore-front of policy, major renovation programmes have begun around the world. The main aim is to improve the façade, both in terms of energy and aesthetics.
The aim of this work is to investigate how the essence of the BIM approach (consistent, structured, standardised, reusable information) could be used in cases where the facility in question is not being rebuilt, where only a small subset of information about the building is actually needed and where the associated process is repetitive. One such issue is the energy renovation of buildings: only a small amount of information about the building is needed, there are several identical or similar buildings, the processes are repetitive and there are low-tech SMEs involved.
The specific tasks of this work include as follows:
Reviewing how the BIM technological approach is used for renovation, especially for renovations with a focus on energy efficiency. Analysis of the renovation process and its information needs. We examine how the process is carried out, what its knowledge is, what information is needed in the process and its sub-processes, and to what extent the process can be reused from one construction site to another. On a sufficiently high level of abstraction, all these processes are the same, which allows for repeatability even in the construction industry, which is otherwise known for its unique buildings, which are built in one-of-a-kind construction processes. This is very different from other industries where mass production is the usual method of production. Develop a parsimonious subset of the building process and product model and do not strive for the most realistic and complete building information model possible. Modelling requires effort, and information modelling is no exception. It must be economical just like any other process. All information generated must be justified by the needs in the downstream processes. Although we do not strive for a realistic BIM model, we are investigating how ISO standards (ISO, 2018a; ISO, 2018b) and the OpenBIM approach (
Renovation processes have been a topic of research of several research teams (Section 2.1) and have been addressed by the earlier work of the authors of this paper (Section 2.2).
Within the TES project (Cronhjort et al., 2009), the renovation process was divided into the following phases: building examination – digital measurement – planning – off-site fabrication – on-site assembly. This approach used prefabricated elements for fixing to whole or large façade surfaces, which required a fairly detailed model of the building's exterior. The project was implicitly aware of the compromise between BIM complexity and renovation requirements.
In renovation projects, BIM technology was seen as a welcome tool. Yin (2010) claimed that it plays an important role in energy and cost savings over the life of the buildings, especially in the building management phase – it allows simulations in the digital twin of the building.
Di Mascio and Wang (2013) claimed that BIM in particular makes the design, organisation and construction of renovation projects manageable and even improves them. They see advantages in three dimensions of sustainability, environmental impact, and economic and social benefits.
Aldanondo et al. (2014) dealt with the problem of the industrialisation of energy renovation of apartment buildings. This particular problem limits the need for BIM information to the external dimensions of the building and also sees the need to project some structural features of the building onto the outer shell. The paper (ibid.) presents an implicit ontology that is useful as a starting point for our work. It defines a renovation process that comprises five phases: building geometry generation, building analysis requirements characteristics, renovation-specific design, manufacturing of pre-made components and renovation on the building site. It differs from our work in that it deals with prefabricated elements for improving the building's characteristics.
Hammond et al. (2014) examined the use of BIM in retrofitting and renovation by professionals and the implications for their practice. The authors examined a renovation process that aimed to use BIM ‘in as many areas as possible’ in order to comply with the LEED (Leadership in Energy and Environmental Design) rating system. One of their findings was that the functions of BIM information exchange and collaboration made it a great tool for the renovation of existing buildings, regardless of the scope of the renovation. Benefits were also identified in energy simulation and conflict resolution. It can be assumed that a rather thin BIM model will be sufficient, but the work did not focus on establishing a standard model or process.
Khaddaj and Srour (2016) defined a renovation process with three stages: pre-energy modelling stage, energy modelling stage and refurbishment options stage. They identified the challenges related to the use of BIM for renovation purposes: the multidisciplinary nature of the participants, the timeliness of the exchange and the wide range of technologies. In the research agenda they pointed out that both the Information Delivery Manual (IDM) and the Model View Definition (MVD) focus on new buildings rather than existing ones. Construction Operations Building information exchange (COBie) standard does not include architectural and structural components that could be relevant to renovation. They concluded that ‘BIM is still immature for its full adoption in refurbishment projects because of technical, informational and organizational complications’. Our parsimonious approach should address these complications.
Scherer and Katranuschkov (2018) coined the term ‘BIMification’ for a process in which BIM technology is used extensively in the design and implementation of renovation processes. They proposed a structured approach for the creation of a BIM model of existing buildings to be used in retrofitting. The renovation process is divided into anamnesis (collection of data about the building), diagnosis (analysis and interpretation of the collected data) and therapy (design and implementation of the retrofit). As this is a generic approach, it results in a rather complex, thick BIM model, which in our opinion contains more data than required for our class of building
The topics were investigated in the ISES project, an H2020 project from the EU FP7, which was running from 2011 to 2014. ISES developed ICT (Information and Communication Technology) building blocks to integrate and complement existing tools for design and operational management into a Virtual Energy Lab able to evaluate, simulate and optimise the energy efficiency of products and facilities, especially components for buildings and facilities, before their realisation and taking into account their stochastic life-cycle nature.
The ISES Virtual Energy Lab (see Figure 1) was principally structured into four main tiers as well as two supporting tiers (Baumgärtel et al., 2013):
The first tier (Figure 1, from left to right) is the domain modelling and input tier to the VEL. All of the domains and inputs are to be combined to one model and configured appropriately to the various approximated stochastic simulation input models. The procedure has to be automated with the support of the tools of the second tier to provide the necessary efficiency. The second tier is responsible for the configuration of the various simulation models, reducing manual labour. This is achieved with the help of the multi-model combiner that combines the different domain models to one investigation model. The objective is to configure concurrently as many as possible simulation models in order to reduce sequential simulation and hence the overall simulation time to a usable scale for AEC (Architecture, Engineering, Construction)/facility managers' (FM) practice. Since the processes on the first and second tiers have to be repeated continuously for each design cycle, a number of simulations may be necessary to obtain an energy- and emission-efficient design solution. This cannot be carried out on a reasonable scale on a single workstation, therefore access tools for cloud computing are allocated on a third tier to provide the needed computing power. The fourth tier is dedicated to services and tools concerning the evaluation of multi-models, including the prioritisation of the results and supporting services.
Fig. 1
ISES Virtual Energy Lab architecture (Katranuschkov et al., 2015).
One of the results of the project was an energy-conscious decision-making process that started early in the design phase and had a strong impact on the costs and energy performance of the building being validated. The workflow was supported by powerful cloud-based services using pre- and post-processing tools. The workflow was consolidated along with all required services into an extensible open-source virtual laboratory kernel.
Nevertheless, the project showed that there are many challenges in performing design analysis. While some of them are much less serious today than in 2014 (such as the lack of BIM experts or missing BIM and other relevant standards at the national and global levels), there are still issues to be resolved. Many of them have to do with the nature of BIM and what BIM actually is to a project group. The ISES project has shown that not all BIM models can be used for every analysis and at every stage of the project/project design. While there were parts of the model that were usually not detailed enough (such as HVAC (Heating, Ventilation, and Air Conditioning), which usually lacked important attributes), the models were mostly too detailed, which made the analyses more complicated and led to non-converging computational fluid dynamics (CFD) equations, time-consuming processes and unusable results.
The ISES project has shown that there is a need for a reusable BIM solution for repetitive project tasks, one of the most important being the transition from architectural to (simplified) energy simulation-specific model views.
First studies on the process and information analysis have been carried out in several master theses at the University of Ljubljana. On one side of the spectrum is the work of Todorović (2009), who created a detailed BIM model for the renovation of a building. On the other side, Radošević (2015) researched a simplified SketchUp geometry of the building, which would be sufficient for estimating insulation, shading and energy requirements. The quantity and cost estimate for a given building was created using software from a specific insulation manufacturer. This software is not a general-purpose BIM modeller but a specialised software that lacks several features of BIM. However, its information needs are a very good example of what information is actually needed for a renovation using a particular technology. Stamač (2017) carried out the renovation of a typical building, which was the aim of this project, and its analysis showed that a rather limited set of data is needed for the analysis. This work also provides a good context for the analysis of information needs.
We use the IDEF0 (“Integrated computer aided manufacturing DEFinition for Function modeling”) notation, which distinguishes between inputs, outputs, controls and mechanisms. In this section, we first describe the technological (3.1) and human mechanisms (3.2) as well as the controls (3.3). Then we introduce the parsimonious renovation process model (3.4), which forms the basis for the forthcoming product model.
Several families of information technology are used in renovation projects. The list of technology – listed roughly in the order in which they come handy – include as follows:
Actors may differ slightly given the business model of renovation, ownership status, size, and technical difficulty of the renovation and include the following:
Owners. The building to be renovated may be under different ownership regimes. Typical in Slovenia and many other south-European countries would be a case where owners and tenants are the same people living under the roof they own. There are also cases where tenants are renting the apartments owned by others. Entire buildings owned by private owners or the local community that are renting the buildings to tenants would be an exception. Tenants. People who live in the building to be renovated. Typically, there would be a large overlap with the tenants (as explained above). The relation between owners, tenants and heating providers may determine the business model of the renovation but less so the technical process of renovation that we are studying. Heat providers may be third parties (like for distant heating) or the heat provider could be organised for the building as a whole or (exceptionally) for individual apartments. Again, the differences mostly affect the business model. FM. In Slovenia, each building with multiple occupancies beyond a certain size needs to have a facility manager that is in charge of building maintenance and distribution of costs related to the building including, but not limited to heating and cooling. Local authorities. The competent authority where the building is located such as municipality or state. It could have programmes and incentives in place for building renovation. Renovation designers. The company that designs the renovation. Renovation contractors. The company that performs the renovation. Renovation subcontractors. The subcontractor to the contractor.
In the context of the understanding of building processes – so that the information processes control the material processes – the controls of the renovation processes include the following:
Building codes. Funding and incentive schemes. Criteria and limitations. Design documents. Permits.
We examined the documentation of existing renovation projects, their information needs for analysis and the design and renovation process, and spoke with practitioners in the renovation industry, particularly in relation to design and renovation decision making. The aim was to create a generic, parsimonious process model that would serve as a guide for industrialised construction. The renovation process presented in Figure 2 is therefore a combined result of the above-mentioned research, limitations of local regulations in both Europe and China, and the experiences of the professionals from the renovation industry. Although the process is not definite or prescriptive in terms of methods and steps, we believe that its generality makes it widely applicable.
Fig. 2
The generic renovation process in IDEF0 notation.
The process is shown in Figure 2. The figure uses the IDEF0 notation. Rectangles are processes. Black arrows entering the process from the left are inputs and those exiting from the right are outputs. From above, the process is controlled by information or actors. From below, the processes are supported by actors and technologies.
The process begins with the identification of needs. It is based on information about the energy consumption of the building when compared with the energy consumption of other buildings, and the general condition of the façade. Aesthetic reasons are often an essential element in the decision to renovate. The determination of needs is controlled by the owner, the tenants and the FM. The result of the needs assessment is a rough calculation of the profitability of the renovation – a rough estimate of the costs.
Then the business case for the renovation is drawn up – taking into account all the incentives available from the government and heating providers. This is something that the owners must control and the authorities and heat suppliers must support. The results are design criteria and constraints – in particular what the improvements in the energy performance of the building would be and whether or not the renovation of the windows and roof structure is part of the renovation.
The design process for the renovation takes the information about the existing building as input and the design criteria and constraints as control. The result is the renovation design. In its simplest form it would include the material and thickness of what would be glued to the façade (rock wool, polystyrene, etc.). It may also contain information on how to solve certain repetitive details around openings and balconies. BIM and other technologies listed in Section 3.1 can also be used. In typical buildings, this would be sufficient for the renovator to do the work.
The building is being renovated. Existing buildings and raw materials enter the process and the renovated building leaves the process. The process is carried out according to the design specification, relying on construction technology, contractors and subcontractors.
Finally, the building is handed over to the owners and tenants.
The two most important information elements in this process are the information on the economics of the renovation and the renovation design. This information will be further examined in the follow-up work. The aim is to define information structures that are as simple as possible and sufficient for carrying out renovation work.
To validate the concept of the proposed parsimonious renovation process and its applicability in practical user scenarios, it was tested on a use case (sample building) from the ISES project and compared with the generalised workflow of the ISES-VEL platform (Figure 3). Although the ISES project included two use-case buildings, only one of them was suitable for our model, since the other one was newly built.
Fig. 3
ISES use-cases used for the validation of the proposed parsimonious process (Leskovšek et al., 2014).
The use-case construction project dealt with the refurbishment of a historically important auxiliary building for the renovation/conversion process. The building had a regular square footprint, a basement, three above-ground floors and an attic. One of the most important requirements was to preserve the façade, and the renovation resulted in extensive changes to the interior. In order to analyse the effects of the renovation, two models of the building had to be created: one for the structure before and one for the situation after the renovation (Katranuschkov et al., 2015).
We found that the ISES workflow in our model is a superset of the parsimonious process. The first three activities of the parsimonious model (Figure 2) correspond to the developed ISES VEL workflow (Figure 1). Demand assessment corresponds well to the use of energy-related Key Performance Indicators (eKPIs), which also served as benchmarks to evaluate and quantify different design decisions. Relevant eKPIs were also used to consider the relevant economic indicators for the life cycle of the building and its components, which define the business case for design criteria and constraints that influence the decisions and consequently the final design. The proposed process ends with the renovation work and handover as the final step in the workflow.
We have presented the motivation, objectives, points of departure and first results of a Chinese–Slovenian project that aims to enable an industrialised renovation of residential buildings with BIM concepts and technology. We chose the BIM approach – the use of open, standardised, structured, object-oriented information in a collaborative environment – but have not adopted the ambition to create information models that contain as much information about the building as possible. Rather, the goal was to find a subset that is as simple as possible and good enough. A literature study and earlier work show that the need for information in an energy-efficient renovation is quite different from that in a new building, as is the process itself.
We have presented the components of the renovation process, which includes the actors involved, the technologies used and the regulations to be taken into account. Based on these, we outlined a typical renovation process in which the elements just listed control or facilitate the sub-processes. We have identified the two most important information elements – the economics of renovation and the renovation design.
Further work in the project will focus on the details of the information structures of the renovation economy and renovation design. First results and experiences from the industry show that much less than a complete building information model is needed – not even a 3D BIM model of the exterior of the building is inevitable. What is needed, however, are the areas to be covered and, more importantly, typical and repetitive details. How this information can be structured, organised and shared is a topic for the next phase of the project.