Considering that 35% of the buildings in the EU are over 50 years old, the renovation of buildings represents a substantial potential for energy savings. The EU estimates that improvements in the energy efficiency of buildings could lead to a reduction of energy consumption in the order of 5 - 6% and a reduction of CO2 emissions of 5% (European Commission, 2019). Building energy performance is the basis to make any decision to enhance the energy efficiency of a building. Unfortunately, building energy performance models are rarely used in building design, commission and operation. The process is very time consuming, costly and labor int ensive. Furthermore, the delivery of the results takes too long. Within our approach, we present a method how to build energy models only by changing elements of existing building energy models. This paper presents an energy simulation approach that allows designers to evaluate the performance of a combination of different energy savings products that are available on the market
According to Buildings Performance Institute Europe , 40% of the energy consumed and 36% of CO2
emissions in the European Union are related to buildings
Renovation strategies are required to find existing energy saving products that can be installed to
achieve energy efficient renovation. The energy use of buildings depends to a significant extent on
how the various elements of a building work together as systems, rather than depending on
efficiencies of the individual devices
Unfortunately, building energy performance models are rarely used in building design, commission
and operation. The process is very time consuming, costly and labor intensive. Furthermore, the
delivery of the results takes too long. Also, the quantitative results are difficult to reproduce or to
compare to each other
In our approach, we want to present a method how to build energy models by changing elements of
the buildingmodel. Based on Building Energy Models fromreal construction projects, we wantto show
the energetic effects by changing the elements for renovationwithin the model. As input variables, we
use weather conditions, building description and building component descriptions. The inputs for
component descriptioninclude the elements of the building,for example façade elements or windows.
Within our approach, we take these building elements as the basis for the simulation. The
improvement of the building elements has the advantage of being simple to model. Moreover, it
provides important information to support development of energy efficiency buildings or to justify
investments
We want to show a proceeding to simulate the whole building energy changes based on different design strategies. To overcome the uncertainties with re spect to building renovation, this paper presents an energy simulation approach that allows designers to evaluate the performance of a combination of different energy savings products that are available on the market. We do the energetic simulation with the help of EnergyPlus. This software simulates almost all types of buildingswiththere elements. In addition to that, EnergyPlusruns building energy simulations based on their components. The Building Energy Data will come from real demonstration cases, which are in three different countries in European Communion. We will start with three Energy Models to test our approach.
These results are then employed to point possible energysaving potentials,and to benefit the
decisionmaking process leading to more sustainable and cost-effective projects. This paper refers to the EU
collaborative research project called P2Endure. This project focused the practical development and
implementation of Plug-and-Playsolutions and tools for deeprenovation projects of residential as well
as public building (
Determining and predicting the energy consumption is a critical and equally important input for
planning and controlling the energy performance of a building
At the European level, various research projects have devoted themselves over the past few years to optimizing the planning, implementation and control of construction projects. Holisteec, a H2020 funded research project, developed a Building Information Model (BIM) based collabora tive software platform with the aim of designing, implementing and controlling building plans after completion of the construction project. Holisteec aims to improve the overall process efficiency, cooperation and conflict resolution of all participants. At the same time, life cycle costs and errors in planning and execution are to be reduced. Another research project, which should be mentioned, is eeEmbedded. This project was also funded by the European Commission within the framework of H2020. Similar to Holisteec, a cooperative BIM-based simulation platform was developed. In addition to that, a holistic building design methodology, an energy system information model and an integrated information management concept for the design of energy-efficient buildings were presented. Within the project, knowledge-based templates were presented, which enable energy simulations already in the early project phases. Finally, Design4Energy, also a H2020 project, should be mentioned. The aim of this project was to develop methods to simulate future energy values of buildings. The baseline of this procedure are energy attributes of buildings, neighborhood energy systems, result-related parameters, Energy simulation tools as well as current consumer usage parameters. The process of product-centered representation for evaluating the energy efficiency of buildings has common features regarding this research. The present work is also focusing on optimizing the existing process for the evaluation and controlling of energy values. Our proposal also uses defined building model values or values of the building elements contained therein. On the other hand, our process, focuses on the exchange of elements from existing building models. We show a procedure with the help of which the simulation of different renovation options with one and the same building model.
In this section, we present the process of the product centric approach for assessing the energy performance of building renovations. We describe the structure of the buildings elements as well as the exchange of elements between the building energy models. Before we discuss the product centric approach, we start with a brief introduction about the demonstration case, which we use within this paper.
The case study for testing and demonstrating our approach, is a real existing building located in Warsaw, Poland. The case study is a two storey kindergarten, which was constructed in 1965. The building volume is 2712 m3. Through a deep retrofitting procedure, the energy consumption of the building, especiallyfor heating, are to be reduced. Therefore, the plan is to install new windows as well as a new Plug-and-play façade. To monitor the renovation process, a building energy model was created. Within this paper, we use this energy model to demonstrate the aim of our approach. Based on the demonstration project in Warsaw, the design exchange was performed by two entity classes and parameters, windows and panels. First, the old windows of the kindergarten will be replaced by new windows in the course of the renovation project. The new windows have values specified by the manufacturer. The size and number of the windows will remain the same after the renovation. The old windows had single glazing. The new windows will be double or triple glazed. The windows can also be rotated around their own axis. The interior and exterior glazing have different parameters in terms of light transmittance. By rotating the windows, the amount of light entering the room can be reduced, thus reducing the amount of light in summer. Table 2 presents the values of the old window, while table 3 demonstrate the new windows, that will be integrate as part of the renovation process.
W/ m2K Obj. 1 V06_ Window_PVC 1,5 0,7 Obj. 2 V07_ Window_PVC 1,5 0,7 Obj. 3 V08_ Window_PVC 1,5 0,7 Obj. 4 V09_ Window_PVC 1,5 0,7
W/ m2K
Obj. 1 V09_ Window_PVC 0,9 0,53
Obj. 2 V10_ Window_PVC 0,9 0,53
Obj. 3 V03_BGTec 0,9 0,27
Obj. 4 V08_ Window_PVC 0,9 0,53 Second, Plug-and-Play external façade panels will be installed. The façade values are also specifiedby the manufacturer. Table 3 presents the values of the external panel according to the manufacture. The façade consists of several elements with different characteristics. The left side on figure 1 indicatesthe installation of the new façade. A panel installation shaft connects the whole panel with the external wall. The right side of figure 1 presents a schematic illustration of the façade with the individual elements described in Table 3. In our approach, we use EnergyPlus to perform the simulation of the buildings energic values. EnergyPlus is an energy simulation code with a modular structure . It uses the IDF data format for input data. IDF consists of architectural- and mechanical design elements. Space boundaries, shadi ng and thermal view are part of the architectural design. These design features are important to build to geometry for the IDF file. The architectural design consists of thermal properties of construction material. These construction properties are also needed for the IDF file to run the energetic simulation (National Renewable Energy Laboratory (NREL), 2019).
We classify our process into three overall process phases. At the end of a process step, results are generated that serve as input parameters for the following sections. Within the first phase, we define the building elements. Each element is defined by attributes. These attributes are product specific. Based on these specific attributes for describing the building classes, we can build types of products. We then classify these product types into product classes in the product class layer. The sum of the elements of all product classes is the description of the building energy model.
In the second phase, the simulation of the building energy model takes place. The outcome of the second process step are the simulated energetic valuesbasedon the chosen renovation options.These values are the input for the third and last phase. Here, the visualization of the energetic values takes place. Within this paper, we want to focus on the process steps one and two. The third phase is not part of the scope. Below, we describe the process steps 1 and 2 in more detail. Figure 2 presents the overall process with the three internal process steps.
As shown in Figure 2, multiple simulations are required to determine the best selection of design options. In the traditional approach, different energy models with integrated renovation elements must be created and then tested through an energy simulation program (e.g. EnergyPlus). Our approach preserves the existing energymodel. Only the elementsto be renovatedare replaced by new components. This replacement does not take place in EnergyPlus. For this we use an algorithm developed by us, which changes the file of the energy model according to the design options. Components that need to be renovated are replaced by the same types.
In the first process step we define the classes of products. Following our case study, we describe the class definition using the example of windows and facades. To define product classes, attributes are required to describe the properties of the class. Here, we adapt the respective class descriptions for building elements of EnergyPlus. Figures 3 illustrate the structure of the product classes façade and window. According to figure 3, we illustrate the groups of parameters necessary for the creation of the facade and window classes. On the left of figure 3, a façade element is shown. A facade consists of one or more material elements. In figure 3, an example of a facade panel with only one material is shown. Accordingly, a parameter group is sufficient to describe the material of the facade. If the facade consists of several elements, a parameter group is used for each element to describe it. This n -number of the describing parameter groups are combined in the entire façade element class. The Windows class consists of two parameter groups. The first group describes the properties of the window. The second group describes the glazing system.
The parameters shown in Figure 3, are without values. These values will be added according to the properties of the respective facades or windows. The parametric description of the classes completes the first phase of the process. At the same time, the product classes describe also the interface for the second phase of the process.
This second phase of the process is characterized by three internal process steps. In the first process step, the as-is building energy model is analyzed regarding the building elements to be renovated. According to the renovation plan described in chapter 3, all windows are replaced by new doubleglazed windows. For the analysis, we developed a context-dependent algorithm to examine the building energy model according to the classes to be replaced. parameters also needs to be included Figure 4 shows an excerpt from the energy model. In order to completely remove the old windows, the construction feature must also be removed. Figure 4shows the properties required to replace the windows. “GAP-MATERIAL-GLASS” describes the properties of the glass used in the existing building. In addition to these parameters, the “GAP-CONSTRUCTION” properties must also be considered and adapted or replaced. The parameters for “GAP-MATERIAL FRAME” are not considered within our model.
After the data has been removed from the model, the second internal process step starts. The instances of the new windows are inserted. At the moment we arrange the new values at the end of the building energy model. The placement of these elements is not decisive for EnergyPlus. After the new elements have been inserted, the third process step, the new simulationof the energy model,can start. The results of this simulation are the input values for the third phase of our proposed process.
Section 5 presents the method behind the product centric exchange of elements in building energy models and describes the process of finding, adding or replacing construction objects in the model. Within this section,we describe the outcome of our product centric approach. Therefore, we compare the energic consumptions of the different renovation options.
Table 4 shows the outcome of the energy simulation based on the performance parameter “Total Site Energy”, “End Uses” and “Energy Use Summary”. We compare these parameters with four different renovation option. The baseline for further considerations is the building energy model of the demonstration project in Warsaw. The energetic values of the performance parameters describe the situation before any kind renovation activity takes place. Our product centric approach allows use, to add and remove building elements within the as-is building energy model. Within table 4, we present the energetic values of the building energy model with a) additional external facades, b) new window, c) external façade as well as new window. To compare the different design options, we also present the energetic values of the as-is building energy model.
The first renovation option describes the integration of an exte rnal façade element. The energetic values are significantly improved by adding the new construction element. For example, the value for Total Energy decreases from 211325.3 to 161776.79. In option b) we replaced the old windows of the building withnew ones. The panels from option a) are not integrated. A significant reduction in energy consumption is also noticeable. In option c) we added the external panels as well as the new windows. Compared to the renovation options a), b) and the as-is building energy model, Option c) is the best solution for renovation in terms of energy consumption.
Comparison of different products within the building energy model External facade panel and new window
Model with new windows Model with external facade panels
Original Model 0 50000 100000 150000 200000 250000 District heating
Total Energy Based on the results, we can demonstrate the benefits of our approach. With the process of our approach, we only change elements of the energy model, not the whole model. Therefore, we enable a fast and comparable way of simulating and displaying energy data. The as-is energy model serves as the baseline for the further simulation of the different renovation options.
Within this paper, only windows and panels are considered as renovation options. Based on Tables 4 and 5, however, we demonstrate the benefits of our approach. The exchange of individual elements of an energy model under the assumption that all other elements of the building energy model, which are not affected by the exchange, remain unconsidered, enables a precise prediction of the energetic results of different renovation options. Figure 5 shows a possible operationprocess. We integrate our product centric data exchange approach into an application, which presents the outcome of the simulation results of the different renovation options. The potential user group can be reached from a homeowner with a single renovation project up to a municipality, who wants to renovate various buildings with nearly same construction features. Based on the initial values,the software simulatesand represents energetic values of the as-isbuilding energy model. The user will get the initial energetic valuesof the building as the baseline for the further suggestions. As a second process step, building elements according to his renovation project can be add or replaced. Based on the design decision, the energy values are simulated and displayed again. Consider that, our approach can offer an energetic comparison and predictionof energetic values. The forecast of building energy consumptions regarding various renovation options can improve the outcome energy results and reduce unforeseen costs.
The paper presents a procedure to close the existing gap in the representation of building energy models in renovation projects. The procedure focuses on a product-centered approach. Renovation products can be exchanged within the existing energy model of the object to be renovated. Thus, various design options can be analyzed without having to create new energy models.Within the work we have demonstrated this approach by replacing window elements and adding new external facades. The intention of this work is to present a variant in order to make the optimal decision between building design and energy target values already during the planning of renovation projects. At the same time, this work would like to support future research efforts with a f ocus on product-centred assessment. On the other side, this paper wants to motivate for future research in the field of product centered assessment of the energy performance, especially in renovation projects. During the coming months we will continue to expandour process and be able to map more product types, such as HVAC systems, through our product-centered process.
Funding: This research was funded by the European Union’s Horizon 2020 research and innovation program grant number 723391.