=Paper=
{{Paper
|id=Vol-2394/paper02
|storemode=property
|title=A Product-Centric Approach for Assessing the Energy Performance of Solution for Building Renovations
|pdfUrl=https://ceur-ws.org/Vol-2394/paper02.pdf
|volume=Vol-2394
|authors=Christoph Bindal-Gutsche,Timo Hartmann
|dblpUrl=https://dblp.org/rec/conf/egice/Bindal-GutscheH18
}}
==A Product-Centric Approach for Assessing the Energy Performance of Solution for Building Renovations==
https://ceur-ws.org/Vol-2394/paper02.pdf
A product-centric a pproach for assessing the energy performance of solution for building renova tions
A product-centric approach for assessing the energy performance of
solution for building renovations
Christoph Bindal-Gutsche, Timo Hartmann
Technical University Berlin, Germany
christoph.gutsche@tu-berlin.de
Abstract: 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 intensive. 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
Keywords: Building Energy Model (BIM), Product-centric simulation, Building renovation, energy-
efficient buildings
Introduction
According to Buildings Performance Institute Europe, 40% of the energy consumed and 36% of CO2
emissions in the European Union are related to buildings (European Commission, 2019). 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). Moreover, the renovation of the building stock is
the most viable solution to reduce energy consumption and CO2 emissions (Nägeli, Camarasa, Jakob,
Catenazzi, & Ostermeyer, 2018, p. 444).
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 (Harvey, 2009, p. 140). To obtain a good renovation strategy in
terms of improving the energetic values of the building, models for analyzing and predicting the energy
balance are suitable.
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 (Vollaro, et al., 2014, p. 87). Most of the time, building energy models are
generated based on building information models. These generated models are often inaccurate and
difficult to make established statements. Nevertheless, building energy performance assessment is
necessary to ascertain the efficiency of energy use in buildings. Moreover, it is the basis to make any
decision to enhance the buildings energy efficiency.
In our approach, we want to present a method how to build energy models by changing elements of
the building model. Based on Building Energy Models from real construction projects, we want to show
the energetic effects by changing the elements for renovation within the model. As input variables, we
use weather conditions, building description and building component descriptions. The inputs for
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A product-centric a pproach for assessing the energy performance of solution for building renova tions
component description include 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 (Borgstein, Lamberts, & Hensen, 2016, p. 477). Laying the focus on the renovation
products, we present the different energy performances for building renovations. Accounting the
properties of the structures can allow an accurate modelling procedure that reflects the building
energy consumption based on the different product values. Analysis of buildings can lead to correctly
estimate the building energy performance. However, this type of analysis is often limited to simple
technological upgrades and assume, that the environmental conditions were identical before and after
renovation.
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 buildings with there elements. In addition to that, EnergyPlus runs 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 energy saving potentials, and to benefit the decision-
making 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-Play solutions and tools for deep renovation projects of residential as well
as public building (P2Endure, 2019).
1. Optimization and energy model in construction projects
Determining and predicting the energy consumption is a critical and equally important input for
planning and controlling the energy performance of a building (Xiaoshu, Tao, Charles J., & Martti,
2015). A detailed and accurate building energy model thus provides an outlook on the expected energy
values of the building (Arayici, et al., 2011). These energy values are the basis for the selection and use
of various building elements in accordance with the requirement to achieve energy target values.
Various design options can be compared against each other duri ng the planning phase in order to find
the optimal solution for the construction of a building. Creating building energy models requires
significant effort. However, the need for such models is increasing (Giannakis, Lilis, Kontes, & García-
Fuentes, 2015). There are also numerous publications in the literature that focus on the creation of
building energy models. The focus, then as now, is the generation of energy models from existing
building models. One of the first efforts for a transformation into energy models are already more than
two decades old. Earlier applications of the Lawrence Berkeley National Laboratory (LBNL) started to
extract rudimentary geometries of building elements from instances of buildi ng information models
and converting them into an Input Data File (IDF) for EnergyPlus (Hitchcock & Wong, 2011). Olof
Granlund Oy, a building service company from Finland, developed middleware software more than 20
years ago, which can convert elements from a building model to an IDF format without requiring the
user to have detailed knowledge of the elements (Karola, et al., 2001). The Architecture, Engineering,
Construction, Owner Operator, Phase 1 (AECOO-1) Years later, Testbed started the attempt to
optimize the data exchange during the development phase of a building in order to reduce costs and
improve the Building Performance Energy Analysis (BPEA). The BPEA thread focused on defining and
documenting data exchange requirements for early design energy analysis (Hitchcock & Wong, 2011).
New applications, such as the Green Building Web Services, convert special gbXML descriptions of the
building into data formats that can be loaded by the EnergyPlus software, among others. Object-
oriented frameworks for the optimization of green buildings have been developed (Wang, Jing, Zhang,
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A product-centric a pproach for assessing the energy performance of solution for building renova tions
& Zhao, 2009) and also optimization processes to develop a collaborative design framework (Bleiberg
& Shaviv, 2007). Component-oriented frameworks were presented to facilitate multi -disciplinary
design optimization (Geyer, 2009).
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 collaborative 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.
2. Case study
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, especially for 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.
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A product-centric a pproach for assessing the energy performance of solution for building renova tions
Table 1: Window objects from the original building energy model
Field Units Obj. 1 Obj. 2 Obj. 3 Obj. 4
Name V06_ V07_ V08_ V09_
Window_PVC Window_PVC Window_PVC Window_PVC
U-Factor W/ m2K 1,5 1,5 1,5 1,5
Solar Heat Gain 0,7 0,7 0,7 0,7
coefficient
Table 2: New values of the windows, which will be integrate into the original building energy model
Field Units Obj. 1 Obj. 2 Obj. 3 Obj. 4
Name V09_ V10_ V03_BGTec V08_
Window_PVC Window_PVC Window_PVC
U-Factor W/ m2K 0,9 0,9 0,9 0,9
Solar Heat Gain 0,53 0,53 0,27 0,53
coefficient
Second, Plug-and-Play external façade panels will be installed. The façade values are also specified by
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.
Table 3: Attributes and values of the new panel
Density Thickness Λ R Diff. -
Material [kg/m3] s[mm] [W/mK [m2 K/W] Wid
Structure of the field area
Air passage warm side Rsi 0.13
Mineral wool 04 20 50 0.040 1.250 1
Fermacell gipsum fibre 1150 Dez 50 0.320 0.039 13
Vapour break 1100 0.2 0.2 0.1 100000
Mineral wool 035 50 200 0.035 5.714 1
Fermacell Powerpanel 950 15 0.3 0.05 40
Light mortar LM 21 700 10 0.21 0.048 15/35
Air passage cold side Rse 0.04
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A product-centric a pproach for assessing the energy performance of solution for building renova tions
Figure 1: Construction plan of the external facade
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, shading 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).
3. Product centric assessement process
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 values based on 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.
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A product-centric a pproach for assessing the energy performance of solution for building renova tions
Figure 2: Overall process where we build product classes based on attributes (phase 1), run the simulation based on the
chosen renovation option (phase 2) and present the results (phase 3).
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 energy model. Only the elements to be renovated are 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.
Process step 1
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.
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A product-centric a pproach for assessing the energy performance of solution for building renova tions
Figure 3: Description of the attributes for the renovation product class Material 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.
Process step 2
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 double-
glazed windows. For the analysis, we developed a context-dependent algorithm to examine the
building energy model according to the classes to be replaced.
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A product-centric a pproach for assessing the energy performance of solution for building renova tions
Figure 4: Presentation of the class window within the building energy model. To cut out the old window, construction
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 4 shows 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 simulation of the energy model, can
start. The results of this simulation are the input values for the third phase of our proposed process.
4. Results and outlook
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 with new 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.
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A product-centric a pproach for assessing the energy performance of solution for building renova tions
Table 4: Comparison the energetic results bases on different products (renovation options) within the building energy model
Performance parameters As-is building a) Model with b) Model with c) Model with
energy model external new windows new window
facade panels and external
facade panels
Total Site Total Energy 211325.30 161776.79 206728.27 151861.20
Energy in [kWh]
Energy Per 154,05 91,53 150,70 85,92
Total Building
Area
[kWh/m2]
Energy Per 166.22 97.05 162.60 91.10
Conditioned
Building Area
[kWh/m2]
End Uses District 179243.29 123207.33 174646.26 113291.74
heating [kWh]
Energy Use Total [kWh] 211325.47 161776.92 206728.43 151861.32
Summary
Table 5 visualize the energetic outcome of the three renovation options as well as the energy values
of the as-is building energy model.
Table 5: Visualisation of the energetic comsumption based on different products within the energy model
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.
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A product-centric a pproach for assessing the energy performance of solution for building renova tions
Using a short application example, we want to propose a possible outlook of our approach.
Figure 5: Preparing of energy consumption forecasts based on product centric data exchange within the building energy
model
Figure 5 shows a possible operation process. 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 simulates and represents energetic values of the as-is building
energy model. The user will get the initial energetic values of 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 prediction of energetic values. The
forecast of building energy consumptions regarding various renovation options can improve the
outcome energy results and reduce unforeseen costs.
5. Conclusion
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 expand our 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.
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