Using Specification and Description Language for

sustainability Article

Using Specification and Description Language for Life Cycle Assesment in Buildings Pau Fonseca i Casas 1, * and Antoni Fonseca i Casas 2 1 2

*

Statistics and Operations Department, Universitat Politècnica de Catalunya, Barcelona-Tech, 08034 Barcelona, Spain Polyhedra Tech SL, 08026 Barcelona, Spain; [email protected] Correspondence: [email protected]; Tel.: +34-934-017-732

Academic Editor: Avi Friedman Received: 10 March 2017; Accepted: 5 June 2017; Published: 10 June 2017

Abstract: The definition of a Life Cycle Assesment (LCA) for a building or an urban area is a complex task due to the inherent complexity of all the elements that must be considered. Furthermore, a multidisciplinary approach is required due to the different sources of knowledge involved in this project. This multidisciplinary approach makes it necessary to use formal language to fully represent the complexity of the used models. In this paper, we explore the use of Specification and Description Language (SDL) to represent the LCA of a building and residential area. We also introduce a tool that uses this idea to implement an optimization and simulation mechanism to define the optimal solution for the sustainability of a specific building or residential. Keywords: Specification and Description Language (SDL); Life Cycle Assesment (LCA); smart cities; IoT; buildings simulation; sustainability; resilience

1. Introduction Currently, there is worldwide awareness of the global increase in energy consumption and the limited amount of resources available to provide energy to citizens and enterprises. This creates a huge energy demand and the need to define a new economy and transition methods to increase energy savings [1]. Considering more effective methods to reduce energy consumption in residential and commercial areas is strongly related to building efficiency, which has a great impact on electricity consumption. Although electricity represents only a part of the total energy consumption, it clearly reflects the importance of the building in the global impact. In the USA, the residential sector represents approximately 38% of the electricity consumed and in the commercial area, approximately 36% [2]. The Life Cycle Assesment (LCA) in a building or an urban area helps to obtain a clear image of all processes involved in the planning, construction, use, and deconstruction of a house. This holistic view can assist in the reduction of the impact, taking care of the economic, social, and environmental aspects in a cradle to cradle approach [3]. From an environmental point of view, reducing energy consumption would have a great impact in decreasing the environmental impacts. In addition, the analysis of the LCA for houses has a great impact on energy consumption in all sectors, not only in houses, but also shows a foreseeable greater impact on the residential and commercial sectors that represent a huge part of the total. For example, all materials that must be used in a building must be transported from several different origins to its final destination of the building. By incorporating these parameters in the model, we can also reduce the emissions from transportation, which are huge.

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2. State of the Art Building or residential area LCA is complex, mainly because it needs to use powerful tools to scope the complex dynamics of the environment and the energy. Several problems arise with this type of analysis and includes the amount and the diversity of the data that must be used, and the fact that this area utilizes different specialists working with different skills in multidisciplinary teams. Mainly, these problems are related to the choice of unit of the analysis and the methodological and practical approaches used [4]. In this context, some approaches have been undertaken to improve the LCA application in architecture [5,6]. A complete review of the development of the LCA in the field of architecture can be found in the studies presented by [7,8]. By 31 December 2020, EU directive 2010/31/EU requires that all new buildings must be nearly zero-energy buildings (nZEB). The aim of this directive is to incorporate concepts for reducing their impact on the environment [9]; thus, the member states must also complete the thresholds and policies to update their building stock [10–13]. Member states have launched a series of projects, actions, and policy guidelines to specify the optimal cost-performance actions to achieve the objectives proposed by the regulation on energy rehabilitation (Royal Decree 235/2013). This allows researchers to check which urban areas are in the greatest need of rehabilitation and/or that suffer from so-called “energy poverty” [14]. Furthermore, several European and national projects have been proposed [15,16] to provide funding for initiatives which, in addition to addressing the issue of energy efficiency either for new construction or rehabilitation, also include the impact of construction on the environment; that is to say, be capable of conducting a LCA (Life Cycle Assesment) of the building and thereby ascertain its associated impacts. Such concepts must be addressed to complete the analysis, not solely in terms of energy and economic cost. To perform a comprehensive study of sustainability, one must include the proposed European standards developed by the CEN TC 350 Working Group, and implemented nationally via Standard UNE EN 15643 on the Sustainability of Construction Works [17]. This set of standards describes and specifies the impacts that must be considered (environmental, economic and social impacts), details indicators, and proposes methodologies. If we consider the criteria and objectives that must be achieved based on the above-mentioned standards, programs and applications must be employed to simulate energy consumption, calculate economic and environmental impacts, and conduct a complete LCA. No global proposals exist for analyzing certain parameters. Often the designer or engineer has to invest a significant amount of time designing a virtual model just to study a few design iterations to identify a good solution. The designer is not in a position to ensure that the best solution is adopted, or at least one of the best solutions, without analyzing all, or an accurately selected subset, of the possibilities. In addition, most commercial simulation software packages allow for a building’s annual energy analysis to be calculated, but do not perform any kind of optimization for the process. Hence, none of the results for the previous steps, such as the design, construction, or demolition processes, are optimized. Efforts have been made to develop approaches and methods for assessing buildings [18], methods for integrating daylight and thermal efficiency [19–21], photovoltaic systems [22], and multi-objective optimization systems into urban design [23], which consider several aspects when creating an energy optimization system. Languages that are commonly used for programming simulators or optimization tools are C++, C#, Fortran, Java and Delphi, among many others. The use of different languages may cause problems with integration, model determination and understanding between researchers from different disciplines, as not everyone understands the low-level code finally used. One of the proposals presented in this work is the use of a formal language to simplify model definition and use. The use of formal languages, such as Discrete Event System Specification (DEVS) [24], Specification and Description Language (SDL) [25,26], or Petri nets [27], is without a doubt one of the best solutions. These languages allow for an easy integration and communication of ideas related to


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the model with the other members of the team. Additionally, these tools improve interoperability with other models (co-simulation) and promotes cooperation. Examples of recent works that explore the use of official languages in this area are [28,29], which explore the use of the co-simulation approach for calculating building HVAC systems (heating, ventilation, and air conditioning). To represent this LCA, we used a discrete simulation model formalized using Specification and Description Language (SDL). In this area, several approaches exist, mainly ruled by the tools used. Classical languages like GPSS/H® [30], Slam II® [31], or others considered more modern like Simprocess® [32], Arena [33], or SIMIO [34], among many others, can be used. These software packages allow a complete definition of the model behavior, structure, time and representation; however, once the model is defined in one of these simulation packages, it is often difficult to migrate to another. All specialists who interact with the model must also understand how the tool works. In this context, the use of formal language to represent the model and to later use a specific tool to implement the model is necessary, even more so if the model is complex or the personnel working on the model own different forms or, do not know how to implement the model in the specific tool selected to perform its implementation. Programming libraries and infrastructures exist that allow for the definition of a simulation model following a formal language. The tools related to DEVS [35–37] and PetriNets formalisms [27] often represent an excellent alternative to define and implement a simulation model based on Petri nets or DEVS. Specifically to model buildings and their related processes, several experiences exist using DEVS as a language, based on the BIM (Building Information Modeling) philosophy, see [28,38], but no experiences trying to model the entire LCA of a house or urban area have been found. SDL is not new for modeling energy-related issues. [39] presented two complementary approaches to specify energy aspects during the design phase of wireless networks, but like DEVS, no studies that model the LCA of a building exist. In this paper, we describe our experience of using SDL to describe the main processes that define the LCA of a building and show how to take advantage of a formal representation to expand the model implementation easily over different platforms. The paper is organized as follows: in Section 3, we describe the SDL based model we use; in Section 4, we discuss how to implement this model; in Section 5, we describe how to execute the model on the web using a cloud infrastructure. Finally, Section 6 contains our conclusions. 3. Methodology One of the aims of this research was to describe, as formally as possible, the structure and behavior of the LCA of a building. This goal was crucial as the people involved are diverse and come from many different backgrounds. To address this issue, we used SDL to formally define the model. The use of the SDL language afforded maximum flexibility to integrate new processes and procedures to the system in a co-simulation scenario [29]. Using a graphical formal language allowed nonspecialized technicians access to the programming details of the model and definitively contributed to the validation and verification processes. In addition, the explanation of the model itself was more intuitive, simple, and direct than using a programming language such as C or Java. Thus, the group can share the model, making it much easier to understand and detect errors, as well as propose improvements. 3.1. Specification and Description Language In this section, we do not describe specifically how SDL behaves, more information on this language can be found in [25,26]. However, we want to note that the graphical capabilities, the completeness, and lack of language ambiguity makes it a great candidate to formally define any kind of simulation model. Specification and Description Language (SDL) is an object-oriented, formal language defined by The International Telecommunications Union-Telecommunications Standardization Sector [25], formerly Comité Consultatif International Telegraphique et Telephonique (CCITT), in recommendation Z.100. The language is intended for the specification of complex, event-driven, real-time, and

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interactive applications involving manyto concurrent activities that communicate using processes, discrete signals. discrete signals. SDL uses four levels describe model behaviors: system, blocks, and discrete signals. SDL uses four levels to describe model behaviors: system, blocks, processes, and discretesignals. signals.SDL SDLuses usesfour fourlevels levelsto todescribe describemodel modelbehaviors: behaviors:system, system,blocks, blocks,processes, processes,and and discrete signals. SDL uses four levels to describe model behaviors: system, blocks, processes, and discrete SDL uses four levels to describe model behaviors: system, blocks, processes, and procedures, see procedures, see Figure 1. procedures, see Figure 1. procedures, see Figure 1. procedures, see Figure 1. procedures, see Figure 1. Figure 1.

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The different model concepts that the SDL formalism describes are (i) Structure: system, blocks, The different model concepts that the SDL formalism describes are (i) Structure: system, blocks, Thedifferent differentmodel modelconcepts conceptsthat thatthe theSDL SDLformalism formalismdescribes describesare are(i) (i)Structure: Structure:system, system,blocks, blocks, The different model concepts that the SDL formalism describes are (i) Structure: system, blocks, The processes and processes hierarchy; (ii) Communication: signals, along with the parameters and processes and processes hierarchy; (ii) Communication: signals, along with the parameters and processes and processes hierarchy; (ii) Communication: signals, along with the parameters and processes and and processes processes hierarchy; hierarchy; (ii) (ii) Communication: Communication: signals, signals, along along with parameters and processes the processes and processes hierarchy; (ii) Communication: with the parameters parameters and channels that the signals use to travel; (iii) Behavior: defined through the different processes; (iv) channels that the signals use to travel; (iii) Behavior: defined through the different processes; (iv) channels that the signals use to travel; (iii) Behavior: defined through the different processes; (iv) channelsthat thatthe thesignals signalsuse use travel; (iii) Behavior: defined through thedifferent different processes; (iv) channels signals use travel; (iii) Behavior: defined through the processes; (iv) channels that tototo travel; (iii) Behavior: defined through the different processes; (iv) Data: Data: based on Abstract Data Types (ADT); and (v) Inheritances: to describe the relationships Data: based on Abstract Data Types (ADT); and (v) Inheritances: to describe the relationships Data:based based onAbstract Abstract Data Types (ADT); and(v) (v)Inheritances: Inheritances: todescribe describethe therelationships relationships Data: based on Abstract Data Types (ADT); and (v) Inheritances: to describe the relationships Data: on Data Types (ADT); and based on Abstract Data Types (ADT); and (v) Inheritances: to describe to the relationships between, and between, and specialization of, the model elements. between, and specialization of, the model elements. between, and specialization of, the model elements. between,and andspecialization specialization of,the themodel modelelements. elements. between, of, specialization of, the model elements. System diagrams, i.e., block diagrams describing the model structure, represent hierarchical System diagrams, i.e., block diagrams describing the model structure, represent hierarchical Systemdiagrams, diagrams,i.e., i.e.,block blockdiagrams diagramsdescribing describingthe themodel modelstructure, structure,represent representhierarchical hierarchical System diagrams, i.e., block diagrams describing the model structure, represent hierarchical System structure, represent hierarchical decompositions of the different model elements; some good examples can be reviewed in [26]. [26]. A A decompositions of the different model elements; some good examples can be reviewed in decompositions of the different model elements; some good examples can be reviewed in[26]. [26]. A of the different model elements; some good examples can bereviewed reviewed in [26]. 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Start. This element defines the initial condition for a PROCESS diagram. Start. This element defines the initial condition for PROCESS diagram. Start. This element defines the initial condition for PROCESS diagram. Start. This element defines the initial condition for aaaPROCESS diagram. Start. This element defines the initial condition for aaPROCESS PROCESS diagram. Start. This element defines the initial condition for diagram. State. The state This defines the states of State. The state element contains the name of state. This element defines the states of State. stateelement elementcontains containsthe thename nameof ofaaa state. state. Thiselement element defines the states of State. Thestate state.This statesof of State. The state element contains the name state. This elementdefines definesthe thestates states of State. The element contains the name ofofaaastate. element behavioral diagrams, such as PROCESS diagrams. behavioral diagrams, such as PROCESS diagrams. behavioral diagrams, such as PROCESS diagrams. behavioral diagrams, such as PROCESS diagrams. behavioraldiagrams, diagrams,such suchas asPROCESS PROCESSdiagrams. diagrams. behavioral Input. Input elements describe the of events that can be received by the process. All Input elements describe thetype type events that can be received by the process. Input. Input. Input elements describe the type of events that can be received by the process. All Input. Inputelements elementsdescribe describethe the type ofof events that can bereceived received bythe theprocess. process. All Input. Input elements describe the type events that can be received by the process. All Input. Input type ofof events that can be by All branches of a specific state start with an Input element because an object only changes its state when All branches of a specific state start with an Input element because an object only changes its state branches of a specific state start with an Input element because an object only changes its state when branchesofof ofaaaspecific specificstate statestart startwith withan anInput Inputelement elementbecause becausean anobject objectonly onlychanges changesits itsstate statewhen when branches specific state start with an Input element because an object only changes its state when branches aawhen new event received. aevent newis event is received. new event is received. a new is received. newevent eventisisreceived. received. aanew Create. This element allows the creation of an agent. Create. This element allows the creation of an agent. Create. This element allows the creation of an agent. Create. Thiselement elementallows allowsthe thecreation creationof ofan anagent. agent. Create. This element allows the creation of an agent. Create. This Task. This element allows the interpretation of informal texts or programming code. In this Task. This element allows the interpretation of informal texts or programming code. In Task. This element allows the interpretation of informal texts or programming code. In Task. This element allows the interpretation of informaltexts textsor orprogramming programmingcode. code.In In Task. Thiselement element allowsthe the interpretation ofinformal informal texts or programming code. In Task. This allows interpretation of paper, following SDL-RT (PragmaDev SARL, 2006), we used C code. this paper, following SDL-RT (PragmaDev SARL, 2006), we used C code. this paper, following SDL-RT (PragmaDev SARL, 2006), we used C code. thispaper, paper,following followingSDL-RT SDL-RT(PragmaDev (PragmaDevSARL, SARL,2006), 2006),we weused usedCC Ccode. code. this paper, following SDL-RT (PragmaDev SARL, 2006), we used code. this Procedure call. These elements perform a procedure call. A can be defined Procedure call. These elements perform procedure call. AAPROCEDURE PROCEDURE can be defined Procedurecall. call. Theseelements elementsperform performaaaaprocedure procedurecall. call.A PROCEDUREcan canbe bedefined defined Procedure call. These elements perform procedure call. APROCEDURE PROCEDURE can be defined Procedure These in the last level of the SDL language and used to encapsulate pieces of the model for reuse. in the last level of the SDL language and used to encapsulate pieces of the model for reuse. inthe thelast lastlevel levelofof ofthe theSDL SDLlanguage languageand andused usedtoto toencapsulate encapsulatepieces piecesofof ofthe themodel modelfor forreuse. reuse. the last level the SDL language and used encapsulate pieces the model for reuse. inin

proposed to UML, such as SysML or AUML, that extends the langu Input. Input elements describe the type of events can bemodel received by thethat process. All formalism describ Thethat different concepts the SDL branches of a specific state start with an Input element because an object only changes its state when processes and processes hierarchy; (ii) Communication: signal a new event is received. channels that the signals use to travel; (iii) Behavior: defined th

Create. This element allows the creation ofData: an agent. based on Abstract Data Types (ADT); and (v) Inheritan 5 of 17 Task. This element allows the interpretation of informal texts or programming code. In between, and specialization of, the model elements. Sustainability 2017, 9, 1004 5 of 17 this paper, following SDL-RT (PragmaDev SARL, 2006), we used C code. System diagrams, i.e., block diagrams describing the mode decompositions ofPROCEDURE the different model elements; Procedure call. These elements perform a procedure call. PROCEDURE can bebe defined in some good exa Procedure elements perform a procedure call. can defined Sustainability 2017, 9,call. 1004 5 ofthe 17 Output. Output These elements describe the types of signals toAA be sent, the parameters that process diagram defines the behavior of the agents when a sp the last level ofand thethe SDL language and used to to encapsulate of thethe model forfor reuse. in the last level of SDL language used encapsulate pieces of model reuse. signal carries, the destination. Ifand ambiguity about the pieces signal destination exists, communication different graphical elements to represent its the behavior. Output. Output elements describe the types of signals signals to be bevalue sent, the parameters parameters that the Output. elements describe the of to sent, the that can be directed byOutput specifying destinations using atypes processing identity (PId), an agent name, or signal carries, and the destination. If ambiguity about the signal destination exists, communication can signal carries, the destination. If ambiguity about the signal destination exists, communication using the sentence via path. If there is more than one path specific output is defined, an condition for a P Start.and no This element defines the initial be directed by specifying destinations using a processing identity value (PId),(PId), an agent name, or using can be directed specifying destinations using a processing identity value an agent name, or arbitrary one isbyused. The destination value can be stored in a variable for later use. Four PId State. The state element contains the name of a state. the sentence via be path. If there more one path and no parent, specific output isoutput defined, an the arbitrary using the sentence via path. Ifisthere isthan more than one path and nothe specific is defined, an expressions can used: (i) self, an agent’s own identity; (ii) agent created agent behavioral diagrams, suchthat as PROCESS diagrams. one is used. The destination value can be stored in a variable for later use. Four PId expressions can arbitrary one is used. The destination value can be stored in a variable for later use. Four PId (Null for initial agents); (iii) offspring, the most recent agent created by the agent; and (iv) sender, the Input. describe the type of events that be used: self,the anused: agent’s identity; (ii) parent, the agent that created theelements agent (Null for agent initial expressions can be (i) own self, an agent’s own identity; (ii) parent, the Input agent that created the agent that(i)sent last signal input (null before any signal received). branches of aand specific state start anthat Input agents); offspring, recentthe agent created the agent; (iv) agent; sender, thewith agent sent (Null for (iii) initial agents);the (iii)most offspring, most recentby agent created by the and (iv) sender, theelement because an Decision. These elements describe bifurcations. Their behavior depends on how the related a newreceived). event is received. the last signal (null before any(null signal received). agent that sent input the last signal input before any signal question is answered. Create. element allows creation of an agent. Decision. Their behaviorThis depends onhow how thethe related Decision. elements describe bifurcations. Their behavior depends on the related The last levelThese of the SDL language (PROCEDURE diagrams) allows the description of Task. This element allows the interpretation of inform questionisisanswered. answered. question procedures that can be used in the PROCESS diagrams through the procedure calls . These this paper, following SDL-RT SARL, The last thethe SDLSDL language (PROCEDURE diagrams) allows the description of procedures The last level levelof of language (PROCEDURE diagrams) allows the(PragmaDev description of 2006), we used diagrams are very similar to the PROCESS diagrams with the exception that they do not need state that can be that usedcan in the through the procedure calls . These These diagrams are Procedure call. perform a procedure c procedures be PROCESS used in thediagrams PROCESS diagrams through the procedure callselements . These definitions. very similar to the PROCESS diagrams with the exception that they do not need state definitions. the the lastexception level of the SDL language diagrams are very similar to the PROCESS diagrams in with that they do not and needused stateto encapsulate piec definitions. 3.2. The Model 3.2. The Model Here, the model is described with its main elements to understand the benefits of the approach. 3.2. The Model Here, the model is described with its main elements to understand the benefits of the approach. For a detailed description of the model please refer to [40]. Figure 2 shows the first level of the For aHere, detailed of the model please refer to [40].toFigure 2 showsthe thebenefits first level the building the description model ismodel. described withmain its main elements understand of of the approach. building simulation Four blocks represent the environment, the building, the simulation model. Four main blocks represent the environment, the building, the compensation and For a detailed description of the model please refer to [40]. Figure 2 shows the first level of the compensation and the waste treatments. the wastesimulation treatments. model. Four main blocks represent the environment, the building, the building compensation and the waste treatments. Sustainability 2017, 9, 1004

Figure 2. 2. SDL SDL system system diagram diagram detailing detailing the the main main components components of of the the model model considered considered in in the the study. study. Figure

Figure SDL system diagram detailing the main components of the model considered in the study. this2. model, the structure and behavior of the building LCA are described as formally as In this model, the structure and behavior of the building LCA are described as formally as possible. possible. The detailed description of the model helps in the validation process. The validation was The detailed description of the model helps in the validation process. The validation was done by a model, thethe structure behavior of the building LCA are described as system. formallyThis as doneInof bythis a team of on specialists on and the system, architects, and engineers who clearlythe understand the team specialists system, architects, and engineers who clearly understand possible. The type detailed description the modelofhelps in the validation process. The validation was system. This of validation (for validation the conceptual model, seeto[41]) is needed to depict type of validation (for validation ofof the conceptual model, see [41]) is needed depict the relationships done by a team of specialists on the system, architects, and engineers who clearly understand the the relationships between all the components that the experts depict as important for system system. This type of validation (for validation of the conceptual model, see [41]) is needed to depict behavior. Once this has been achieved, the structure of the model is complete, and one can start the relationships between all the components that the experts depict as important for system analyzing the model behavior. behavior. Once this has been achieved, the structure of the model is complete, and one can start analyzing the model behavior.

Every building is connected to energy (isolated or in a network) and to social networking (the residents), and these concepts must be modeled to complete the cycle, an idea already introduced in Cradle to Cradle [3] where we face a new paradigm of design (see Figure 3). This vision of the reality is characterized in the SDL model presented in Figure 2. The B1_Environment block encapsulates all processes related to the environment. For example, it Sustainability 2017, 9, 1004 6 of 17 represents the amount of radiation that the building receives, the hydrologic conditions, and so on. All of the information calculated in this BLOCK is sent to the B1_building block through data that between allallthe the experts depictB1_Building as important for system behavior. Once thisas has represents of components the required that weather information. is the main BLOCK of the model it been achieved, the structure of the model is complete, and one can start analyzing the model behavior. represents the main processes that rule the behavior structure of the building. B1_compensation Every building is connected to energy (isolated in a network) and to networking encapsulates the processes necessary to deliver theorenergy consumed bysocial the building and(the to residents), the andenvironmental these conceptsimpacts must be(through modeled the to complete the cycle, generation, an idea already introduced in neutralize process of energy for example, with Cradle to Cradle [3] where we face a new paradigm of design (see Figure 3). solar photovoltaic or CO2 gas absorption systems). Extraction of raw materials Reuse / recycling

Transportation

Use

Manufacturing

Distribution

Figure 3. Cradle to Cradle, Cradle,see see[3]. [3].Every Everyhouse house(and (andproduct) product) from point of view of the complete Figure 3. Cradle to from thethe point of view of the complete life life cycle. The phases that are now included in the are Transportation, defining a CO2 cycle. The phases that are now included in the model are model Transportation, defining a CO 2 consumption consumption for the materials; Manufacturing and defining Distribution, a CO2 consumption for the for the materials; Manufacturing and Distribution, a COdefining for the constructing 2 consumption constructing and Use, the main processes of the model that represents solutions; andsolutions; Use, detailed with detailed the mainwith processes of the model that represents the behavior of the behavior of the buildings during this phase. buildings during this phase.

B1_WasteTreatment represents the processes related to waste disposal. Each of the different This vision of the reality is characterized in the SDL model presented in Figure 2. blocks of the model is decomposed into a single process. The B1_Environment block encapsulates all processes related to the environment. For example, The main variables that the model uses are detailed in Table 1. The BIM model is represented by it represents the amount of radiation that the building receives, the hydrologic conditions, and the Energy+ format, idf files, and climatic information is represented on the andepw files. Several so on. All of the information calculated in this BLOCK is sent to the B1_building block through other factors (variables) can be modified in the model to define the scenarios to be executed. data that represents all of the required weather information. B1_Building is the main BLOCK of the model as it represents the main processes that rule the behavior and structure of the building. Table 1. Main input model variables. B1_compensation encapsulates the processes necessary to deliver the energy consumed by the building Variable Description and to neutralize the environmental impacts (through the process of energy generation, for example, This file contains the description of the climate that affects the building. In with*.epw solar file photovoltaic or CO2 gas absorption systems). (climate file) this case, the building is located in Madrid, Spain. B1_WasteTreatment represents the processes related to waste disposal. Each of the different blocks *.idf file (model file) This file contains the structure of the building (geometry, materials, etc.). of the model is decomposed into a single process. Materials and constructing Needed for the calculations and is obtained using a dedicated database or The main variables that the model uses are detailed in Table 1. The BIM model is represented solutions database connected to external databases like the one provided by the ITeC [42]. by the Energy+ format, idf files, and climatic information is represented on the andepw files. Several other factors (variables) can be modified in the model to define the scenarios to be executed. The main output variables are shown in Table 2 and represent only a few subsets of the information obtained from the model is stored a text file following an XML format. Tablethat 1. Main input in model variables. Variable

Table 2. Main output variables. Description

Variable Description This file contains the description of the climate that affects the building. *.epw file (climate file) In this case, themodel building located in Madrid, Spain. the building’s The energy demand of the willisbe determined to minimize Energy Impact energy (energy for heating and cooling). *.idf file (model file) This file contains the structure of the building (geometry, materials, etc.). Environmental Analysis of the environmental impact of materials used (Global Warming, Ozone Materials and constructing Needed for the calculations and is obtained using a dedicated database or Impact Depletion, etc.) according to an LCA (Life Cycle Assesment). solutions database connected to external databases like the one provided by the ITeC [42].

The main output variables are shown in Table 2 and represent only a few subsets of the information obtained from the model that is stored in a text file following an XML format.


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Table 2. Main output variables. Variable Energy Impact Sustainability 2017, 9, 1004

Description The energy demand of the model will be determined to minimize the building’s energy (energy for heating and cooling).

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Analysis of the environmental impact of materials used (Global Warming, Environmental Impact Analysis of the economic costs of the LCA process, the materials used in construction, Ozone Depletion, etc.) according to an LCA (Life Cycle Assesment). Economic Impact and the energy and material demand of the prototype (described in the standard prEN Analysis of the economic costs of the LCA process, the materials used in 15643-4 [43]). Economic ImpactAnalysisconstruction, and the of energy and material demand ofenvironment the prototype(impacts of the social impacts the building on its immediate Social Impact (described in the standard prEN 15643-4 [43]). can be positive or negative) Analysis of the social impacts of the building on its immediate environment Social Impact (impacts can that be positive or negative) An example of the SDL PROCESS rules the model behavior (Figure 4) shows the behavior

for the DESIGNED state of the P1_Building PROCESS. This is the process responsible for the representation of the the SDL entirePROCESS life of the building, design phase to the destruction An example of that rulesfrom the the model behavior (Figure 4) showsand the recycling behavior for phases. In this case, the building starts in the DESIGNED state, representing the fact that a specific the DESIGNED state of the P1_Building PROCESS. This is the process responsible for the representation design has been selected for the building and the building process can begin. The BUILD state of the entire life of the building, from the design phase to the destruction and recycling phases. In this represents the fact that the building has been constructed and can be used. The USED state represents case, the building starts in the DESIGNED state, representing the fact that a specific design has been the fact that the useful life of the building is over and it needs to be demolished. Finally, the selected for the building and the building process can begin. The BUILD state represents the fact that DESTROYED state represents the fact that the building has been demolished. Every one of these the building has been constructed and can be used. The USED state represents the fact that the useful states has its own calculations and logistics; some of them using external calculus engines in a colife of the building is over and it needs to be demolished. Finally, the DESTROYED state represents simulation scenario. the fact that the building been demolished. oneand of these states has its own calculations The standard ISOhas 14040 was adopted forEvery the LCA impact method analysis. Specifically, and logistics; some of them using external calculus engines in a co-simulation scenario. impact method ECO 99 [44] was used.

Figure Behaviorof ofthe the building building in state. Figure 4.4.Behavior inthe theDESIGNED DESIGNED state.

Auxiliary variables defined in DCL allowed us to represent the parametrizations for a house in an experiment, which helps in defining the experimental design. The main model elements are represented in PROCESS diagrams; PROCEDURES are used to calculate the building energy


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The standard ISO 14040 was adopted for the LCA and impact method analysis. Specifically, impact method ECO 99 [44] was used. Auxiliary variables defined in DCL allowed us to represent the parametrizations for a house in an experiment, which helps in defining the experimental design. The main model elements Sustainability 2017, 9, 1004 8 ofare 17 represented in PROCESS diagrams; PROCEDURES are used to calculate the building energy consumed consumed of the can analyze anddifferent optimizeHVAC different HVACbased systems based onand the (this part of(this the part model can model analyze and optimize systems on the COP 2 energy COP and the performance of each active climate machine where know2 energy the kWh/m the performance of each active climate machine where we know the we kWh/m consumption consumption required to reach the thermal comfort forstudied). each situation studied). the model is required to reach the thermal comfort for each situation Once the model Once is correct, the final correct, the final users can only modify the DCL’s of theamodel by using a cloud infrastructure. users can only modify the DCL’s of the model by using cloud infrastructure. We can analyze the behavior of the PROCEDURES (that use a database to calculate the environmental, aspects of of thethe materials used), and and the systems applied to build environmental, social, social,and andeconomic economic aspects materials used), the systems applied to the The The S1_ACV-Materials PROCEDURE analyzes thethe environmental buildmodel. the model. S1_ACV-Materials PROCEDURE analyzes environmentalimpacts impactsand and the economic and social costs related to materials. The The S1_ConstructionProcess S1_ConstructionProcess PROCEDURE analyzes the construction process, as seen in Figure 5.

Figure Figure 5. This This figure figure details the S1_ACV_Materials and S1_ConstructionProcess.

One can connect, connect,thanks thankstotothe theSDL SDLmodularity, modularity, several buildings to define an urban In One can several buildings to define an urban area.area. In this this the model to define the communication mechanisms to be (on used the model case,case, the model only only needsneeds to define the communication mechanisms to be used the(on model itself). itself). The execution of the model that contains several buildings provides information of an urban The execution of the model that contains several buildings provides information of an urban area, area, instead of providing information of just a single isolated building. instead of providing information of just a single isolated building. Co-simulation techniquescan canbebe applied PROCEDURES to calculate the energy impacts Co-simulation techniques applied on on PROCEDURES to calculate the energy impacts using using state-of-the-art calculus engines like Energy+ [45]. Heuristic optimization is used, based on Hill state-of-the-art calculus engines like Energy+ [45]. Heuristic optimization is used, based on Hill Climbing, Simulated Annealing, or NSGAII algorithms. These optimization techniques allow Climbing, Simulated Annealing, or NSGAII algorithms. These optimization techniques allow the the dramatic dramatic reduction reduction of of the the number number of of scenarios scenarios to to be be executed, executed, whilst whilst still still obtaining obtaining aa good good answer. answer. The time needed neededtotoobtain obtainanananswer answer experimental design be large, as suggested in who [46] The time forfor anan experimental design cancan be large, as suggested in [46] who presented an example an execution of aexperiment real experiment in a distributed scenario. The criteria presented an example of an of execution of a real in a distributed scenario. The criteria used used was based on an expression that combined the different variables that were interesting in the was based on an expression that combined the different variables that were interesting in the definition definition the expression LCA. This was expression defined user inwe theused software we section), used (seewhich next of the LCA.ofThis definedwas by the user inby thethe software (see next section), which defined the experimental how it was executed. defined the experimental design and howdesign it was and executed. 4. 4. Results Results The and C The model model was was implemented implementedusing usingSDLPS SDLPSsoftware software[47,48]. [47,48].SDLPS SDLPSwas wasbuilt builtusing usingC++ C++ and languages. The model code (written in C for the tasks and procedures of the SDL blocks) was used C languages. The model code (written in C for the tasks and procedures of the SDL blocks) was ® through a Dynamic LinkLink Library (DLL). TheThe model was defined used through a Dynamic Library (DLL). model was defineddirectly directlyusing usingMicrosoft Microsoft Visio Visio®,, following SDLPS understands understands this following the the standard standard implemented implemented on on the the 2013 2013 version version as as SDLPS this format format and and transforms XML format format that that represents represents the the SDL SDL model. model. This transforms it it to to an an XML This coding coding implies implies that that the the model model can validated and verified by by reviewing reviewing the the graphic graphic diagrams diagrams in in Microsoft Microsoft Visio Visio®® .. This can be be validated and verified This property property dramatically simplifies the interaction between the different actors involved in the project. dramatically simplifies the interaction between the different actors involved in the project. Figure Figure 66 shows with aa model model for for aa building. building. shows the the SDLPS SDLPS loaded loaded with

Sustainability 2017, 9, 1004 Sustainability 2017, 9, 1004 Sustainability 2017, 9, 1004

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Figure 6. SDLPS interface with the building model. Figure Figure6.6.SDLPS SDLPSinterface interfacewith withthe thebuilding buildingmodel. model.

5. Executing on the Cloud: NECADA 5.5.Executing Executingon onthe theCloud: Cloud: NECADA NECADA The model was defined using SDL and all team members were aware of the hypotheses used in The was defined using SDL and all allteam teammembers wereaware aware ofthe thehypotheses used Themodel model wastype and were used in it. However, in this of model, parametrization ismembers a key element that of needs tohypotheses be reviewed to in it. However, in this type of model, parametrization is a key element needs to be reviewed to it. However, in this type of model, parametrization is a key element that be reviewed to carefully assure that the data introduced are accurate and correct. Additionally, once the developing carefully the data are Additionally, once the developing carefully assurethat thatthe thevalidity dataintroduced introduced areaccurate accurate andcorrect. correct. Additionally, onceno the developing team has assure agreed on of the model (in some and sense the model is accredited), modification team has agreed on the validity of the model (in some sense the model is accredited), no modification team has agreed on the validity of the model (in some sense the model is accredited), no modification is needed until the underlying hypotheses are modified. In that case, the parametrization proposed is until the hypotheses In case, parametrization proposed isneeded needed until theunderlying underlying hypotheses aremodified. modified. Inthat that case,the the parametrization proposed on the SDL diagrams trough the DCL’s is are the key element in defining the different scenarios to be on diagrams trough key element in defining the to onthe theSDL SDLThis diagrams trough the the DCL’s DCL’s isthe theby key element inteams defining the different scenarios tobe be conducted. parametrization can be is done third party who dodifferent not havescenarios to be directly conducted. This parametrization can be done by third party teams who do not have to be directly conducted. This parametrization done by third party teams who do not have to be directly connected with the model development. connected connectedwith withthe themodel modeldevelopment. development. 5.1. Description of the Current Platform 5.1. 5.1.Description Descriptionofofthe theCurrent CurrentPlatform Platform To simplify parametrization and error reduction, a Cloud service named NECADA® was ® was To parametrization and reduction, aa Cloud NECADA ® was To simplify simplify parametrization and error error reduction, Cloud service named NECADA developed to allow model parametrization and execution. Figure 7service showsnamed the login screen of the developed to allow model parametrization and execution. Figure 7 shows the login screen of the developed to allow model parametrization and execution. Figure 7 shows the login screen of the NECADA cloud solution. NECADA cloud solution. NECADA cloud solution.

Figure 7. NECADA cloud solution login screen. Figure 7. NECADA cloud solution login screen. Figure 7. NECADA cloud solution login screen.

NECADA manages the parametrization of the experimental design to be executed and sends it to SDLPS, which executes the LCA building model. SDLPS acts as a simulation server executing the experiments defined over the web; Figure 8 shows the public projects of the NECADA website. Each one of these projects owns specific building models (the building geometry), based on the Sustainability 2017, 9, 1004 [49], materials, constructing solution, weathers, and orientations that can be 10 of 17 BIM methodology permutated on the experiments. These permutations are the key elements that are defined by the analyst since it defines the space to be explored by the model (Figure 9). NECADA manages the parametrization ofSDL the experimental design be executed and sends it With this information—and based on the model that defines theto LCA of a building—the to SDLPS, which executes the LCA building model. SDLPS acts as a simulation server executing LCA could be calculated for the different scenarios. This allowed us to obtain the Pareto frontier, the experiments defined the variables web; Figure shows10the of the NECADA depending on the over selected (see8Figure to public review projects the file that contained the website. indicators Eachinone these projects owns specific building models (the building geometry), based used the of analysis). These indicators were defined formally on the SDL model and filled with the on correct values using [49], the database the modeler used on the specific project.and orientations that can be the BIM methodology materials, constructing solution, weathers, In Figure the results obtained NECADA are for the the e(CO) building that are shown [50]. The permutated on the11,experiments. These from permutations key elements are defined by the Pareto frontier represented in the upper left area of the figure, allowed us to determine the best fit analyst since it defines the space to be explored by the model (Figure 9). among all the possible alternatives in the model.

Figure 8. Public projectsshown shownon onthe the NECADA NECADA website thethe BRGF, MARIE, andand (e)CO Figure 8. Public projects websiteinclude include BRGF, MARIE, (e)CO projects. By using NECADA, users do not interact directly with SDL model, with projects. By using NECADA, the the users do not interact directly with thethe SDL model, butbut with thethe factors factors (declarations) used to parametrize the different experiments. (declarations) used inside theinside modelthe tomodel parametrize the different experiments. Sustainability 2017, 9, 1004

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Figure 9. File containing the permutations to be executed and those defined in the experimental design. Figure 9. File containing the permutations to be executed and those defined in the experimental design.


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With this information—and based on the SDL model that defines the LCA of a building—the LCA could be calculated for the different scenarios. This allowed us to obtain the Pareto frontier, depending on the selected variables (see Figure 10 to review the file that contained the indicators used in the analysis). These indicators were defined formally on the SDL model and filled with the correct values using the database the modeler used on thetospecific project. Figure 9. File containing the permutations be executed and those defined in the experimental design.

Figure 10. 10. Indicators to be used on the calculus of the LCA; not all all the the indicators indicators are are used used in in this this Figure specific specific example. example.

In Figure 11, the results obtained from NECADA for the e(CO) building are shown [50]. The Pareto frontier represented in the upper left area of the figure, allowed us to determine the best fit among all Sustainability 2017, 9, 1004 12 of 17 the possible alternatives in the model.

Figure 11. Results from the analysis of the different scenario for the e(CO) building. On top are shown the Pareto frontiers for the more than 4000 different parametrizations analyzed, on the bottom is a Figure 11. Results from the analysis of the different scenario for the e(CO) building. On top are shown sensitivity analysis obtained from a detailed analysis of all the obtained information. This helps in the the Pareto frontiers for the more than 4000 different parametrizations analyzed, on the bottom is a determination of optimal actions to save energy using the passive elements in the building. sensitivity analysis obtained from a detailed analysis of all the obtained information. This helps in the determination of optimal actions to save energy using the passive elements in the building.

Detailed results obtained on the (e)CO project can be found in [40]. Thanks to this holistic solution, the e(CO) building LCA can be improved in its design phase. NECADA simplified the interaction of the non-specialists in the simulation user-group with an SDL model that only needed


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Detailed results obtained on the (e)CO project can be found in [40]. Thanks to this holistic solution, the e(CO) building LCA can be improved in its design phase. NECADA simplified the interaction of the non-specialists in the simulation user-group with an SDL model that only needed to parametrize the different factors that must be introduced in each experiment. Through the use of SDL, we could go further in our analysis. During the use of the building, we could take advantage of the different sensors the houses currently had, from the real-time analysis of energy consumption to the possibility of controlling the windows. Since a model that defines the optimum solution for an LCA is mainly focused on the planning phase, some deviations and corrections must be performed during the use phase of the building. Here, a Smart Home connected through SDL can achieve its full potential. 5.2. A Smart House Connected through SDL and IoT In the “use” phase (Figure 3), we focused on how people were using the houses and how energy was managed. A Smart Home is usually seen as a house where almost everything can be controlled, including the windows, doors, temperature, etc. The concept of smart home was connected through the Cradle to Cradle metaphor to the sustainability concept. The interconnection of different hardware and software used to control a house makes it difficult to easily extend and reuse the solutions. Plenty of different alternatives currently exist, some of them based on standards like KNX [51,52], standardized on EN 50090, ISO/IEC 14543, or BACnet [53], an ASHRAE, ANSI, and ISO 16484-5 standard protocol, as well as others used as de facto standards like Modbus, a serial communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). There are also many other alternatives like LonWorks, Home automation, BACnet, DOLLx8, EnOcean INSTEON, Z-Wave, Intelligent building, Lighting control system, OpenTherm, Room automation, Smart Environments, and Touch panel. In this scenario, with several communication protocols interacting with several devices, the use of an abstract layer that helps in the definition and formalization of the several processes that must be considered in a smart home, or as an extension of this in a smart city, is necessary. Additionally, as shown in this paper, SDL can be used to represent the LCA of a building, becoming an interesting candidate to represent all the processes related to a building life from the planning phase to the day to day use of the different devices interacting in a home; therefore, giving information to the residents regarding the deviations detected from the original planning. For a detailed description of the proposed use of SDL in the frame of IoT, [54] can be consulted. 6. Discussion The proposed methodology has been successfully used in several projects. To design a double active façade [55], we used the model (in combination with Computational Fluid Dynamics (CFD) models) in a co-simulation approach. In the European project MARIE [56–58], we used the model to perform a double analysis for the residential typologies in the Mediterranean area, first by optimizing the comfort and economic criteria based on passive measures and, second, by a cost-effective analysis selecting active energy efficiency measures. Other projects where this model has been used include the ACE project described in [59], where the model was used to simulate the behavior of the different typologies that were later implemented in the project. The model, using different calculus engines, allowed the optimization of the analyzed system following the European normative CEN/TC 350 (UNE-EN 15643-2, UNE-EN 15643-3, UNE-EN 15643-4). The co-simulation approach made it possible to change the calculus engine to be used, for example, in the MARIE project, we used Trnsys® [60] while in others we used Energy+ [45]. Hence, the model could be used for normative purposes and to obtain green certification for new or refurbished buildings. The proposed methodology allowed us to define the model using a holistic approach and simplify the interaction between the different specialists. By using an infrastructure that understood this formal

following the European normative CEN/TC 350 (UNE-EN 15643-2, UNE-EN 15643-3, UNE-EN 156434). The co-simulation approach made it possible to change the calculus engine to be used, for example, in the MARIE project, we used Trnsys® [60] while in others we used Energy+ [45]. Hence, the model could be used for normative purposes and to obtain green certification for new or refurbished buildings. Sustainability 2017, 9, 1004 13 of 17 The proposed methodology allowed us to define the model using a holistic approach and simplify the interaction between the different specialists. By using an infrastructure that understood language, specific implementation was performed the projects, thus simplifying the verification this formalno language, no specific implementation wason performed on the projects, thus simplifying the process required for the simulation projects. The steps depicted in red in the simplified version of the verification process required for the simulation projects. The steps depicted in red in the simplified modeling presented by [41], are those 12. see Figure 12. version ofprocess the modeling process presented by that [41],are areimproved, those that see are Figure improved,

Figure 12. 12. Simplified Simplified version version of of the the modeling modeling process, process, based based on on [41]. [41]. The The SDL SDL executable executable model model can can Figure be validated validatedbyby all team members; furthermore, the automatic implementation assures its be all team members; furthermore, the automatic implementation assures its verifiability. verifiability.

7. Conclusions 7. Conclusions In this paper, the use of SDL to represent the LCA of a building holistically was introduced. In this paper, of SDL to represent thethe LCA of a building holistically was introduced. We presented howthe thisuse methodology simplified validation and verification problems relatedWe to presented how this methodology simplified the validation and verification problems related to this this type of complex model. It was also shown that the implementation of these models could be type of complex It was also shown that the implementation these could and be achieved achieved using amodel. desktop program that implemented SDL modelsof(in our models case SDLPS) a cloud using a desktop program that implemented SDL models (in our case SDLPS) and a cloud infrastructure that used SDLPS as a simulation server to offer a cloud solution. This cloud solution infrastructure used SDLPSprocess as a simulation serverThe to offer a cloud solution. This cloud simplified the that parametrization of a building. use of a standard language, suchsolution as SDL, simplified the parametrization process of a building. The use of a standard language, such SDL, simplified implementation; as several other tools understand SDL, as mentioned in [61–63], as among many others, this made the definition of the model and the final implementation independent of the chosen infrastructure. Model validation was performed with the SDL representation of the model, so that all project members involved could participate in the validation process. Verification was assured as the tool recognizes SDL diagrams; however, other validation techniques could also be applied (black box, white box, Turing test, etc.). From the perspective of the language proposed (one can select to follow this methodology with other formal languages like DEVS or PetriNets among others), SDL could be used not only to model the LCA of a building, but could naturally also represent the existing communications between the different sensors available in a building [54]. This can complete the vision of the building allowing models to be used not only at design phase, but also in the operative phase, thus becoming a virtual advisor for a house or urban area. Author Contributions: Pau Fonseca i Casas and Antoni Fonseca i Casas conceived the use of SDL in this study and adapted, designed, and implemented the methodology and the tools described here. The work was based on a simulator named SDLPS, developed initially by Pau in his Ph.D., that executed the model developed in Antoni’s Ph.D. Conflicts of Interest: The authors declare no conflict of interest.


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Abbreviations The following abbreviations are used in this manuscript: ANSI ASHRAE BRGF (e)CO ISO LCA SDL

American National Standards Institute American Society of Heating, Refrigerating, and Air-Conditioning Engineer Biblioteca Sector Gabriel Ferraté Equilibrium through Cooperation International Organization for Standardization Life Cycle Assesment Specification and Description Language

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