CITA BIM Gathering 2015, November 12th -13th 2015
Development of a Model View Definition for Environmental and
Energy Performance Assessment
Sérgio V. Pinheiro1, Edward Corry2, Paul Kenny3 and James O’Donnell4
School of Mechanical and Materials Engineering, School of Architecture and UCD Energy
Institute
University College Dublin, Dublin, Co. Dublin
2
E-mail: 1sergio.pinheiro@ucdconnect.ie
edward.corry@ucd.ie
3
4
paul.kenny@ucd.ie
james.odonnell@ucd.ie
Abstract – Very often, building managers face the challenge of having to operate a building
in the absence of the appropriate information about how it should function. This problem is
one of the many reasons why buildings operate inefficiently and tend to consume excessive
amounts of energy. Building Information Modelling (BIM) is an emerging technology which
addresses the management of information throughout the Building Life-Cycle (BLC). Industry
Foundation Classes (IFC) is a non-proprietary data model of BIM that enables effective data
integration over the BLC. IFC is a rich data model which may represent the entire building,
however most applications are interested in a subset of this model. Hence, it is necessary to
filter the information exchange between different applications and Model View Definitions
(MVD) is the methodology to define such subsets. This paper presents the development of a
MVD for environmental and energy performance assessment to support building managers
during operation.
Keywords – MVD, IFC, BIM, Environmental and Energy Assessment.
I INTRODUCTION
It is widely acknowledged by industry and research
organisations that buildings operate inefficiently [1].
They consume nearly 40% of the total primary energy
in the world and are responsible for around 30% of
the total global CO2 emissions [2]. Some studies also
show an expected increase of 50% in energy demand
in buildings between 2010 and 2050 in a business as
usual scenario. However, following an energy
efficient and low carbon pathways could lead to 25%
reduction in total energy use compared to business as
usual [3]. Reduction in energy consumption in the
building sector is vital to any long term strategies.
Legislation, environmental concerns, financial issues
also influence organisations to reduce their energy use
[4].
More than half of the current building stock is
expected to still be operational in 2050. Considering
the lifespan of buildings, actions cannot be limited to
tighter controls on new constructions [3]. Increasing
demand for building services and comfort levels,
together with the rise in time spent inside buildings,
assure the upward trend in energy demand will
continue into the future [5].
For most buildings, the majority of energy use is
in the operational phase and energy conservation
efforts have appropriately focused on reducing this
energy use through smarter design and improved
building technology [6].
Building Information Modelling (BIM) is an
advanced information technology that is becoming
widely adopted in the AEC/FM (Architecture,
Engineering, Construction and Facility Management)
industry. BIM is a process for managing the
information produced during the design stage
throughout the Building Life-Cycle (BLC), in a
common format, in order to enable the best and most
efficient use of the information [7]. The Industry
Foundation Classes (IFC) is the most widely adopted
common data format in the BIM environment.
IFC uses an object oriented description to ensure
consistent data exchange and interoperability
between several applications. It enables sharing of
properties of building elements to support decision
making in different stages of the BLC. Most modern
BIM authoring platforms support the import and/or
export of IFC model data. This flow of information is
critical for collaboration and interoperability because
it connects different downstream applications, such as
CITA BIM Gathering 2015, November 12th -13th 2015
facilities management, structural modelling and
performance analysis applications [7].
The IFC schema can be used to model all
building components, however most stakeholders and
their applications have an interest in a limited area
(subschema) of this complex schema. Hence, the
exchange of information between applications must
be tailored according to domain specific Model View
Definitions (MVD). Traditionally MVD was used to
define an exchange of IFC data that would meet the
end user’s need and implement methods of
exchanging data between software applications.
The MVD proposed for this paper contains the
exchange requirements necessary for environmental
and energy performance assessment. This exchange
of information should provide clear and consistent
information to building managers, to enable more
informed decisions. The final goal of this work is to
support the efforts of the building manager at
different stages of the BLC in the reduction of
building energy consumption, without compromising
environmental performance. This methodology also
supports the building manager to determine the most
effective building operation strategy. The following
section explains what a MVD is and how to define
one. Section III defines the exchange requirements
necessary to perform environmental and energy
assessment. These requirements are used in the
process to develop a MVD for performance
assessment, as described in Section IV. Finally,
Section V discusses the limitations encountered in the
process, while Section VI concludes the presented
work.
II BACKGROUND ON MODEL VIEW
DEFINITION
Building managers often face the issue of model
exchanges being incomplete or error prone due to the
lack of semantic definitions within IFC [8]. IFC is a
rich product modelling schema, offering multiple
ways to define objects, relations and attributes [8].
These different ways of defining the same data led to
the development of domain specific MVD to define
precisely how building model exchanges should be
expressed using IFC.
The first MVD developed by buildingSMART is
known as Coordination View. The main purpose of
this view is to allow sharing of building models
between the major disciplines of architecture,
structural engineering and building services
(mechanical) [9].
An MVD is considered a subschema of the IFC
specification. The purpose of this subschema is to
select and specify the appropriate information entities
from a schema, their attributes and rules that govern
their possible values for particular uses [10]. The
selected entities that define a MVD are a subset of all
those in the original IFC schema.
IFC Independent
Re-usable
MVD Specific
Scope of
a single
MVD
Concepts
Variable
Concept
Static
Concept 1
MVD Overview
Concept Diagrams
Variable
Concept
Static
Concept 2
Static
Concept 1
Static
Concept n
Static
Concept 2
Static
Concept n
Binding of IFC independent
concept into an IFC release
IFC Release Specific
MVD Overview
Scope of
a single
MVD
Concepts
Variable
Concept
Static
Concept x
Static
Concept y
Concept Diagrams
Variable
Concept
Static
Concept x
Static
Concept z
Static
Concept z
Additional documentation
Fig. 1: MVD format overview [23]
Static
Concept y
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The first step of the process in defining a MVD
is to identify the scope of the information exchange
between one or more stakeholders. For each set of
information, the functional requirements to be
exchanged are defined as Exchange Requirements
(ER). These ER are later structured into an
Information Delivery Manual (IDM) representing a
standardised methodology that provides a universal,
repeatable and verifiable method for creating
information exchange.
The ER defined in one or more IDMs is
organised into a set of information modules, named as
MVD Concepts. MVDs are usually represented
diagrammatically, as shown in Fig. 1. The ER share
the same IFC independent requirement definitions
format with MVD. This makes it easy to merge
several ERs (which define data exchange between
stakeholders) into one MVD (which defines data
exchange between software applications).
The development of MVDs follows guidelines
provided by buildingSMART International [11]. The
basic structure of a MVD includes a set of concepts,
which reference a specific IFC entity. Each concept
defines a graph of entities and attributes, with
constraints and parameters set for particular attributes
and instance types. Concepts are backed up by
templates to uniquely describe the components of a
MVD [12].
The format for MVD diagrams and
configuration is defined by an XML schema, known
as mvdXML. This schema makes extensive use of
two general ideas: Definitions and Configurations,
which combined create one MVD. Definitions
capture a range of concepts and represents them and
their relationship in the context of the diagram, while
Configurations capture how those concepts are used
in a specific case (Fig. 2).
Definition
Configuration ‘N’
Configuration #2
Configuration #1
Reduce Scope
Add rules / agreements
Fig. 2: The use of Definitions and Configurations
to create MVDs [11]
This type of representation allows one single
MVD to contain all the exchange requirements within
scope, with the advantage to choose which of them
are necessary to satisfy a particular business process
reducing the scope of it. Another approach to reduce
the scope of a MVD is the application of Business
Rules (BR).
For example, BR can be used to vary the result
of using an information model (e.g. IFC data model)
without having to change the model itself. They
provide flexibility for the model through the
application of different sets of rules to the same
information model. A practical example of a BR
might be: “the humidity of an office must be less than
70% and greater than 30%” [13]. In this form, when
applied to a concept, a logical assimilation is
associated with the manner in which the
attribute/property is created.
a) mvdXML Schema
mvdXML refers to an electronic format for
representing MVD. It is a generic structure that is
applied to the IFC data schema. According to [12],
this format serves several purposes:
- To support automated validation of IFC datasets
- To generate documentation for specific MVD
- To support software vendors providing filtering
of IFC data based on model views
- To limit the scope of IFC for particular business
process.
In order to provide consistent and a computerinterpretable definition of MVD, buildingSMART
International created the IfcDoc tool [14]. This tool is
based on the mvdXML schema which aligns to IFC
EXPRESS schema. The IfcDoc tool is used to
generate documentation of the IFC specification itself
and the baseline MVD concept templates. It allows it
to quickly expand the generic MVD concepts to cover
the specific requirements and business rules that are
introduced by a set of exchange requirements.
III EXCHANGE REQUIREMENTS FOR
ENVIRONMENTAL AND ENERGY
PERFORMANCE ANALYSIS
In recent years, the environmental and energy
performance of a building has emerged as an
important topic in the AEC/FM industry. The peak
load and electricity demand of buildings are
increasingly scrutinised in order to reduce fossil fuels
consumption and satisfy legislative requirements[15].
Tools such as Building Management Systems
(BMS) that control systems operating status and
Energy Management Systems (EMS) that display
energy consumption help building managers to safely
and efficiently operate the building. However, the
information provided by these tools is not as reliable
as it should be [4], thus an absence of structured
information in the provision of optimally performing
buildings is present during operation.
Ideally, building managers require a set of
performance specifications that represent building
performance. This type of information is created
during the design stage and is known as design intent.
The design intent contains all the performance
specifications of the building and serve as a baseline
for future performance assessment. New practices use
energy prediction modelling to check building
CITA BIM Gathering 2015, November 12th -13th 2015
Codes’
Requirements
START
PROCESS
Construction
Type Library
Owner
END
PROCESS
Create/Edit BIM
Model
Architect
ENERGY
MODELLER
Generate Model with
Space Boundaries
Automated Process
Performance
Specifications
Energy Modeller
MECHANICAL
ENGINEER
PROCESS
Measurement Indirect
Maintenance
Costs
Rules
Requirements Data
Utility
Costs
Review
Energy Simulation Model
Energy Simulation
Energy Modeller
Automated Process
HVAC design
Mechanical Engineer
HVAC Price Info
Cost Estimator
Quantity
Surveyor
OUTPUT
Price Weather
Database Data
Requirements
Owner
ARCHITECT
OWNER
REFERENCE
INPUT
Process Map
IFC/Prices
Quantity Surveyor
Process
Optimum
Performance Analysis
Quantity Surveyor
Quantity Surveyor
Legend
input/output
data exchange
IFC File
IFC File
IFC
Augmented
Simulation
Results File
Bill Of
Quantities
Optimum Building
Performance Report
Fig. 3: Collaborative process for information exchange between stakeholders to define optimum operation
performance efficiency, thus enabling building
managers to compare actual performance against
expected design intent.
The gathering of specific performance
specifications is a time consuming process for
building managers, where in many cases the
information requested was lost during the handover
process or was not well documented. Unavailable,
unreliable and inaccurate information is a major cause
for inefficient building operation [16].
Building operation requires managers to
understand a building’s function, defined as a
controlled environment for a predefined purpose [16].
For this reason, building function is of paramount
importance for most performance analysis and is
therefore a priority for building managers.
Existing tools and techniques for monitoring
building performance fail to demonstrate the
relationship between building function, energy
consumption and associated environment impact in a
manner that allows building managers to make
actionable decisions [4]. A new approach to solve this
problem is the integration of BIM with predictive
modelling tools such as EnergyPlus or with Building
Management Systems.
BIM supports building managers, providing
direct access to the information they require to make
more informed decisions. BIM enables collaborative
working processes (Fig. 3) and acts as the central data
repository from which all project stakeholders can
have access to the same information at the same time.
BIM can represent very large data sets, however, only
part of this data is applicable to performance analysis.
The choice of specific data from BIM focuses on two
main aspects of building performance: environmental
conditions and energy consumption.
a) Environmental Conditions
Maintaining constant thermal conditions during
operation is one of the main tasks facing building
managers. Even minor deviations from static comfort
levels may be stressful and affect an occupant’s
performance and safety. Furthermore, temperature
preferences can vary among individuals and there is
no temperature that can satisfy everyone. Adaptive
comfort models deal with the human behaviour taking
into consideration that people will generally change
their behaviour accordingly to the changes in the
thermal environmental.
Extensive laboratory and field data have been
collected, which provided the necessary statistical
data to define conditions that a specified percentage
of occupants will find thermally comfortable such as
Predicted Mean Vote (PMV) and Predicted
Percentage of Dissatisfied (PPD). According to [17],
there are six primary factors that must be addressed
when defining conditions for thermal comfort:
- Metabolic rate (M)
- Clothing insulation (clo)
- Air temperature (⁰C)
- Radiant temperature (⁰C)
- Air speed (m/s)
- Humidity (%)
CITA BIM Gathering 2015, November 12th -13th 2015
The failure to meet the recommended thermal
comfort levels can have negative consequences on
occupant productivity [18]. Since personnel costs
dominate all others related to building operation by
two orders of magnitude, a comfortable workplace is
of the utmost importance for the economic success of
companies [19].
Thermal comfort has a significant influence in
determining the energy consumption of a building’s
environmental system [20].
b) Energy Performance
Typically building managers expend a minimal
amount of time focusing on improving energy
consumption due to loss of data and fragmentation of
information [4]. Building manager’s requirements
consist of a set of control parameters that are used in
the operation strategy of the building. Usually these
parameters come from prescriptive code compliance,
energy performance guidelines, energy simulation
models and performance benchmarks.
The European Commission published in 2002,
the first Energy Performance of Buildings Directive
(EPBD) [21], with a further revision published in
2010. This Directive has the potential to be an
important instrument in motivating all EU member
states to achieve higher building energy performance.
The EPBD established a set of minimum
requirements to perform energy assessment in new
and existing buildings. However, energy performance
from a building manager perspective covers much
more information than the one established by EPBD,
such as:
- HVAC schematics, specifications and schedules
- Design intent
- Building Management Systems (BMS)
specifications
- Operational & Maintenance manuals
- BMS alarm records
- Building performance history, etc.
A complete list of the building manager
requirements are described in [4].
These requirements take into account the
general indoor climate conditions, in order to avoid
possible negative effects such as inadequate
ventilation, poor environmental conditions and
designated function. The grouping of these
requirements defines the Exchange Requirements
(ER) for environmental and energy performance
analysis. The requirements described above are the
minimum parameters, but analysis is not limited to
them.
Energy Performance
ER-1
ER-2
FP1
BR
FP2
FP1
BR
FP2
Environmental Performance
ER-1
ER-2
FP1
BR
FP2
FP1
BR
FP2
Owner
Combined MVD for Energy and Environmental
IFC
Model
BIM
MVD for Energy
MVD for Environmental
Partial IFC
model for
environmental
performance
Partial IFC
model for energy
performance
Building Life-Cycle
Design
Construction
Commissioning
Operation
ER
Exchange Requirement
FP1
Functional Part
BR
Business Rules
Fig. 4: Process of information exchange using the MVD methodology to support environmental and energy
assessment during operation
CITA BIM Gathering 2015, November 12th -13th 2015
During operation building managers suffer from
the lack of a specific set of performance requirements
to efficently operate buildings. A need to explicitly
capture the exchange requirements is the main
motivation for the development of a MVD for
performance assessment.
By doing so, building managers can easily
retrieve the required information to conduct their
analysis. This approach reduces the time that building
managers spend trying to find and extract the required
information. It also helps building managers to focus
on improving building performance reaching
optimum operation.
IV DEVELOPMENT OF THE MVD
The proposed MVD for assessment defines the
exchange requirements required by building
managers to assess operational performance. It
represents the information to be exchanged between
two or more stakeholders in support of a particular
business process at a specific stage of the BLC, as
shown in (Fig. 4). It is important to understand that
these requirements come from the end user’s need and
the primary role of the IFC model view is to ensure
IFC implementation supports these requirements.
The first step in the creation of a MVD is to map
the ER to IFC entities. This process requires a deep
knowledge of the IFC schema. The IFC
documentation, available in the buildingSMART
website [22] helps the mapping process. This
document contains the specification of the IFC
standard and consists of data schema, represented as
EXPRESS and XML schema specification, and
includes terms, concepts and data specification items
as defined by the AEC/FM industry.
After finishing the mapping process the next
step is to use the IfcDoc tool [14] to create the MVD
itself and generate its documentation. Previous
attempts at defining MVDs used templates to
generate the diagrams manually, but since IfcDoc was
Entity
Model View Definition
published all the documentation is automatically
generated by this tool. The documentation generated
is in HTML (HyperText Markup Language) format
and serves as the basis for vendors to implement
export and/or import functions in their software.
For instance, if a BIM software has already
implemented a MVD to support a specific business
process, the output IFC file will contain only the
exchange requirements defined for that particular
analysis reducing the amount of irrelevant
information. By providing building managers with
this type of clean information, they can now start to
focus on improving the efficiency of the building.
This approach, in theory, reduces the time necessary
to collect the information from the previous stage of
the BLC. A small demonstration of the creation of a
MVD is presented in the next section.
a) Demonstration
In order to reduce the level of complexity only one set
of exchange requirements is examined in this
demonstration: that relating to indoor air temperature.
Indoor air temperature is a key factor that needs to be
monitored inside a space in order to maintain
appropriate environmental conditions and is directly
related to the energy consumption due to the HVAC
and related systems. Spaces are occupied areas or
volumes that provide certain functions within a
building. The mapping of the exchange requirement
“space” to IFC specification is IfcSpace.
For this demonstration the IfcDoc tool is used to
create the instance diagrams of a MVD. As shown in
Fig. 5, the entity IfcSpace can be defined in different
MVDs (highlighted in yellow). For each MVD a set
of concepts (highlighted in green) are applied
according to the exchange requirement of a particular
process. Technically, concepts are independent of any
IFC Model View Definition, which makes it possible
to re-use the same concept even when the IFC model
specification changes.
Exchange Concepts
Instance Diagram
Fig. 5: Example of an instance diagram of the IfcSpace entity assigned to different MVDs containing several
MVD concepts
CITA BIM Gathering 2015, November 12th -13th 2015
This example is only one entity and the final
MVD for environmental and energy performance
assessment will contain all the exchange requirements
and their relationships. The main purpose of this
MVD is to support building managers to assess the
building during operation.
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V LIMITATIONS AND DISCUSSION
The IFC schema is the standard for information
exchanges in BIM. It is a rich model that addresses
the needs of different disciplines and provides a
variety of ways to define parts of a building. Hence
the use of model views to explicitly define IFC
implementation is required. One of the main issues
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VI CONCLUSIONS
This paper presented a methodology to support
building managers in specifying and analysing
building environmental and energy performance. The
idea behind this approach is to capture the building
manager requirements and address them using the
MVD methodology. This approach offers the
opportunity to export IFC files according to the
building manager’s requirements defined in the MVD
specific to performance analysis.
The MVD presented in this paper is still at an
early stage of development. A full demonstration of
the potential of this methodology is planned after the
completion of the MVD for environmental and
energy analysis. If the results from this test are as
expected, the MVD will be submitted to
buildingSMART International to become an official
MVD.
ACKNOWLEDGMENT
This work was supported by a Marie Curie FP7
Integration Grant within the 7th European Union
Framework Programme, project title SuPerB, project
number 631617 and Conselho Nacional de
Desenvolvimento Científico e Tecnológico (CNPq)
under the program Science Without Borders.
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