Preprint accepted at CISBAT 2021 - Carbon Neutral Cities - Energy Eﬃciency & Renewables
in the Digital Era, EPFL, Lausanne, Switzerland, 8-10 September 2021
The Internet-of-Buildings (IoB) – Digital twin
convergence of wearable and IoT data with GIS/BIM
Clayton Miller1,∗, Mahmoud Abdelrahman1, Adrian Chong1, Filip
Biljecki2,3, Matias Quintana1, Mario Frei1, Michael Chew1, Daniel
1Dept. of the Built Environment, National University of Singapore (NUS), Singapore
2Dept. of Architecture, National University of Singapore (NUS), Singapore
3Dept. of Real Estate, National University of Singapore (NUS), Singapore
Abstract. Internet-of-Things (IoT) devices in buildings and wearable technologies for
occupants are quickly becoming widespread. These technologies provide copious amounts of
high-quality temporal data pertaining to indoor and outdoor environmental quality, comfort,
and energy consumption. However, a barrier to their use in many applications is the lack of
spatial context in the built environment. Adding Building Information Models (BIM) and
Geographic Information Systems (GIS) to these temporal sources unleashes potential. We
call this data convergence the Internet-of-Buildings or IoB. In this paper, a digital twin case
study of data intersection from various systems is outlined. Initial insights are discussed for an
experiment with 17 participants that focused on the collection of occupant subjective feedback
to characterize indoor comfort. The results illustrate the ability to capture data from wearables
in the context of a BIM data environment.
The Internet-of-Things (IoT) paradigm has driven the deployment of a vast array of sensors
and devices that are designed to improve the performance of buildings. There are several key
challenges that IoT networks are meant to address. For example, there is a 50:50 chance of an
occupant being comfortable in a building according to a survey of 52,980 occupants in 351 oﬃce
buildings, which found that 50% were dissatisﬁed with their indoor environment . From the
operations and maintenance side, likely, 16% of the energy used in the building could easily be
saved using no and low-cost optimization and commissioning . In addition to IoT, professionals
in the built environment, such as architects, engineers, and urban planners, have also been
digitizing spatial data at a rapid pace through the use of 3D virtual information tools such
as building and city information and energy modeling (GIS/BIM/BEM) , and a signiﬁcant
amount of eﬀort is going into determining uses in the operations phase .
This paper focuses on the creation of a data aggregation platform to test how Internet-of-
Things (IoT) and wearable technologies can be better converged with Building Information
Models (BIM) and Geographic Information Systems (GIS). Developing and training Artiﬁcial
Intelligence (AI) models to make predictions based on these data can have an impact on
occupancy detection, energy systems optimization, and human comfort and wellness [5, 6, 7].
This process is done through the development of the Internet-of-Buildings (IoB) data convergence
platform on the campus of the National University of Singapore (NUS). These technologies
demonstrate the value of synthesizing data from numerous sources and creating interfaces that
enable building operations professionals to make decisions. This work attempts to meet the
deﬁciencies in previous literature  through the synthesis of data from dynamic IoT sources
such as wearables into GIS and BIM environments.
2. The Internet-of-Buildings (IoB)
The focus of this research is the development and testing of a data convergence platform. Figure
1 illustrates this new paradigm and the potential capabilities within various use case scenarios.
First, data connectivity is enhanced with the introduction of 5G capabilities indoors and outdoor,
increasing the bandwidth and reducing data exchange latency. Next, the maintainability of
buildings is improved due to the use of AI-driven drones that can scan buildings for maintenance
issues using the BIM/GIS models as a context. In universities, using the building as a teaching
test-bed is enhanced using spatial and temporal data convergence through wearable and mobile
augmented and virtual reality devices (AR/VR). Energy systems and digital twin building energy
models are calibrated using high-resolution occupancy data, resulting in the optimization of
climate control and lighting systems . Indoor and outdoor wellness and thermal comfort
is enhanced using data collected from multiple sources and used to inform and even modify
energy consumption behavior to achieve conservation targets. Energy behavior is collected by
synthesizing occupant information with smart meter data and social and behavioral intervention
methods that are tested in a ﬁeld setting. Wellness, productivity, and space utilization are
evaluated at the zone level, and people can be given recommendations about the zones that
would result in the most comfortable and productive experience for them. A key feature for tying
together the IoT/wearable and spatial domain is the ability to locate where a person or device
Data Connectivity 4G/5G/Wifi for Smart
Safety, and Project
5G, Drones, and BIM for Maintainability,
Decision-support, and Safety analysis
Smart Devices,Wearable IoT and AR/VR for
education of students
BMS/Smart Meter, PV Meters and BIM/BEM
integration to optimize control and find system
Indoor and Outdoor
Smart Devices, Indoor and Outdoor
IoT and Wearable IoT for Subjective
Indoor and Outdoor
GPS enhanced with GIS, BIM, and WiFi and
Bluetooth localization and occupant detection
IoT Contextual Pairing technologies
supplement security and privacy
The Internet-of-Buildings (IoB) Framework
4G and 5G
and Digital Twin Building
Energy Model (BEM)
Figure 1: The deployment of IoT in the built environment combined with spatial and human
data sources creates the IoB Framework.
in the building context beyond the accuracy that GPS can achieve. This situation requires the
use of indoor localization technologies such as those powered by Bluetooth. Security is enhanced
through contextual pairing with other sensors that add more layers to the authentication
process for digital access control systems. Finally, privacy is improved as the access to personal
information for IoB is not controlled in a centralized way; smartphones and wearable IoT owners
are able to choose what information is shared through the application interface.
3. Case study deployment
The case study implementation in this paper focuses on the aggregation and synthesis of data
from sensors located at various parts of the NUS campus, including the SDE4 building, a 5G-
enabled, net-zero energy building. Figure 2 illustrates the various data sources that have been
converged or are in progress of being connected. The ﬁrst pillar focuses on the collection of
data from humans through wearable devices, an example of which is when smartwatches were
deployed to collect physiological and subjective feedback data from building occupants .
The following two pillars fall within the category of 5G-connected devices such as smartphones,
robots, and drones . The next pillar focuses on collecting spatial information from occupants
and objects using an indoor localization system based on Bluetooth beacons deployed across the
test case buildings. This spatial information is then converged with a digital twin of the building
extracted from the BIM. The last two pillars focus on the data convergence of ﬁxed smart sensors
from indoor (building-scale) and outdoor (urban-scale) environments. These are sensors, for
IoB Data Convergence with BIM/BEM/GIS using a Spatially-aware Time-Series Database
Wearable Data Dynamic 5G Connected
Fixed IoT Sensor
Figure 2: The development of the IoB platform focuses on the data convergence of data from
various projects and systems in terms of data sources (columns) and stages of data processing
and convergence (rows).
example, that measure environmental air quality and thermal conditions across campus. The
merging of these data sets is possible through a series of technologies from third parties such
as hardware devices, middleware servers, and event-driven lambda function services. Finally,
the data convergence occurs in a time-series database that indexes the various sources using the
3.1. Dynamic wearable data convergence with BIM
Figure 3 shows this methodology from an experiment that used the IoB to collect and converge
data related to comfort preferences . It shows the path of a human across the ﬂoor plan of
the SDE4 building at NUS (left). As the occupant traverses the space, IoB collects physiological
information such as heart rate and step count while using indoor localization to calculate the
proximity to various objects in the building. These dynamic relationships are calculated using
BIM convergence with the IoT and human-generated data. The illustration shows a ﬁsh-eye
view of the occupant (bottom center) and the indoor localization app being used to track the
path. Finally, the visualization shows a vector-based proximity diagram (right) that illustrates
the relationship of the human and the various spatial objects in a vector model .
3.2. Thermal comfort preference experiment
For six weeks in early 2021, an experiment was deployed in the SDE1, SDE2, and SDE4 buildings
with the use of the Cozie Fitbit smartwatch platform (https://github.com/cozie-app) to
collect subjective thermal preference feedback. This method builds upon previous work [12, 14],
but with adaptations to increase the number of ecological momentary assessment questions and
the diversity of spaces in the case study buildings. The test participants were asked about their
thermal preference, clothing level, and activity level on the Cozie watch-face several times per
day while they were in the case study buildings. Their responses were attached to the BIM
through a Bluetooth localization app that was also installed on their phone.
Figure 3: An example of the data convergence from BIM, IoT, BEM, and human-generated
data in the Internet-of-Buildings platform. A full animated demo is found at this link:
4. Results and discussion
Figure 4 shows the results of the experimental implementation. The top row of the ﬁgure
illustrates the data collected in the spatial context in three levels of the case study building.
The IoB platform facilitated the capture of physiological and subjective feedback data from a
smartwatch and connected it to the spatial context of the BIM environment. The charts in
the next two rows show an overview of the preliminary analysis of this data set towards the
characterization of thermal preference in these buildings.
The use of the IoB platform to merge the subjective feedback data with the spatial context
resulted in several key insights. Many of the zones were outdoor spaces, and the results show a
higher than usual number of prefer cooler feedback, especially from the male participants. The
point clouds developed in the various regions of the ﬂoor plan illustrate the potential hot spots
in which there could be causes of discomfort not captured by the temperature and humidity
sensors installed. These initial results set the foundation for further analysis in contextualizing
the feedback according to each point’s relationship with the objects around it. There was an
expected imbalance in the feedback, which can be investigated using techniques to enhance the
data set before prediction . There is further work planned that falls outside the scope of this
Figure 4: Data collected during experiments related to characterize diﬀerent parts of the spatial
context for thermal preference for three levels in the case study buildings (SDE1-4). The ﬂoor
plans of each level illustrate the locations of subjective data collection (top) while the histograms
(middle and bottom) show a breakdown of occupant feedback according to gender and clothing
levels. This ﬁgure is best viewed in color.
paper to use these data for modeling techniques that can predict which zones would best ﬁt the
preferences of individual occupants.
This paper outlines the creation and testing of a data convergence platform for IoT/wearable
and BIM/GIS data. This methodology converges data for this case study from indoor and
outdoor sensor networks and occupants using smartwatch and smartphone interfaces. These
data are combined with the BIM of the case study using a mapping process between the spatial
and temporal contexts. Data collected from a deployment with 17 experimental participants
focused on the collection of thermal comfort preference subjective feedback. The data from
this experiment were converged on the IoB platform in the BIM context and showed insight
into thermal comfort preference in diﬀerent spatial zones. The next phase is to train machine
learning models for occupant preference prediction in the spatial context provided by the BIM.
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