Buildings account for about one-third of global energy consumption and one-quarter of CO2 emissions. Furthermore, lighting accounts for 20 to 30% of the energy demand in non-residential buildings. Integrated planning and control systems harness daylight potential, improve comfort and lighting quality, and take into account interactions with thermal performance. Simplified usage assumptions during the planning phase, combined with heterogeneous user preferences and high user dynamics, often result in implemented control systems deviating from their intended goals. Post-occupancy evaluations provide facility management with an opportunity to adapt control systems to actual usage patterns after commissioning. In practice, however, proprietary system architectures and a lack of transparency (due to the multitude of interfaces between design, construction, and operation) prevent the consistent implementation of integrated systems.

Building Information Modeling (BIM) is establishing itself as an interoperable, central information base (e.g., via IFC and gbXML) for analyses, simulations, and facility management applications; however, it still does not adequately represent control logic, sensor technology, and dynamic parameters. Digital twins (DT) extend BIM with bidirectional real-time data, enable monitoring, adaptive control, virtual and continuous commissioning, and help reduce performance gaps. This requires that control logic, topologies, and interfaces be modeled as a single source of truth. This is where the TwinLight research project comes in: it enables the development of control systems within BIM, links them to operational data via a bidirectional architecture, establishes open interfaces and organized collaboration, and facilitates data management and commissioning according to Open BIM principles using domain-specific languages and repositories. As a result, integrated lighting strategies become practical, transparent, and lifecycle-capable.

A project-based literature review of 57 relevant studies indicates that BIM must be expanded to include dynamic operational data, standardized interfaces for energy and daylight simulations, and end-to-end workflows from the model level to the implementation level. A lack of interoperability remains the main barrier. Lighting is significantly underrepresented in research and digital twin applications, while HVAC dominates. A complementary market study (165 usable responses) confirms that BIM is perceived as relevant and offers transparency and better collaboration, but often fails due to interface issues, interoperability problems, time constraints, and a lack of qualifications. User-related data is rarely collected, leaving potential for comfort and efficiency untapped. Small companies suffer from resource and expertise bottlenecks, while large companies struggle with interfaces and semantic inconsistencies. The studies identify Open BIM, modular systems, and phased implementations with clear roles and learning processes as recommended measures.

TwinLight specifically extends BIM with functions for modeling, parameterization, and automatic commissioning of building automation, thereby laying the foundation for digital twins. At its core is a graphical and textual domain-specific language (DSL) in Revit, complete with an add-in. Control components are placed via this DSL as Revit families with unique IDs and technical parameters, topologically connected, and made exportable as 2D schematics and dot graphs. In the BIM-based environment, control systems are thus configured, simulated, validated, optimized, and automatically transferred to the physical system. Integrated rules automatically check implementations for consistency. For model verification, IFC models are checked using rule-based semantic reasoning. This process generates traceable inspection reports, enabling errors to be caught before physical implementation. Runtime artifacts are generated via the DSL. An open, configurable middleware uses the enriched BIM model as a single source of truth, automatically generates configurations, connects to the physical control components, and implements bidirectional data flows. The middleware architecture includes, in particular, CQRS, a homogeneous JSON data model, InfluxDB for time series, and OAuth2. By feeding configurations generated from the model into the middleware and providing real-time feedback, the TwinLight system architecture enables the transition from BIM to DT, facilitating comprehensive evaluations, continuous system optimization, and cross-phase traceability among different stakeholders for control purposes. The system architecture was tested for the natural and artificial lighting systems. However, the generic design of the tools and workflows allows for extensibility to other systems.

To support the iterative development of the TwinLight system architecture and the evaluation of the workflows created, a Living Lab at the University of Innsbruck was utilized to test acceptance and energy efficiency under real-world conditions. The entire order-picking workflow (validation, artifact generation, and initialization) was tested in this real-world study setting. A TAM study (n=23) yielded generally positive evaluations, particularly for the Revit plugin and DT interaction; training improves perceived usability.

Project management

Zumtobel Lighting GmbH

Project or cooperation partners

• Hella Sun and Weather Protection Technology GmbH
• University of Innsbruck, Institute of Construction and Materials Science, Department of Energy Efficient Construction
• University of Innsbruck, Department of Computer Science

Zumtobel Lighting GmbH
Johannes Beiter
Schweizerstrasse 30
A-6850 Dornbirn
Tel.: +43 (664) 80892 3201
E-mail: johannes.beiter@zumtobelgroup.com
Web: https://www.zumtobel.com/com-de/index.html