About Annex 91

The BIM (Building Information Modelling) methodology is an approach for integrated digital planning that carries the potential for significant improvements in building energy performance. The method foresees that information from stakeholders like architects, planners, modellers, constructors and even facility managers feed into the same data source – the BIM model. In the planning phase the model thus becomes the information hub for geometric data, thermal parameter of building elements (walls, slabs, outer shell etc.), the building energy systems (heating, cooling, building automation) and much more. BIM comes in two flavors: closed BIM, which restricts cooperation to a limited set of software tools with little possibility to cooperate outside a given software environment; and open BIM, which is based on the internationally standardized IFC (Industry Foundation Classes) Schema (ISO 16739-1:2018) and allows to exchange modelling data between different software tools from various vendors. Along with IFC there are further open buildingSMART standards like BCF (BIM-Collaboration Format) and IDS (Information Delivery Specification) as well as IDM (Information Delivery Manual). This project will work with the open BIM methodology. 

This Annex project addresses the challenges that arise when advancing the technology and the processes, which constitute successful open BIM projects:

  1. A common library of BIM definitions to improve seamless data exchange between different software tools.
  2. Research on improving planning processes and development of guidelines for better collaboration.
  3. Gathering experience in use cases that apply the BIM methodology, including both planning and operation of buildings, with a special focus on thermal simulation. 

The Annex project aims at achieving the following main goals: 

  • Goal 1: Making energy efficiency assessment and optimization become an integral feature of open BIM 
  • Goal 2: Building the foundations for open BIM processes and data models that are beneficial especially for small and medium enterprises (SMEs) and which enable seamless cooperation of all stakeholders in a common open BIM project 
  • Goal 3: Advancing the interoperability and harmonization of open BIM processes and data models both on national and international level 

The main target audience for this Annex project are the stakeholders involved in planning, construction and operating buildings and districts: planners, architects, structural engineers, building physicists, construction companies, facilities managers, BIM managers, sustainability consultants and other expert disciplines.  

The challenge is to strengthen small and medium enterprises (SMEs) and enable them to participate in high-volume building projects with large stakeholders. The project shall reduce the technological barriers in large BIM projects, so that smaller companies can participate. Aside of the common open BIM library and the reference model, this may include the development of tools and guidelines localized to each country’s language (since the construction sector often operates locally), the definition of requirements for open BIM projects (like modelling guidelines and Exchange Information Requirements or IRs) and a register of service requirements for open BIM projects. 

The Operating Agent (OA) for this Annex is taken by Austria, represented by Dr. Gerhard Zucker from the AIT Austrian Institute of Technology GmbH. The subtask structure is as following:

  • Subtask 1: Dissemination, Communication and Reporting
  • Subtask 2: Use Cases 
  • Subtask 3: Open BIM Processes & Modelling Guidelines 
  • Subtask 4: Reconciliation of Ontologies Towards a Common BIM Library 

Planned deliverables are summarized in the following table.



Description (responsible subtask(s) in brackets)


Biannual Annex Status Report according to Annex Status Report template including material to be used in the EBC Annual Report (1)


Webpage for communication of Annex activities, outputs, and deliverables and internal area for exchange of documents / files amongst Annex participants (1)


Annex Fact Sheet describing the Annex, aims and intended products (1)

D4 Report on Subtask 2 “Open BIM Building Energy Performance and Building Operation Use Cases” targeting National and international standardization bodies, buildingSMART Domains and Chapters, construction trades and academia (2)
D5  Report on Subtask 3 “Open BIM Processes & Modelling Guidelines” targeting National and international standardization bodies, buildingSMART Domains and Chapters, construction trades and academia (3)

Report on Subtask 4 “Towards a Common BIM Library” targeting National and international standardization bodies, buildingSMART Domains and Chapters, construction trades and academia (4)



Educational material e.g., academic lectures (1)



Articles for EBC news incl. announcement on approval of this Annex project; progress, results, and events organized and completion of final report (1)


Final project report including project summary report, project results and policy recommendations (1)


The Annex results will be based on the activities (research projects, theses, studies) that were collected at the time of writing and are listed in the Appendix with further activities being added during the runtime of the Annex project. 

Annex 91 will last from 2024 to 2026. Jour Fixe will be held monthly, while plenary meetings and releasing ExCo reports will take place bi-annually.

Participants: Australia, Austria, Belgium, Brazil, Denmark, Germany, Italy, Ireland, Sweden, United Kingdom

Annex Info & Contact

Status: Ongoing (2023 - 2026)

Operating Agent

Gerhard Zucker
Digital Resilient Cities
Center for Energy
AIT Austrian Institute of Technology GmbH