This article is a result of joint workshop which took place during Sustainable Places 2022 conference in Niece, France, and was co-organized by the Building Digital Twin Association (BDTA) and six EU-funded projects that have developed a construction-phase digital-twin data model, and their ontological representation, which is capable of capturing all data requirements for the digital representation of building and/or infrastructure construction sites. Four of the EU-funded projects participating in the event contribute to this Open Letter which aims to highlight the relevance of ontology in the digital twin environment, and the approach by the different EU-funded projects. All four LC-008-EEB funded projects contributing to this article (BIMprove, COGITO, ASHVIN and BIM2TWIN), agreed on joining forces for raising awareness around Digital Building Twins and its impact in the construction industry. Their primary aim is to share knowledge, experiences and research outcomes with other stakeholders and communities around the EU and beyond, via online communication like webinars, newsletters, social media channels and scientific or technical articles. This initiative aims at delivering the wide range of digital tools for the construction sector needed on the European market and to raise awareness about the benefits coming from their use.