With the entry into force of the Paris Climate Convention of the United Nations on 4 November 2016, the coun-tries of the world have set themselves the ambitious goal of limiting global warming to well below 2 degrees Celsius, or better still below 1.5 degrees Celsius compared with pre-industrial levels. If the states take this agree-ment seriously, there will be no way around comprehensive energy optimization and modernization of existing buildings in the coming years. On the one hand, such a development puts building owners under pressure to bring their real estate portfolios onto a corresponding lowering path as efficiently as possible. On the other hand, providers of climate-relevant real estate services will also have to further develop their offerings if they want to survive in the market. The guideline developed in this project is intended to support the relevant stakeholders (portfolio, asset, facility, sustainability, construction project managers, facility service providers, property managers, planners, contrac-tors, energy service companies, etc.) in these changes. The recommendations are aimed at profitable procurement practices for building owners and attractive value propositions from real estate service providers. All content is based on research literature and a large-scale empirical study (46 interviews and documents analysis).The guide contains recommendations on the following aspects:Strategy of Building Owner Organisations- Sustainability Strategy- Holistic economic efficiency assessments- Rethinking Procurement PracticesStrategy of Service Provider Organisations- Developping business models actively and with appropriate methods- Becoming partners for achieving strategically important outcomes- Proving economic viability of servicesTechnical Building Operation- Capturing the current condition of the building(s): digital data management, benchmarks, monitoring systems- Optimisation of operation: continuous commissioning, energy performance and energy supply contracting 2.0, remote monitoring and control / needs-based and predictive maintenance, automatised energy optimisationModernisation: - Multi-year planning and variant studies- Integrated offers and collaborations models- Systemactic commissioning