Responsibleproperty development, sustainable investing

Our mission

The term ‘assiduus’ means ‘constant, regular, perpetual’ in Latin, in other words what we today refer to as ‘sustainable.’ Sustainability is at the core of our corporate strategy, not only in terms of the environment but also when it comes to our social responsibility and approach to corporate governance.

Our impact investing strategy ensures financial returns and security of capital for our investors in all our property developments while also taking into account the impact on the environment, people and the community. As such, our comprehensive understanding of sustainability creates ethical added value for investors.

ESG (environmental, social and governance) is at the heart of our approach to office and urban multi-use city district developments for institutional investors who are pursuing a long-term strategy.

We stand for responsible business practices that benefit the environment, employees, occupiers and investors.

Robert-Christian Gierth & Alexander Happ

Portrait von Alexander Happ


Executive Director | PARTNER

Partner Image 2


Executive Director | PARTNER

The company

ASSIDUUS Development was founded in late 2019 by Robert-Christian Gierth, Alexander Happ and the Berlin-based IDEAL Versicherungsgruppe.

Executives Robert-Christian Gierth and Alexander Happ have years of expertise in the real estate sector and an extensive track record that includes site and location development as well as the realization of high-volume development projects.

You can download our acquisition profile here.

ASSIDUUS Developement is a member of:


Alexander Happ

Alexander Happ (born in 1968) became managing director of Berlin-based development company BUWOG Bauträger in 2012 and, following the company’s acquisition by Vonovia, headed the German development segment until late 2019.

After completing his apprenticeship in foreign trade and working in the export business in Hong Kong, Alexander Happ studied business engineering in Hamburg as well as economics and business administration in Kiel. He began his career in 1993 at property developer WOBAU Happ. Alexander Happ then joined Vivico Real Estate in 2000 as general project manager for the Europaviertel land use redevelopment in Frankfurt.

Prior to joining BUWOG in 2012, Alexander Happ acted as a member of the executive board at development company Interboden Innovative Lebenswelten based in Ratingen and as the managing director of Ideal Assets based in Düsseldorf/Cologne.

„Many market participants benefit from the attractiveness of such metropolitan regions like Berlin, although many people in the community simply feel left behind. It is something I have experienced throughout my career as a property developer and managing director working for a development company that is in the public spotlight. My personal motivation in founding ASSIDUUS is to be able to work more freely with a stronger focus on the community’s environmental and social well-being. I am convinced that investors will also benefit from the company’s emphasis on ethical standards in line with our ESG criteria.“

Robert-Christian Gierth

Robert-Christian Gierth, born in Berlin in 1963, is a trained real estate manager and holds a degree in valuation of developed and undeveloped land from the German Real Estate Academy (DIA Freiburg). He is also a member of the Committee of Land Valuation Experts (Gutachterausschuss für Grundstückswerte) in Berlin.

Robert-Christian Gierth established the Colliers International Berlin office and stayed on as managing partner until late 2019. During his 10 years with the company, he was key in making the company one of the leaders in commercial property in Berlin.

After completing his training as a real estate agent in Munich, Robert-Christian Gierth became director of office leasing at Müller International Immobilien (now BNP Real Estate).

He returned to his native city of Berlin after German reunification and founded real estate service provider CONECTA Immobilien, which he managed for 12 years.

Robert-Christian Gierth subsequently worked for state-owned developer Berlin-Adlershof where he was responsible for the development and sale of properties located at the science and technology park. He also worked as branch manager at INVESTA Projektentwicklung prior to joining Colliers International.

„The real estate sector needs to recognize its environmental responsibilities. Reduced carbon impact on construction and building operation is a goal that can only be achieved by implementing end-to-end concepts, not by buying certificates. ASSIDUUS develops ‘zero carbon’ properties using innovative resource optimization and consistent recycling practices. Because our future depends on it.“

„Maintaining the balance between profitability, environmental sustainability and the good of the community is key to ASSIDUUS’ approach to property development. I am convinced that investors will also benefit from our strategic focus on ESG criteria.“


„ASSIDUUS develops ‘zero carbon’ properties using innovative resource optimization and consistent recycling practices. Because all of our futures depend on it.“

Robert-Christian Gierth

Commitment to ESG

ASSIDUUS Development is committed to employing responsible business practices when it comes to the environment, the community and governance. That’s why ASSIDUUS is planning to introduce ESG scoring based on the GRESB standard and will implement the new EU taxonomy on sustainable investment in all of its projects.

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  • Reduced carbon impact on construction
  • Building material recycling (cradle-to-cradle)
  • ‘Zero-carbon‘ building operation that conserves resources (max. 100 kWh per sqm)
  • Minimizing energy and water consumption
  • Water re-use
  • Waste reduction and recycling

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  • Reduced rent for daycare facilities, community and cultural projects and displaced businesses
  • Space will not be let to ethically problematic companies with business models related to arms trade, child labor, wage dumping or exploitation of natural resources
  • Ethical and environmental reporting from potential tenants
  • Selecting service providers and suppliers that have the same ethical standards
  • Supporting social projects

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  • Transparency in communication with investors and government authorities
  • Involving communities in all aspects of project planning
  • Transparent reporting on planning and development activities
  • Innovative IT platform with connected project, calculation and controlling software
  • ‘Zero tolerance‘ of corruption and acceptance of undue advantages

Press contact


Nicole Lindner
Executive Assistant


02.09.2020: Christian Korak joins ASSIDUUS as new Commercial Director

The team continues to grow at Berlin-based property developer ASSIDUUS. The latest addition is new Commercial Director Christian Korak, a young analyst with international experience in corporate planning and property development.

You can download the complete news here.

06.08.2020: ESG keeps property developers and fund managers on their toes

ESG does not stop at fund managers like Hansainvest or property developers like ASSIDUUS. Concerns around sustainability and ESG criteria have become relevant for many market participants in the real estate sector. We are seeing increasing pressure from both the European Union and directly from the investment side.

You can read the complete article in german language here.

Source: Immobilien Zeitung

01.07.2020: ESG?! REAL sustainability - Heuer Dialog Digital Talk powered by ASSIDUUS & HANSAINVEST

ESG - Three letters that will have tremendous impact on the real estate sector. Demand for sustainable property development based on reliable ESG criteria continues to grow in the face of climate change and the ongoing expansion of our cities. ESG (environmental, social, good governance) criteria stand for a relationship to sustainability that not only guarantees secure returns for investors but also promotes environmental and social well-being as well as governance based on ethical standards. In this talk, Robert-Christian Gierth and Alexander Happ, Executive Directors of ASSIDUUS Development GmbH, together with Managing Director Ludger Wibbeke and Head of Compliance, AML & Sustainability Stefanie Kruse from HANSAINVEST Hanseatische Investment GmbH, explain why their companies are fully committed to ESG.

You can view the full webinar here.

12.06.2020: ASSIDUUS uses Reaforce software by Reasult BV

Reliable, efficient property development calls for the right software solution. ASSIDUUS relies on the Reaforce software solution by German/Dutch real estate software developer Reasult BV (Reasult) when it comes to managing its development projects.

You can download the complete news here.

21.04.2020: Newly launched property developer ASSIDUUS systematically applies ESG sustainability criteria to property development projects
  • Alexander Happ (formerly BUWOG/Vonovia), Robert-Christian Gierth (formerly Colliers International) and the Ideal Insurance Group found new property company
  • Sustainable and socially responsible property development based on ESG criteria
  • First project in Berlin district of Charlottenburg-Wilmersdorf

You can download the complete news here.

16.04.2020: ASSIDUUS launches new website
You will soon find more information about our new projects here.


Want to work at a company that offers exciting projects in wood and wood hybrid construction with a focus on zero carbon? A company with high ESG standards that relies on professional IT systems like Reaforce for calculation and corporate planning and Project Networld for project and document management?

You’ve come to the right place if you value mutual transparency, passion and a corporate culture based on mutual trust. Become a part of the Assiduus company spirit!

Please send your full application documents to


We look forward to hearing from you.

ASSIDUUS Development GmbH

Bleibtreustr. 34 10707 Berlin

+49 (0)30 403687400