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 Development 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.

Environment Icon



  • 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

Governance Icon



  • 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


Christian Korak

Christian Korak

Commercial Manager

Nicole Lindner

Nicole Lindner

Executive Assistant/
PR/ HR/ Marketing

Nils Noack

Nils Noack

Technical Manager



18.04.2021: How sustainable is the real estate industry? - Alexander Happ talks about it in the InterACT Insights Podcast

For Alexander Happ, the environment, social responsibility and good  governance are the core elements of its coporate strategy. His project development company ASSIDUUS – the Latin word means constant and perpetual – not only bears sustainability in its name, it also lives it: for example, through a strict focus on CO2-reduced construction or by awarding contracts only to service providers who follow social standards.

The experienced manager Alexander Happ still sees room for improvement in terms of sustainability in the real estate industry: "All actors – including investors – could benefit from greater responsibility for social, environmental and ethical concerns. This is because the demand for corresponding real estate projects is increasing." Alexander Happ discusses what to do and how the industry sees the topic in the current podcast  with moderator Alexander Heintze.

04.03.2021: ASSIDUUS becomes partner of Madaster - the new cadastre for materials

Madaster is a global online platform that significantly advances the circular use of products and materials in the real estate industry. This cadastre of building materials will provide comprehensive transparency on tangible assets. Product and material data can be stored, enriched, shared, and managed. This is how sustainability and value creation are brought together.

The basis of Madaster is an ever-growing ecosystem of partners, to which ASSIDUUS has joined.

"As a company that has made the ESG triad of ecology, social responsibility and good corporate governance the basis of its work, we have to face up to this task in all its complexity. We are convinced that Madaster is the right instrument to provide value to circular economics in the construction process and thereby to further advance it." Robert-Christian Gierth and Alexander Happ, Managing Director and Founder of ASSIDUUS Development

With the Madaster online platform, buildings become commodity banks and their material value in the sense of the circular economy can be clearly identified from the outset and thus incorporated into the overall calculation. In addition, it is possible to have an extensive material passport made for each building, in which information about the quality, origin and value of the installed materials is also recorded in the exact position in the building. This allows later targeted deconstruction and recycling process.

You can find out why we are part of Madaster Germany in our video message.

25.02.2021: Urban Real Estate Lab: Is working from home really a megatrend of today?

Four months ago, Alexander Happ and other experts already asked themselves this question . The expert panel has met again with the result: Working from home will continue to be part of office development in the future. The real megatrend, however, is digitalization!

You can view the video in german language here.

11.02.2021: Impact Investing – How important is the "S" in ESG - Heuer Dialog Digital Talk powered by ASSIDUUS

Alexander Happ and Robert-Christian Gierth discussed the topic of impact investing together with interesting speakers.

What we all agreed on: The S must be defined and manifested in order to create transparency for investors and project developers, but a clear "checklist" will not be sufficient. We at ASSIDUUS therefore work with the Best-in-Class approach with regard to the implementation of sustainability criteria.

You can view the webinar here.

13.01.2021: Clear ESG criteria for making decisions? Non-existent!

Sustainability is also becoming more important for real estate investors. However, there is still a lack of a standardized reporting structure that brings together key figures in a clear and comprehensible way. Robert-Christian Gierth and Ludger Wibekke, Hansainvest, have written an article about this topic.

You can read the complete article in german language here.

Source: Immobilienmanager Verlag IMV GmbH & Co. KG



17.12.2020: 2021 – Time to panic for the property market?

The roundtable event on topic "2021 - Time to panic for the property market?", hosted by REFIRE ( and Targa Communications (, was broadcast on 9 Dec 2020.

Despite the hopeful signs regarding the development of a vaccine, the chaos caused by Covid-19 is set to affect the global economy for the foreseeable future.

With the pandemic making it necessary for everyone to adapt the way in which they work, shop and socialise, the way in which we interact with each other in the built environment and utilise real estate has also changed. As a result, property markets have been impacted by the virus, with some sectors more vulnerable than others. What are the prospects for real estate investing in Germany for 2021?

Will the "new normal" bring opportunities or will it be a disaster for property investors, property and asset managers? Is it time to panic?

©Produced by Targa Communications

You can view the video here.

27.11.2020: Anyone involved in digitalization should go to Berlin

Robert-Christian Gierth took part in the discussion at the "Immobilienmanager-Unternehmerrunde".

You can read the complete article in german language here.

Source: Immobilienmanager Verlag IMV GmbH & Co. KG

20.11.2020: ESG as a corporate mission statement – Interview with Robert-Christian Gierth

Before the event “HEUER DIALOG Future Real Estate New Office - (R-)Evolution einer Assetklasse” on 24.11.2020 we had the opportunity to talk to Eva-Vanessa Ernst from Heuer Dialog GmbH about our corporate mission statement.


You can view the interview in german language here.

20.10.2020: Urban Real Estate Lab: Megatrend Homeoffice

A challenge for office, commercial and residential. Does supply and demand fit together? Alexander Happ talks about it.

You can view the video in german language here.

14.10.2020: Green becomes important

The climate debate has reached the real estate industry (...)

You can read the complete article in german language here.

Source: Süddeutsche Zeitung,

26.09.2020: Green Deal

For real estate companies, sustainability is a requirement for economic success - especially under the impact of the Corona pandemic.

You can read the complete article in german language here.

Source: raum und mehr - edition 2-2020,

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 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 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.


We look forward to hearing from you.

ASSIDUUS Development GmbH

Bleibtreustr. 34 10707 Berlin

+49 (0)30 403687400