Our Team


Our people are the strength of IGG Building Economy. It is they who provide the unique input that give your project the financial foundation. The IGG advisers put the customer first and determine the right approach independently.

Because IGG works in a team, you always get the knowledge and experience of the entire company when hiring an expert.

Abdullah Altintas

Construction cost consultant

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Abdullah Altintas

Construction cost consultant


Abdullah graduated from Delft University of Technology with a specialisation in Design & Construction Management. During and after his studies he worked at a consultancy firm and a project developer.

Abdullah has been working at IGG since 2016 as a construction cost consultant and is involved in the preparation and testing of construction cost estimates, the execution of feasibility studies and consulting the client regarding construction costs for complex construction projects. The design and realisation process is complex, full of risks and requires good management with insight. As a cost consultant, Abdullah finds it particularly interesting to steer these complex projects in an early phase with creative and integrated solutions that lead to better results within the project frameworks of time, money and quality.

Abdullah is very involved, thinks proactively and looks for integrated solutions to realize complex projects. For IGG, Abdullah has, among other thins, been involved with the renovation and expansion of Paleis Het Loo in Apeldoorn, Hanzehogeschool in Groningen and the University of Groningen. He has also worked on various residential and non-residential projects.

Ahmed Ahmed

Construction cost consultant

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Ahmed Ahmed

Construction cost consultant


Ahmed completed his Master's in Building Technology at Delft University of Technology in 2018 in the field of load-bearing construction, building construction and building physics. For his graduation project, he focused on the development of a sustainable, innovative, transparent facade for non-residential construction. After his studies he worked at a consulting engineering firm.

Ahmed has been working at IGG since 2019 as a construction cost consultant, where his responsibilities are focused on drafting feasibility studies, estimates and budgets based on analysing complex construction projects during various design phases. Due to the increasing complexity of construction projects, adequate construction cost advice is fundamental to guarantee financial feasibility. As a result, Ahmed uses its building technology knowledge and expertise to provide clients with an integrated perspective on construction costs.

Ahmed is very driven to bring complex building projects to positive results, with potential risks being identified in time. This includes a proactive approach, a healthy relationship between quality and construction budget, customer focus and involvement in various residential and non-residential projects. These are also his driving forces.

Albert Simonis

Senior construction cost consultant / Projectmanager

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Albert Simonis

Senior construction cost consultant / Projectmanager


Albert studied Construction Technology at the Faculty of Architecture of the Technical University (previously Institute of Technology) Delft, where he graduated in 1973. After his military service, he worked briefly at an architectural firm. From 1977 he trained as a construction cost expert and worked at the Brink Group in Leidschendam.

Albert has been working at IGG since 1992 as a construction cost consultant, project manager, model builder and tutor. He deals with complex projects, and risk and feasibility analyses. He particularly focuses on projects that are in a very early development phase. He is also involved in procurement, legal issues, the development of the estimate models and the tutoring of young construction cost experts.

Albert has been involved in projects such as the restoration of Las Palmas in Rotterdam, the expansion of the mathematics faculty of the Eindhoven University of Technology in the monumental mechanical engineering hall, the redevelopment of the Caballero factory in The Hague and the new Stadskantoor Rotterdam.

Albert is very involved in the projects and provides a solid basis for the further development of the projects. He is also jointly responsible for the internal training process of the prospective cost experts within IGG.

Albert has been involved in projects such as the restoration of Las Palmas in Rotterdam, the expansion of the mathematics faculty of the Eindhoven University of Technology in the monumental mechanical engineering hall, the redevelopment of the Caballero factory in The Hague and the new Stadskantoor of Rotterdam.

Albert is very involved in the projects and provides a solid basis for the further development of the projects. He is also co-responsible for the internal training process of the upcoming cost experts within IGG.

Aleyna Karabulut

Construction cost consultant

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Aleyna Karabulut

Construction cost consultant


Aleyna completed her Architecture degree in 2013 at the University of Applied Sciences Rotterdam. After completing her education, she started working at a small architectural firm in The Hague. She worked here for a year as an architectural drafter.

It soon became apparent that she wanted more control over construction costs and that is why she started as a junior calculator at a medium-sized construction company in Wateringen. She worked on various housing projects for three and a half years. In order to learn more about construction costs, she followed the course Construction costs at the HTI (Higher Technical Institute) in Amsterdam during her career with this contractor.

Aleyna has been working at IGG since 2019 as a construction cost consultant. She is involved in various residential and non-residential projects.

Arno Vonk MRICS

Director / Senior construction cost consultant

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Arno Vonk MRICS

Director / Senior construction cost consultant


Arno studied Architecture and his Masters in Management in The Built Environment at Delft University of Technology, where he graduated with honourable mention in 2003. Arno joined IGG in 2004 as a plan economist and since 2012 he has been the director / owner of IGG. He is involved in complex non-residential projects and area developments. The strength of his work lies both in the early phase of a development, in order to steer the project in the right financial direction, and in the later phase, when design optimisations are required within the desired quality and financial frameworks.

Arno has been involved in projects such as the expansion of the Amsterdam ArenA, Differ Eindhoven and Twenty4Amsterdam. He is also the founder of the BouwkostenKompas with the uitgaven Woning- en Utiliteitsbouw, GWW en Installaties.

Arno is very involved in the projects and always ensures that projects are realized within the set budgets while maintaining the aesthetic core qualities.

Ashley Ramsey

Construction cost consultant

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Ashley Ramsey

Construction cost consultant


Ashley is studying Construction Management & Engineering at the Faculty of Civil Engineering of Delft University of Technology. In 2015, during her final year of her Bachelor's degree in Architecture in Delft, she joined IGG to research the costs for building permits in Dutch municipalities. Since then she has been working, alongside her studies, as a construction cost consultant at IGG.

Ashley participates in various residential, non-residential and renovation projects within IGG, where she supports the team on various parts of the projects.

Awinash Baldew

Construction cost consultant

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Awinash Baldew

Construction cost consultant


Awinash started his study Architecture at the MTS in 2008 and continued this at the HTS in Rotterdam. During his HTS education, he worked part-time at a multidisciplinary engineering firm. Doing this, he came into contact with construction costs and maintenance & operation; he has not let go of this since. In order to learn more about construction costs, he attended the construction costs training course at the HTI (Higher Technical Institute) in Amsterdam after completing the HTS.

Since 2017, Awinash has been working as a construction cost consultant at IGG. In addition to his responsibilities such as making cost estimates, construction cost advice, scenario studies, second opinions, construction cost management, investment calculations and operation budgets, he is involved in a wide variety of complex projects.

Awinash advises on construction costs in all phases of a construction cycle. Together with the people involved, he always tries to find a way, otherwise he makes one. Bart has followed his study Architecture at Delft University of Technology and has specialised in the redevelopment of industrial heritage for his master's degree in Architecture. Since 2017, Bart has been working at IGG as a construction cost consultant, where he has gained experience in both large-scale residential and non-residential construction and airports in both the preparation and execution phases. He is also involved in sustainable building and LCC within IGG. Bart has therefore obtained his certificate as a BREEAM expert at IGG.

Bart Kuipéri

Construction cost consultant

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Bart Kuipéri

Construction cost consultant


Bart has followed his study Architecture at Delft University of Technology and has specialised in the redevelopment of industrial heritage for his Master's degree in Architecture. Since 2017, Bart has been working at IGG as a construction economic consultant, where he has gained experience in both large-scale residential and non-residential construction and airports in both the preparation and implementation phases. He is also involved in sustainable building and LCC within IGG. Bart has therefore obtained his diploma as a BREEAM expert at IGG.

For IGG, Bart was involved as a construction cost consultant in, among other things, the Air Traffic Control Tower projects at Kuwait International Airport and project Toren van Oud in The Hague. He also worked on behalf of IGG at Schiphol Airport for six months for the Cost Expertise Center at Schiphol Group and is currently involved in the construction of the new A-Terminal at Schiphol from the Capital Program.

Bart's strength is his creativity, quality / relationship-oriented approach and hands-on personality. His qualities lie in operating at the common ground between technology and business, where his skills in the field of concept development and knowledge of the construction sector can be fully appreciated.

Bart-Jan Schets

Construction cost consultant

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Bart-Jan Schets

Construction cost consultant


Bart-Jan completed his Bachelor's degree in Building Engineering Business Administration in 2015 at the Avans University of Applied Sciences Tilburg. His joint graduation research focused on creating an improved tender process at Hurks Bouw's s-Hertogenbosch, where the search for the correct answer to the increasingly complex customer demand was central.

After his studies, he started his career at various employers both within and outside the construction sector to create as many insights as possible. These insights have led to a clear vision in which Bart-Jan wants to develop in the area of construction consultancy, where his interests and qualities can be fully appreciated. Since 2019, Bart-Jan has been working at IGG as a construction cost consultant.

In addition, Bart-Jan is driven by topics such as efficient, sustainable, circular, demountable, smart & data-driven building and working.

Bas van der Zanden

Construction cost consultant

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Bas van der Zanden

Construction cost consultant


Bas has completed his Bachelor in Build and Environment at the Faculty of Architecture of the University of Applied Sciences Utrecht where he specialises in Construction Management. In addition to his Bachelor's degree, he has obtained the Installation Technology certificate at the Avans faculty. After completing his studies, he gained a year-long work experience at Techniplan as a mechanical technician.

Bas has been working at IGG since 2016 as a construction cost consultant. He has since been involved in various projects, such as the Tijdelijke Huisvesting Tweede Kamer in The Hague, the Haut residential tower in Amsterdam, the transformation of Westerpark West (parts of Zout, Peper and Kavel 3), various apartment buildings including De Sniep in Diemen, Waterfront in Amsterdam, City Icoon in Amsterdam, Zalmhaven in Rotterdam and Kruisvaartkade in Utrecht. Bas was also involved in the execution of work for various airports such as Imam Khomeini in Iran, Gateway 2030 in Aruba and the Capital Programme of Schiphol Real Estate. In the latter project Bas worked mainly on the development of the new A-Terminal.

In addition to the above projects, Bas is also involved in the preparation of NEN reports and the performance of building permit cost verification.

Ben van der Hoeven

Construction cost consultant / Projectmanager

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Ben van der Hoeven

Construction cost consultant / Projectmanager


Ben has followed his study Architecture at the University of Applied Sciences Rotterdam. After that he completed his Master's degree in Real Estate Management and Development at the Eindhoven University of Technology in 2013 and in the meantime gained around 8 years of work experience with various developing contractors. Since 2017, Ben has been working at IGG as a construction cost consultant.

The practical experience and theoretical knowledge of Ben in both technical and economic terms form the basis for giving clients good advice. With this, he can be deployed in all areas that affect the construction costs. For IGG, Ben has been involved in various projects such as Tijdelijke Huisvesting Tweede Kamer in The Hague, construction cost management for all COA locations, the updating of land and real estate exploitation for the Municipality of Binnenmaas, building permit cost verification and Transformatie EuroPlaza in Amsterdam.

Chiara van der Veen

Tender and conctractmanagement

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Chiara van der Veen

Tender and conctractmanagement


Chiara has a Bachelor's degree in Real Estate Management from the University of Applied Sciences Rotterdam and subsequently studied Real Estate Studies at the University of Groningen. During her studies she has always been interested in innovative and leading construction projects.

Chiara has been working as a contracting and tender consultant since 2019 and is involved in various projects.

Cor Guyt

MEP consultant

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Cor Guyt

MEP consultant


Cor has gained a lot of theoretical knowledge of MEP through attending technical education (LTS, MTS and HTS). The practical knowledge has been gained by working at several MEP companies and consulting firms.

His knowledge and experience of both the design and implementation of MEP ensure that he is a good sparring partner and that he can prepare complete, realistic and competitive cost estimates.

Djordy van Laar

Construction cost consultant / Projectmanager

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Djordy van Laar

Construction cost consultant / Projectmanager


Djordy completed his Master Building Engineering at TU Delft in 2015. During his graduation project he focused on optimising demountable and modular stadiums. Sustainable building concepts that are increasingly gaining popularity today.

After a brief period at Octatube in Delft, Djordy joined IGG in 2016. Here he contributed as a construction cost consultant to various residential non-residential projects such as Oosterdokseiland Kavel 5b-6, also known as the headquarters of Booking.com; HAUT, the - for the time being - highest wooden residential tower in the Netherlands; the renovation of the Goede Doelen Loterij on the Zuidas; and, to a feasible extend, the circular development of The Dutch Mountains.

Djordy is driven by innovation both during his studies and in his professional career. Within his projects he tries to push existing boundaries and in this way gain maximum value for the customers he serves. That maximum value is often an interplay between (life cycle) costs versus revenues, sustainability and social value. The qualities of Djordy are best reflected in the strategic design phase, when the business case of projects is addressed and in which he can translate abstract concepts such as innovative, sustainable, circular, energy neutral, healthy concrete value and costs for its clients.

Since his participation in the Big Data lecture series (Nyenrode), Djordy has been involved in the development of IGG in the field of (big) data and automation. By drawing up a strategy; targeted partnerships; pilots and tools, he contributes to the change from IGG to an as much data-driven organisation as possible.

Dounya Anthonio

Office management

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Dounya Anthonio

Office management


Dounya has been working alongside her studies at IGG since 2018. She is responsible for the administration of Calcsoft BV, also known as the BouwkostenKompas. In addition to these activities, she organises project visits, company events and is involved with updating the website and social media platforms.

Erik Terlouw

Senior construction cost consultant / Projectcoach

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Erik Terlouw

Senior construction cost consultant / Projectcoach


Erik started his study Architecture at the MTS and continued this at the HTS in Rotterdam. At his first employer, he came into contact with the construction costs component and this has not let him go since. After following the study Calculator U-Bouw at the HTI (Higher Technical Institute) in Amsterdam and his, now more than 20 years of experience, he has become a cost expert with a broad knowledge in the most diverse and special projects in non-residential building.

From 1996 to 2017, he worked in various positions at several large contractors, but construction costs has always been a central theme, making his knowledge so broad that he can handle any problem.

Erik has been working as a senior cost expert at IGG since 2017. In addition to his responsibilities such as drawing up estimates and budgets, reviewing plans and budgets and advising the client on construction costs, he is also a source of information for his colleagues through his experience. Erik's strength is his professional and analytical approach to the fulfilment of tasks and objectives, his communication skills and his persuasiveness and decisiveness. In addition, the ability to bridge the gap between abstract construction costs and executive construction is a specialty based on his experience.

Esther Malherbe

Office management

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Esther Malherbe

Office management


Esther has been working at IGG since 2018. She is responsible for project administration, facility management and organises the volleyball tournament every year.

Gerard van der Heiden

MEP consultant / Projectmanager

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Gerard van der Heiden

MEP consultant / Projectmanager


Gerard started his working life at a MEP company where he was involved in designing, calculating and drawing building-related MEP. He now has considerable experience in various functions within the MEP technology. These positions varied from technical advisor to project manager.

In recent years he has gained experience as a cost consultant at a MEP company.

Gerard has been working at IGG since 2019 as MEP cost consultant. He focuses primarily on drawing up estimates and budgets for the MEP design. He is also a source of information for colleagues with regard to sustainability ambitions and MEP issues.

Gerard's strength lies in his analytical approach to projects and his process-based way of working.

Gert-Jan Houtepen

Construction cost consultant / Projectmanager

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Gert-Jan Houtepen

Construction cost consultant / Projectmanager


Gert-Jan has completed his Master's degree in Real Estate Management & Development at the Faculty of Architecture of Eindhoven University of Technology and graduated in 2016 on the theme Conceptual Building. In addition to his Master's degree, he has obtained the Technical Management certificate at the faculty of Technical Business Administration. During his studies, Gert-Jan worked for several years as a drafter at Olivier + Partners Architects, which specialises in healthcare. Gert-Jan has been working at IGG since 2016 as a construction cost consultant and is also involved in procurement consultancy, among other things.

For IGG, Gert-Jan has been involved as a construction cost consultant in the projects Oosterdokseiland Kavel 5 and 6 in Amsterdam and Havenkwartier in Rotterdam. As a procurement expert, this included the headquarters of NS (Laan van Puntenburg) in Utrecht.

Gert-Jan's strength is his involvement, both with the project and with the client, his eagerness to learn and his analytical skills.

Gilbert Coers

Account manager

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Gilbert Coers

Account manager


Gilbert always seeks for the best possible situation, combination or relationship. With his background in (HTS) technology on the one hand and communication & philosophy on the other, he brings people together. With the aim that all parties win, with each other.

How inspiring is it, with the best specialists on board and always within the set budget, to realise appealing projects and to brighten up our communal environment?

Together you know more, you are stronger and you perform better.

Guido van Veen

Construction cost consultant

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Guido van Veen

Construction cost consultant


In 2014, Guido completed the Master's degree in Construction Management & Engineering with honourable mention at the Faculty of Architecture at Eindhoven University of Technology. Before his Master's degree, he obtained his Bachelor's degree in Building Management at the University of Applied Sciences Amsterdam. After his study period, he worked for one and a half years as an asset manager at Arcadis and has been working at IGG since 2016 as a construction cost consultant.

Guido has been working full-time as a cost manager for the large-scale and multidisciplinary Schiphol A-area project. He now focuses on various residential and non-residential construction projects, as well as renovation and healthcare projects.

The strength of Guido is his customer focus, inquisitiveness and involvement in projects. Hans studied Architecture at the MTS in Leiden and then at The Hague University of Applied Sciences (HTS). After this, he worked as a project manager at various construction companies. After completing his post-HBO Construction Cost Expert and BOB trainings, he started as a construction cost consultant.

Hans Smit RKN

Register costmanager (RKN) / Projectcoach

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Hans Smit RKN

Register costmanager (RKN) / Projectcoach


Hans has been working at IGG since 2012 as a construction costs consultant and is involved in complex construction projects where he is a proactive, result-oriented cost manager. Hans comes across as a professional and has broadened his knowledge in areas such as operating costs, renovation projects and museums. Based on his experience, knowledge and quality, Hans was recognized as a Register Kostendeskundige in 2017.

Irene Bointon

Office management

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Irene Bointon

Office management


Irene has been working at IGG since 2010. She is responsible for accounting, financial and personnel administration.

Jan Schellekens

Register costmanager (RKN)

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Jan Schellekens

Register costmanager (RKN)


Jan is called the old-timer specialist in USA-type of MasterFormat specification writing for Architectural and Structural Works. He uses intelligent master guide specification writing software with continuously updated data-bases, updated through the world’s current building industry.

Jeroen Hilbrands

Construction cost consultant / Projectmanager

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Jeroen Hilbrands

Construction cost consultant / Projectmanager


Jeroen graduated in Architecture and Construction Engineering at the Hague University of Applied Sciences.

During his education, he gained practical experience at a municipality, architecture firm and various contractors. From that time on, he prefers to give architectural financial advice and has gained some knowledge and experience with a cost consultancy.

Since 2018, Jeroen has been working at IGG as a construction cost consultant. He is involved in, among other things, drawing up estimates and budgets for several projects in various construction phases. Testing budgets and fees, advising project teams and clients on construction costs are also among his specialties.

John Koks

Senior construction cost consultant / Projectcoach

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John Koks

Senior construction cost consultant / Projectcoach


John started his engineering studies at the MTS and continued this at the HTS in The Hague. During the early days of his career, John worked as a CAD drafter and project manager at various architectural firms, continuing his studies at the HES in Rotterdam, where he studied Post H.T.O. Business Administration and John successfully completed the Real Estate Management training.

From 1999 to 2017, John worked at Atelier PRO as a construction cost expert and project manager. During his career at PRO he followed the courses Building cost expert, Budgeting in the Design phase, tendering specification surveyor STABU, ""Calculating on Real Estate"" and ""Entrepreneurship in Construction"" (TU-Twente). In addition to construction cost consultancy, his responsibilities consisted of office coordination, including (project) budget monitoring, manpower planning and quality assurance. Starting in 2006, John develops and coordinates the use of BIM with regard to costs and specifications within design and execution processes. Part of this is also sharing knowledge in this area with project partners and clients, such as the Luxembourg government. In 2017, John joined IGG as a senior construction cost consultant and BIM specialist. His responsibilities are: preparing estimates and budgets, reviewing plans and budgets, consulting the client on construction costs, advising the project teams and clients on the regulations, as well as supervising and managing projects in design and execution. For IGG, John is involved in the Schiphol A-area, the Lego Discovery Center in Scheveningen and the reallocation of the Ambachtsschool in Enschede.

In addition to his work at IGG, John is also a guest lecturer at the post-graduate course Building cost expert.

Leon Turenhout

Construction cost consultant

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Leon Turenhout

Construction cost consultant


Leon has followed the Bachelor studies Spatial Development at the INholland University of Applied Sciences, where he specialised in Construction Management and Real Estate. Before Leon started his study Spatial Development, he completed his Architecture degree (MBO level 4).

During his studies, Leon gained experience abroad has worked at various contractors, the municipality and a project developer. Here Leon came into contact with construction costs several times. This has also motivated him to further develop himself as a construction cost consultant.

Since joining IGG in 2018 as a construction cost consultant, Leon has been involved in the large-scale and multidisciplinary Schiphol A-area project.

Luca Pieck

Construction cost consultant

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Luca Pieck

Construction cost consultant


Luca completed his Bachelor degree in Architecture at TU Delft in 2019. During his studies he developed a passion for large-scale construction projects. He has started at IGG in 2019. IGG is his first employer and gives him the opportunity to contribute as a construction cost consultant to such a project: the development of the Schiphol A-area project. Here he has a supporting role in the Programme Management Office-team. Their main task is to professionalise, standardise and economise the various projects in the program.

Lynsey Merling Meijer

Office management

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Lynsey Merling Meijer

Office management


Lynsey joined IGG in 2020, she is a management assistant and responsible for marketing activities.

Marc Hengstmangers

Director / Senior construction cost consultant

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Marc Hengstmangers

Director / Senior construction cost consultant


Marcel started his Architecture degree at the MTS-Arnhem, oriented on execution. After the MTS training, he gained work experiences as a carpenter in a carpentry factory and then at a construction company. Marcel was then given the opportunity to further develop himself by following the BOB training, estimator and work organizer for the construction company. After these courses, he started an internship at Brink Group, where he was later hired and further developed his calculator skills in the area of budgets based on the STABU system and the object oriented budgets according to the NL SfB 'Elementenmethode'. At the Brink Group, Marcel attended the Building Cost Expert training at the Hague University of Applied Sciences.

From 2000 to 2019, he worked in various positions at both engineering firms and construction companies, but always followed the construction costs as a common thread, making his building knowledge so broad that he can handle any problem. From 2004 to 2010, Marcel worked as a construction cost consultant and project manager at ABT. At ABT, Marcel has also followed the training for project manager (POA) as a specification surveyor STABU. At G & S Bouw, Marcel has gained a lot of experience with budgeting based on 3D BIM models.

Marcel has been working as a cost consultant - project manager at IGG since 2019. In addition to his duties such as drafting estimates and budgets, reviewing plans and budgets and advising the client on construction costs, he is also a source of information for his colleagues through his experience. Marcel's strength is his professional and analytical approach to the fulfilment of tasks and objectives, his communication skills and his persuasiveness and decisiveness. In addition, the ability to build bridges between abstract construction costs and executive construction is a specialty based on his experience.

For IGG, Marcel is involved in the large-scale and multidisciplinary Schiphol A-area project.

Marcel Dhaenens

Senior construction cost consultant / Projectmanager

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Marcel Dhaenens

Senior construction cost consultant / Projectmanager


Marcel started his Architecture degree at the MTS-Arnhem, oriented on execution. After the MTS training, he gained work experiences as a carpenter in a carpentry factory and then at a construction company. Marcel was then given the opportunity to further develop himself by following the BOB training, estimator and work organizer for the construction company. After these courses, he started an internship at Brink Group, where he was later hired and further developed his calculator skills in the area of budgets based on the STABU system and the object oriented budgets according to the NL SfB 'Elementenmethode'. At the Brink Group, Marcel attended the Building Cost Expert training at the Hague University of Applied Sciences.

From 2000 to 2019, he worked in various positions at both engineering firms and construction companies, but always followed the construction costs as a common thread, making his building knowledge so broad that he can handle any problem. From 2004 to 2010, Marcel worked as a construction cost consultant and project manager at ABT. At ABT, Marcel has also followed the training for project manager (POA) as a specification surveyor STABU. At G & S Bouw, Marcel has gained a lot of experience with budgeting based on 3D BIM models.

Marcel has been working as a cost consultant - project manager at IGG since 2019. In addition to his duties such as drafting estimates and budgets, reviewing plans and budgets and advising the client on construction costs, he is also a source of information for his colleagues through his experience. Marcel's strength is his professional and analytical approach to the fulfilment of tasks and objectives, his communication skills and his persuasiveness and decisiveness. In addition, the ability to build bridges between abstract construction costs and executive construction is a specialty based on his experience.

For IGG, Marcel is involved in the large-scale and multidisciplinary Schiphol A-area project.

Marian de Groot

Office management

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Marian de Groot

Office management


Marian has been working at IGG since 2004 and is responsible for project invoicing and administration.

Mario Van Veen

Construction cost consultant / Projectmanager

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Mario Van Veen

Construction cost consultant / Projectmanager


Mario started his study Architecture at the MTS and gained his practical experience at various architectural firms and contractors. He then studied the Construction Cost Management at the HTS.

Mario has been working at IGG since 2014 as a construction cost consultant and is involved in, among other things, preparing estimates and budgets, reviewing budgets, advising the client on construction costs and developing the knowledge level of the current construction market. In the role of cost consultant, he is very involved and gives advice at an early stage on the design and the development process to guide them towards a good cost and quality ratio, so that as many financial risks as possible can be made transparent or be excluded.

Meloek Mlihi

Construction cost consultant

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Meloek Mlihi

Construction cost consultant


Meloek graduated with honourable mention at TU Delft in 2018, during her studies she gained experience as a student assistant at TU Delft, CBRE and Octatube. During the period of her Masters in Management in The Built Environment, she also completed a semester at the ETH in Zurich.

Since 2019, Meloek has been working at IGG as a construction cost consultant. With her creative spirit, she brings fresh perspective to the company. She is straightforward and does not mince words, which means she can speed up her work when needed. She is very involved and can exert this power in the workplace with her ""Yes-we-can"" attitude.

Meloek is currently involved in the development of the Schiphol A-area project, including the new A-Terminal. Other projects that Meloek worked on are residential buildings: BABEL on the Lloyd Pier in Rotterdam and the Rivergarden in Capelle aan den IJssel, a mixed building VIEW in the centre of Rotterdam, tree residential buildings Westerpark-West in Amsterdam and Zomerhofkwartier, a small and dense redevelopment of urban areas in Rotterdam.

Radjen Doekharan

MEP consultant

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Radjen Doekharan

MEP consultant


After his studies at the LTS, Radjen immediately started working at a medium-sized MEP company in Zwijndrecht. He has also followed various studies, such as the TSI high-voltage power plant technician, in the evenings. During his career, he worked as a (main) calculator at various MEP companies. Radjen also gained a lot of experience at a large MEP consultancy as a cost consultant.

Since 2018, Radjen has been working as a senior MEP cost consultant at IGG. In addition to his responsibilities such as making cost estimates, providing MEP cost advice, drafting second opinions, investment calculations and operating budgets, he is involved in a wide variety of complex projects.

Radjen provides advice on building-related MEP costs in all phases of a construction cycle.

Rien Prins

Senior construction cost consultant

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Rien Prins

Senior construction cost consultant


Rien is driven, creative and decisive, he is open to new developments and likes to share his experiences with others.

He gained his years of experience in the field of cost management, project planning and project management at various employers, before he founded his own company in 2013. The first years of his career he worked for a major client. In the last 10 years he has done many international projects for that company. After 1999, he worked at (small and large) consultancy firms and his specialisation in costs was further developed.

In addition to the projects that he has been carrying out since 2013 as an independent entrepreneur, he is affiliated with a large internationally oriented engineering firm for which he issues cost advice and performs cost management tasks for both small and large projects, for new construction, renovations or maintenance.

Rob Passchier (RKN)

Register costmanager (RKN) / Projectcoach

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Rob Passchier (RKN)

Register costmanager (RKN) / Projectcoach


Rob studied architecture at the HTS in The Hague and from that moment on has been interested in the possibilities of computerisation and digitisation. He uses his analytical ability to apply calculation models to problems. If there are none or unclear frameworks for an issue, he will start there. He does not hesitate to point out unrealistic budgets to the client and he identifies risks at an early stage, so that there is sufficient time to anticipate them. Identifying bottlenecks and coming up with solutions are inextricably linked.

He has a background of more than 15 years as a construction cost consultant at a medium-sized architectural firm and a construction cost consultancy, and has gained a lot of experience with school construction, care institutions and large housing projects. Rob has been working at IGG since 2013. He is particularly interested in lifecycle costs, as these can be strongly influenced during the initiation and design phase. After all, the essential choices are made here in terms of MEP, materials, components, etc.

Sustainability is therefore logically an extension of the areas of interest, because sustainable use of materials can help to limit the lifecycle costs.

Sietse Hoekstra

Construction cost consultant / Projectmanager

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Sietse Hoekstra

Construction cost consultant / Projectmanager


Sietse started his architectural career at LTS Architecture at the former Willem Blaeu in Alkmaar. After completing LTS Architecture, Sietse continued his school career at Horizon College in Alkmaar. There he successfully completed primary and secondary carpentry training.

After a short trip to the construction site (1999), Sietse discovered that his interest is in calculating, preparing and supervising construction projects. After completing the Calculator / Work Planner course at Horizon College in Alkmaar, he came into contact with the budgeting and calculation of construction projects in civil and utility construction. To broaden his knowledge in the field of architecture and business economics, he followed a B&U calculation course at BOB training and Small Business and Retail Management at INholland in Haarlem.

From 1999 to 2012 and from 2016 to 2019, Sietse worked as a calculator / planner, project manager and manager at various medium-sized contractors in North-Holland. From 2012 to 2016 he owned his own building management agency. The company focused on independent calculation, preparation and start-up of various projects both in the Netherlands and abroad.

Since 2019, Sietse has been working as a project manager and construction cost consultant at IGG. In addition to drawing up estimates and budgets, and testing budgets, he can consult on construction costs form initiation to execution phase using his practical architectural experience. In this way he can also contribute to making complex construction and technical issues practical.

Steven Oosterling

Senior tender and contractmanagement / Projectmanager

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Steven Oosterling

Senior tender and contractmanagement / Projectmanager


Steven is an all-round project leader who has supervised construction and real estate related projects for both clients and contractors. In recent years he has specialised in tenders, where he has sat on both sides of the table.

In the role of tender manager or consultant, he has since been involved in more than 80 tenders. His Architectural (HTS) and Public Administration (University) background comes in handy here.

For Steven, a tender is never a goal in itself, but always a means to make projects a success. After all, basically a tender is nothing more than asking the market a question and ensuring that a good answer is given. Preferably several, because then there is something to choose from. By not only organising the tendering procedure, but also formulating the request correctly, the chance of a correct answer considerably increases. A tender forms the basis for future cooperation.

Steven has been working at IGG since 2016 and is always closely involved in his projects, where the interests of the client always come first.

Sui Ming Li

Senior construction cost consultant / Projectmanager

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Sui Ming Li

Senior construction cost consultant / Projectmanager


After the HTS in Rotterdam, Sui Ming started at Randstad Polytechniek (technical employment agency) as a structural draftsman or employee. He has worked here on various residential and non-residential construction projects, for architects and engineering firms, municipalities and construction companies.

From 1996 to 1998, he worked for Arcadis Bouwinfra as the first architectural draftsman for the development of De Resident project between Central Station and The Hague Municipality. Sui Ming had previously indicated that he wanted to gain cost knowledge from the cost department, but unfortunately that was not possible at the time.

In October 1998 he started as a calculator at Ingenieursbureau Multical. There he drew up the cost estimates for various types of construction projects. He supports the Specifications Department with surveying specifications. After obtaining his diploma of the basic training Construction Cost Expert at the Hague University of Applied Sciences in 2005, he started growing as a construction cost consultant, where he can run projects independently.

From 2006 to 2019, Sui Ming works at Aronsohn advising engineers as a construction cost consultant and since 2015 also as a specification surveyor after following the training Specification Surveyor for residential and non-residential construction. Within Aronsohn Constructies, he prepared the structural cost estimates from schematic design up to and including the tender phase for all large and complex projects, such as the new construction of the Erasmus MC in Rotterdam, Meander MC in Amersfoort, Renovatie Sportpaleis Ahoy and Stadskantoor Deventer. He has also written the structural specifications for projects such as Oosterdokseiland kavel 5b / 6, renovation Naturalis and OCC Spuikwartier.

For the Aronsohn Management department, he made structural budget estimates for many universities such as UvA, VU, RUL, TUD, TU/e and RUU and he assessed contract variations for all current projects. Aronsohn has been working with BIM since 2010, so all projects are modeled with Revit and as a result he gained a lot of knowledge about working with BIM and drawing up cost estimates based on the IFC model.

Sui Ming joined IGG in 2019 as a senior construction cost consultant. His duties consist mainly of drafting budgets, checking plans against budgeting and consulting clients on controlling construction costs.

Ton de Groot

Certified Construction Cost Expert

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Ton de Groot

Certified Construction Cost Expert


Ton has a true eye for talent and once hired Arno Vonk and Marc Hengstmangers. From 2012 there was a co-partnership between Ton and Arno and since 2017 he has left his company with piece of mind in the capable hands of Arno and Marc. Ton, however, has not yet disappeared from the company; he symbolises the bridge between the previous generation and the new talents, and cherishes his ties with the clients.

Yuk-Ling Chung

Construction cost consultant

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Yuk-Ling Chung

Construction cost consultant


Yuk-Ling studied Architecture and Construction Engineering at the Hague University Of Applied Sciences and specialised in constructions during her studies. She has always been interested in calculations and figures during the course of her studies. Since 2018, Yuk-Ling has been working as a construction cost consultant and she is involved in various residential, non-residential, civil engineering and renovation projects.

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