Frank, you are a certified expert in hygrothermal building physics, noise control, and acoustics. You are also an energy advisor. Why and when did you pursue further training to become a Building Biology Consultant IBN?

In 2007, I was seriously ill with cancer. My wife and I then built a healthy, adhesive-free, mass timber house. A conventional building method would not have been an option. That’s why I pursued this path and completed the Building Biology Consultant IBN distance learning course in 2008. Combined with my experience building our house, the course was the catalyst for my career change. Previously, I worked at a management consulting firm, advising executives at large corporations. It wasn’t like that there. Now, I just want to do what I enjoy and what makes sense – providing real added value to my clients through building biology.

Did you establish your engineering firm GEWG to promote building energy efficiency and healthy living? What were your goals?

I started my company in 2013 after completing the part-time program in energy-efficient design at the University of Kassel. Initially, I was a one-person operation. I focused on residential and non-residential buildings, as well as historic structures.

1 My home is made of mass timber that does not use adhesives. The wall heating system is embedded in the interior clay plaster of the exterior walls.
2 The interior walls are also finished with thick clay plaster.
3 We incorporated slate stones from the surrounding area into one of our walls to create a connection between our home’s design and our natural environment.

Why did you decide to include building physics?

I believe in lifelong learning. Rather than resting on my laurels, I completed a certificate program in 2016 and became a certified expert in hygrothermal building physics. The subject has always interested me. In my work as an energy advisor, I have prepared many KfW Efficiency House certifications, always including detailed thermal bridge analyses and occasionally hygrothermal simulations. This experience prepared me for the course at the Energie- und Umweltzentrum am Deister e. V., as not many people in our region perform hygrothermal simulations using the WUFI® software from the Fraunhofer Institute for Building Physics (IBP).

In 2018, I completed a part-time certificate program in noise control and acoustics at the University of Weimar. By 2019, I had hired my first employees and founded a limited liability company (GmbH). I named this company GEWG Bauphysik GmbH. Our daily work focuses on building physics issues, always with building biology as a guiding principle.

4 After renovations guided by the principles of building biology, the facade of the former historic winery on the Mosel River shines once again.
5 The beautiful facade of the former oil mill was preserved, and mineral insulation was installed inside. WUFI® was used to calculate the interior insulation and ensure an energy-efficient design without thermal bridges. The interior of the historic building was renovated according to the principles of building biology.

You then became a certified Building Biology Energy Advisor IBN. How long have you been running a Building Biology Consulting Office IBN?

Since 2021. That was a good decision. Before that, I gave presentations at IBN continuing education seminars on „Building Biology + Energy“ and wrote articles for the Building Biology Magazine.

You are also a member of the International Association for Science and Technology of Building Maintenance and Monuments Preservation (WTA). In which area are you active?

I’m in the Building Physics Commission, specifically the Interior Insulation Working Group. Interior insulation is my passion. I’m also a member of FVID, the German association for interior insulation professionals. Other topics I cover include wood construction in renovation projects and moisture protection in wood construction. This brings us full circle. I approach renovating historic buildings differently than I do modernizing a town house from 1975. For historic buildings, I use materials that match the existing structure. There is a paradigm of material continuity. For example, if I have wood and clay, I renovate using those materials. If I have lime, I continue working with it, even for mineral interior insulation consisting of sand, lime, and air pores. It’s helpful to note that there are preservation guidelines. These guidelines ensure that even those unfamiliar with building biology use the appropriate materials.

Building biology criteria are easier to apply to historic buildings. How can these criteria be implemented in new construction?

Wood frame construction with cellulose or wood fiber insulation makes applying the principles of building biology easier than using sand-lime bricks, EPS, or rock wool. However, adhesives can be a critical issue in wood construction.

What do you enjoy about building biology design?

I enjoy that these clients approach building more consciously. They don’t just want something fast and cheap; they want something good, sustainable, ecological, and healthy. Working on a building biology project is naturally more enjoyable than working on a typical developer project.

You’re a sustainability auditor at the German Building Institute for Resource-Efficient and Sustainable Construction (BiRN). What sets you apart from an auditor for the German Sustainable Building Council (DGNB)?

BiRN is one of three accredited certification bodies for the QNG quality seal for sustainable buildings, which was developed by the German government. When we first brought in external DGNB auditors, we realized that the DGNB system is extremely comprehensive and time-consuming. This makes it expensive. Investors use the DGNB system for image management and marketing. However, they aren’t really interested in its substance.

The BiRN system is also complex, yet simpler and easier to implement. The costs for building owners are about half of those for the DGNB system.

I recommend BiRN because it benefits people. Certification costs range from 8,000 to 10,000 euros, with an additional 3,000 to 4,000 euros allocated for documentation, calculations, and consulting.

How much is the subsidy for a QNG seal?

It consists of an interest rate advantage of 20,000 euros compared to an average bank loan.

What was the smallest project for which you applied for a certification?

We currently have a series of tiny houses based on repurposed shipping containers in wood construction.

A steel shell is, of course, vapor-tight. Do you use renewable building materials to create a healthy indoor environment?

Yes, exactly. However, magnetic fields are not a criterion for certification.

Do you receive inquiries about new building materials, both approved and unapproved, such as straw or hemp lime?

I currently have a specific inquiry from an architect I regularly collaborate with regarding straw bale construction. That’s exciting, and I’m looking forward to it. If it works out, we can advise other clients on this alternative approach.

6 We provided support in terms of building biology and building physics for the renovation of a former industrialist’s mansion in the center of Luxembourg that was converted into a five-star hotel.
7 DThe mansion received capillary-active, vapor-permeable interior insulation, which was engineered to manage moisture based on WUFI® calculations, and the thermal bridges were optimized in 2D and 3D. The historic slate roof was retrofitted for energy efficiency from the inside.

What is your favorite project?

The renovation and conversion of a historic industrialist’s mansion from 1880 in downtown Luxembourg into a five-star hotel with 21 rooms. The building physics challenges were particularly exciting, such as retrofitting the historic slate roof, box windows, and interior insulation, as well as the underground passageway to the tunnel system beneath downtown Luxembourg.

Thank you for the interview!