Jonas, you are an energy consultant and a research assistant at the University of Applied Sciences in Bingen. Previously, you were a building services engineer specializing in heating, ventilation, and plumbing systems. When and why did you become a Building Biology Consultant IBN?

That was in 2023. We were looking for a new home ourselves. While researching indoor pollutants, I frequently came across the IBN website and looked at their continuing education offerings. Since I work in the construction industry, I found them very interesting and exciting. I can also apply that knowledge professionally. You should take advantage of synergies.

You received training to become an energy efficiency expert. How do energy-efficient construction and energy consulting factor into your work as a building biology professional?

I believe creating energy-efficient buildings is important. A building biology-based indoor climate has a lot to do with efficient construction. If my walls are warm, I am comfortable and do not need to heat as much. In energy-efficient buildings, it is especially important to pay attention to materials according to building biology criteria because today’s buildings are constructed to be very airtight. This makes off-gassing much more harmful.

1 Jonas Alef is checking the temperature control system for the concrete core. This system significantly reduces the required capacity of the chillers. At night, the system „charges“ the concrete core with cold air. During the day, the system supplies the cooling sails and ventilation systems.
2 An insulation kit containing natural insulation materials is available for on-site consultations. This allows clients to experience the insulation materials with all their senses.
3 Reed, cork, wood fiberboard, and cardboard are examples of ecological insulation materials recommended by building biology.

Do you recommend installing a ventilation system in a new home?

I prefer window ventilation. However, if you build a Passive House, you can eliminate the need for heating altogether. The ducts must be well-planned so they can be cleaned thoroughly and regularly. Otherwise, germs can build up inside them. If I were building a house for myself, I would choose traditional window ventilation and install outward-opening windows. You can leave these open for cross-ventilation because the wind will not slam them shut. I find sliding windows practical, even though they are not as airtight as other types of windows. Tilt-and-turn windows are also practical. Florian Nagler’s „simple“ buildings have tilt-and-turn windows, which are the subject of an interesting study.

From personal experience, I am not a big fan of decentralized ventilation fans. Even if they are quiet, you can still hear them because the fan changes direction every few minutes, briefly stopping and then starting again. Despite operating at under 30 dB, you can still hear the fan stop and start.

What are your thoughts on the current debate surrounding Germany’s Renewable Heating Act?

Whenever politicians propose new bans, there is always a lot of discussion. However, the transition must move forward. Whether or not the 65% rule is sensible, it is a step in the right direction. Fossil fuels must be phased out of the market. Although gas offers the cleanest combustion, not every home can be equipped with a heat pump. Installing them in densely populated areas would create an enormous amount of noise. It is not feasible. Similarly, not everyone can heat with wood. In urban areas, it would lead to high levels of particulate matter pollution.

There is no single system that works for everyone. My parents live on the edge of a forest and use storm-damaged wood to heat their masonry heater. For their building and location, that is the optimal heating technology. A good masonry heater burns wood relatively cleanly, and my parents have direct access to theirs. Wonderful!

Another resident without access to a forest installed an air source heat pump on a sunny, sheltered wall. In that case, it is a good solution.

More and more district heating networks are being established, especially in cities. This is the best option because nothing is burned locally. The heat is generated in a central location. New studies show that cold district heating networks and water-to-water heat pumps are highly efficient. These pumps draw the appropriate temperature from the cool network. The result is a large network with very low temperatures and minimal losses.

Are air source heat pumps sustainable?

Yes. Modern, well-designed heat pumps have an average annual coefficient of performance (COP) of 3.5, and this figure is increasing. This means that, on average, 3.5 units of heat are generated for every unit of electricity used over the course of a year.

Air source heat pumps already outperform some ground source heat pumps. Long-term evaluations of geothermal energy have shown that the actual heat flow in the ground is often lower than predicted. Consequently, average source temperatures of 0°C to 5°C (32°F to 41°F) may be reached in 20 to 30 years. In contrast, the nationwide average air temperature is 8.9°C (48°F) and rising. However, this technology is not suitable for all locations.

Are there any other innovations?

One new option that may interest urban areas is a brine heat pump combined with PVT modules because it operates silently. PVT modules are solar modules with a water-cooled heat transfer surface on the back. (Editor’s note: PV stands for photovoltaic and T stands for thermal energy.) The heat pump does not require a fan and can be located in the basement. When enclosed and decoupled from the building structure, it is generally inaudible. These modules are also cooled in the summer by heat dissipation. In winter, they remain snow-free because they can be defrosted automatically. This increases the annual electricity yield by approximately 10%. In 20 years, we will know how accurate the manufacturer’s claim is.

But what about the environmental impact of refrigerants?

While many refrigerants are harmful, refrigerant regulations are shifting the trend toward more environmentally friendly, natural refrigerants. In heating technology, this usually means propane. With a propane heat pump, there is no need to worry about storing it in the basement. These heat pumps typically have a gas sensor and a fan to prevent a flammable mixture from forming in the event of a leak.

During many basement inspections, I have seen camping gas cylinders with capacities three to four times larger than heat pumps, yet these cylinders lack any safety features.

You said that you find low-tech buildings more interesting than conventional ones. What constitutes an appropriate level of building automation for you?

To me, it means providing a sustainable and robust supply system while using as little technology as possible. For example, a heating system that controls the flow temperature based on the outside temperature is sensible and easy to implement because it does not need to run at full capacity constantly. The questions are: How much technology should I use? What benefits does it provide? What do I really need? It is good technology when you use a little and reap big rewards.

Do you think Florian Nagler’s approach to “building simply” is heading in the right direction?

Yes, I believe it is. The important thing to me is that the technology used is repairable or replaceable. Unlike with cell phones, you can replace the parts yourself. With good technology, all the parts are accessible.

Do you work for the Institute of Building Biology + Sustainability IBN as well?

I am an instructor for the in-person training sessions that accompany the online building biology course. I teach aspiring building biology consultants the fundamentals of building services engineering.

4 By measuring the concentrations of carbon dioxide and methane, we can determine whether green roofs permanently sequester or emit greenhouse gases.
5 On a semi-extensive green roof model, we will measure the effects on the microclimate, water balance, biodiversity, and greenhouse gas emissions and uptake.
6 Climate stations will measure climate parameters on the green roof and in a reference area around the clock.
7 For educational and informational purposes, we have a miniature green roof model in a glass case.
8 Our measurements at the University of Applied Sciences in Bingen demonstrate that mobile vertical gardens can mitigate heat islands in highly sealed urban centers and improve the microclimate.

What are your recommendations for staying cool in summer?

One low-tech option is to add greenery to roofs and exterior walls. Plants store and evaporate water, and they also provide shade. Trees are especially important for cooling buildings in summer. In winter, they lose their leaves, which allows sunlight to enter the building. In summer, they provide shade.

If you have a heat pump, you can use it to heat and cool your house. They are all reversible now. You just need a second small buffer tank. This setup works especially well with ceiling heating. It also works with wall heating.

In a central ventilation system, you can cool the supply air by spraying water into the exhaust air. This keeps the supply air hygienically clean and free of germs. The cardboard sprinkler element should be replaced about once a year. Night cooling is efficient and requires no additional technology – simply open all the windows on cool summer nights.

Which insulation materials provide the best protection against summer heat?

Materials with greater mass, such as wood fiberboard or blown-in wood fiber insulation, are more effective.

You are conducting research on urban greening at the university. How can urban greening be used to improve the urban climate?

At the University of Applied Sciences in Bingen, we focus on the sustainability aspect of the EMPOWER collaborative project and I work on the urban greening project. In this project, we study how semi-extensive roof and wall greening impacts the local climate, water balance, greenhouse gas emissions, and biodiversity compared to sealed urban surfaces.

Our cities need to be significantly greener. In my opinion, all flat roofs and facades in city centers that can support it should be required to be green. Ideally, these roofs would also be approved for „urban farming,“ such as cultivating food and ornamental plants. Raised beds could help provide part of the food supply.

Even simple green roofs can significantly improve the microclimate and increase the sedimentation of pollutants and fine dust.

Green spaces are important for insects to repopulate city centers. Birds follow the insects. Greening facades makes them look much better, too.

We installed photovoltaic modules on a green roof to test whether the electricity yield is measurably higher due to lower temperatures. We are also comparing different plant species and leaf mass. Some species grow better in partial shade. Green roofs and photovoltaics create a win-win situation.

Thank you very much for the interview!