Timo Leukefeld is an expert for energy self-sufficient houses. He works i.a. as a consultant and honorary professor at the TU Bergakademie Freiberg.
The energetic refurbishment of the building stock is lagging behind. Why is that?
If I only renovate the heating or the building shell, I don’t change the costs for hot water, household electricity and the car. That’s why it hardly pays off, even with high energy prices and subsidies. As a landlord, I then have to add more to the cold rent than the tenant saves on warm rent. The usual user-investor dilemma.
(Image: Stefan Mays)
Do we need more funding?
Incentives are of little use, because the funding was actually very good in the past. In addition, Federal Economics Minister Robert Habeck has just reduced the funding for renewable energy technology, which is very annoying. My approach goes in the direction of the business model. We have to ensure that investors get reasonable amortization – and that tenants are not burdened.
What is your business model?
If the landlords energetically refurbish suitable multi-family houses with a south-facing roof all around and pack the roof and the facade full of photovoltaics, they are 50 to 70 percent energy self-sufficient – including hot water, household electricity and car. This means that, in addition to the building envelope, we are primarily concentrating on actively generating energy. And then you can offer an energy flat rate: the landlord guarantees the tenant a constant rent for five years, which includes heat, electricity and, in the future, even the charging of an e-car. This means that the landlord directs the money for the energy suppliers into his own pockets. In this way, he can earn three to four euros more per square meter without placing an additional burden on the tenants.
How the energy is calculated
Whether I charge for energy at a flat rate or based on consumption – isn’t that a zero-sum game?
No, because the entire utility bill is eliminated. It accounts for around 30 percent of the heating and electricity costs for tenants in new buildings. 30 percent! In addition, the landlord can generate the solar power for around eight cents per kilowatt hour and include it in this all-inclusive rent for 25 to 30 cents.
Has globalization come to an end for the time being? The new issue of the MIT Technology Review discusses how globalization can be shaped differently. The new issue is available from September 29th. in stores and from 28.9. easy to order in the heise shop. Highlights from the magazine:
Have you already implemented this model in practice?
Since 2018 we have planned a total of 385 residential units and partly built them with our construction partner. The tenants are totally enthusiastic because they have a fixed price over several years. Then you can also heat your living room to 22 degrees in winter.
Doesn’t this make the house an overly complex machine?
The other way around. We focus on radical de-technification. There is no heat pump, no underfloor heating, no bus control. There is only photovoltaic, battery and infrared heating – maintenance-free systems that last 30 years.
What is infrared heating made of?
These are panels on the ceiling, about two square meters for a twenty square meter room. They work with radiation, like a tiled stove, a campfire or the sun. This makes all surfaces warm – the walls, the floor, the table and so on. It costs half as much to install as a heat pump plus underfloor heating and nobody has to move out during the refurbishment.
However, the heaters have their highest power requirement in winter, when solar power is scarce.
With a new building or a renovation, we are close to the passive house, i.e. less than 20 kilowatt hours per square meter and year. The heating requirement in the existing building is up to 250 kilowatt hours. Some of our buildings use less electricity for heating than neighboring buildings that have not been renovated.
How large is the proportion of buildings that could be renovated using your model?
About 20 to 25 percent of apartment buildings. Among other things, they must have suitable roofs and must not be shaded. But even this 25 percent would be a huge leap compared to the one percent of buildings that are currently renovated each year.
“Anyone who has roof areas will have affordable energy in the future”
What about the rest of the houses?
Unfortunately there is little to help them. It takes decades to recoup the rehabilitation costs. As soon as they are dependent on external energy suppliers, they pay significantly more than if the buildings themselves produce energy. That’s why we’re noticing at the moment that the battle for the roofs has begun. If you have roof areas, you will have affordable energy in the future. If you don’t, you will have problems.
Would infrared heaters also help against a possible gas shortage in the short term?
Infrared is perhaps a little cheaper than traditional electric heating because it doesn’t heat the air. But heating with electricity is still much more expensive than with gas. And if you want to prepare for an emergency, you can assume that if the gas fails, the electricity will fail with a delay.
To home page