Maxing Out Energy Self-Sufficiency: Houses That Fuel Themselves
Against the backdrop of skyrocketing electricity and gas prices, the idea of houses that produce their own energy is more attractive than ever.
WEIKERSHEIM — This corner of the state of Baden-Württemberg, in southwest Germany, is a popular tourist destination, boasting a Renaissance-era castle and the pretty old town center. But recently, Weikersheim has gained a new attraction for visitors interested in modern architecture and energy efficiency.
Walk down Bachgasse in the Schäftersheim quarter and you’ll find Hof 8, an award-winning development that has been praised not only for its modern conversion of the old farm buildings but also because the houses produce more energy than they use.
The renovated 19th-century farm has solar panels on every roof, innovative wind-energy installations, a groundwater pump and, of course, heavily insulated walls. An ingenious heating and energy storage system ensures the buildings are completely self-sufficient.
After standing empty for many years, the farm is now bustling with people once more: A midwifery practice has opened in the former stables, the old farmhouse is home to a planning office, and one building has been transformed into housing for the elderly.
Hof 8 offers the kind of lifestyle that many homeowners in Germany aspire to: being independent from fossil fuels and producing their own electricity and heating. The idea of energy self-sufficiency is especially attractive now given skyrocketing electricity and gas prices. Buildings have to meet certain requirements in order to be classed as energy-positive houses and qualify for financial support.
According to architect Rolf Klärle, it was never the aim to turn the farm into a mini power plant: “The idea was to optimize the farm’s energy use as far as possible. It turned out that we made it into an energy-positive house.”
Klärle didn’t come up with the idea of renovating the farm by himself. His sister Martina is the property developer. As children, they both lived opposite the farm. A few years ago, when the buildings were standing empty, Martina Klärle bought them and tasked her brother with renovating them. “The city originally wanted to tear down the buildings and build new homes,” says the architect.
The renovation cost around 2 million euros and took two years to complete. The project’s approach to energy goes far beyond what we normally see in a traditional house that has been spruced up to be more energy efficient: As well as producing electricity through wind and solar energy, the development has its own network of heat pumps, a ventilation system that recycles heat, charging points for electric vehicles, an LED lighting system and an innovative insulation system made from materials available onsite.
The advantages of owning an energy-positive house are shrinking.
Unlike other similar devices, the central heat pump doesn’t use air to store heat, but groundwater from the revitalized well, which significantly increases its yield, allowing it to heat 700 square meters of floor space throughout the development.
Even in winter, the electricity for the heat pump comes from solar panels. It needs 1 kilowatt-hour of solar energy to produce 5 kilowatt-hours of heat, giving it an annual performance factor of 5 — a figure that most heat pumps can only dream of.
Heat pumps have their limitations and generally work best at low flow temperatures. With that in mind, architect Klärle installed underfloor heating throughout the buildings that runs at 35 degrees.
But does the result justify the investment? The 2 million euros they pumped into the development will hardly be earned back through savings on electricity and heating costs. Rates for selling electricity back to the grid are also dropping, meaning the advantages of owning an energy-positive house are shrinking.
Solar panels are an interesting way of becoming self-sufficient as they last 25 years on average.
Recouping energy costs
Michael Bauer, a partner at consulting, planning and project management company Drees & Sommer, sees things a little differently: “These houses are worth the financial investment when the time it takes to recoup costs is less than the life expectancy of individual components,” he says.
Solar panels are currently worth the investment, as they recoup investment costs within around 10 years and have an average life expectancy of 25 years. Compensation for selling power back to the grid is becoming a less important factor, with the money saved on high energy prices playing more of a role.
There are still house builders who advise against the energy-positive house model. They say building a standard house that meets all current minimum energy regulations would cost 200,000 euros. Adding better insulation, solar panels and a ventilation system that recycles heat would increase costs by 25 to 30 per cent.
Bauer, from Drees & Sommer, disagrees. “This example is comparing apples with oranges,” he says. “The quality and comfort of the two buildings is not the same.” He claims the energy-positive house would be higher quality than the standard house and would therefore command a significantly higher sale price.
A mark-up of 25 per cent, plus the energy savings, would mean it would only take a few years to earn back the investment in green construction. Modern design and windows, underfloor heating, smart tech and many more features enhance quality of life and, according to Bauer, also increase the value of the property.
Bauer says that these benefits should be deducted from the money invested, which would reduce the additional costs cited by Town & Country Haus by half.
Houses doubling as power stations
Then there are also the government funds. The energy-efficient housing guidelines “40 plus” are supported by state-owned investment and development bank KfW. New builds can receive a loan of up to 150,000 euros and a subsidy of up to 37,500 euros. For existing buildings, the maximum loan amount is still 150,000 euros, but the subsidy can be up to 75,000 euros. Just half this sum, plus the increase in value as estimated by Michael Bauer, would cover a large proportion of the additional costs cited by Town & Country Haus.
In the future, we will have more electric cars and we will use green energy for heat instead of gas and oil.
Bauer suggests a pragmatic approach. “I advise every property developer to make their buildings as energy-efficient as possible and install as many solar panels as possible. If it turns out to be an energy-positive house, so much the better.” This was the case with Hof 8, which was not originally planned as a net energy producer.
Bauer believes that the ability to produce our own electricity will only become more important. “Technology is always developing. Heat pumps are becoming more efficient.” He is convinced that “in the future, we will have more electric cars and we will use green energy for heat instead of gas and oil.”
If homeowners are able to store the electricity they’ve produced for as long as possible and use it at a later date, that would mean more houses doubling as power stations — as in Weikersheim.
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