Nearly one third of Germany’s primary energy production goes into heating private households. The average older apartment building consumes more than 20 liters of heating oil per square meter
every year. And this has consequences, both for the tenants because they have to pay ever higher heating bills, and for the environment, because heating produces considerable amounts of the
greenhouse gas carbon dioxide (CO2). But something completely different is going on at the zero-heating cost house in the Pfingstweide district of Ludwigshafen. The apartments there don’t even
have conventional radiators, not to mention stoves. Instead, a sophisticated compound system with innovative insulation and ventilation ensures that the residents always enjoy comfortable
temperatures and that hardly any CO2 is released. Both the design and the modernization work were done by BASF’s housing company Luwoge and its subsidiary Luwoge consult, a consulting firm for
energy-efficient construction.

For several years now, Luwoge has been showing that BASF products and other components can be used to construct or modernize buildings and apartments to save energy. In 2001, for example, the
company modernized a 1950s-era building into a low-energy house – making it the first building from that period to be transformed into a 3-liter house. Since then, the annual heating oil
requirements for this building have remained below three liters per square meter of living space. According to Karl Arenz, the director of Luwoge’s Competence Center for Housing Construction
and Modernization, “We have lots of expertise in transforming old buildings into modern low-energy houses. Our 3-liter house was just a pilot project. Back then we wanted to show what was
technically feasible – the profitability aspect was secondary. Now with the zero-heating cost house, we’re demonstrating that energy-efficient modernization of buildings also makes a lot of
business sense.”

In order to actually eliminate heating costs, a multi-stage compound system is used. First of all, the building is well lined with thermal insulation panels made of Neopor©. In the
insulation sector, the newcomer Neopor© has far outpaced its ancestor Styropor©. It contains tiny graphite particles that reflect thermal radiation and give the material a silver-grey
hue. The windows in the zero-heating cost house also provide the best possible protection against energy dissipation – they are triple-glazed and contain an inert gas filling between the panes.

Another component in this building’s energy-efficient strategy is its actual heating system. There isn’t a single radiator in the entire building – although the “zero-heating cost” house is not
a “zero-energy consumption” structure. Although this may look like a paradox, it simply means that the building earns its own (low) heating costs. To do so, it uses solar energy. Solar cells on
the roof generate electricity, which is fed into the municipal grid. Revenues from this contribution cover the costs for keeping the apartments warm. The zero-heating cost house also takes care
of its own hot water needs – with solar panels on its southern side. As Karl Arenz explains, “A controlled incoming and outgoing ventilation system with thermal recovery ensures excellent air
quality and also makes optimal use of the heat in the outgoing air.” The ventilation system extracts used air from the kitchens and bathrooms, and uses it to temper the cool incoming fresh air
via a heat exchanger. More than 80 percent of the heat in the outgoing air can be used in this manner, which also means that a continuous stream of fresh air is always flowing into the house.

The heating system itself is so well hidden that one doesn’t notice it at first – it’s integrated into the windows. The inner pane of the triple-glazed windows is furnished with an extremely
thin and invisible metal coating which conducts electricity. When a low-voltage current is applied, the coating heats up like a resistance heater which enables the windows to radiate warmth. In
order to prevent heat loss to the outside, the outer pane has a heat-reflective coating. Moreover, the spaces between the three panes are filled with an inert gas that conducts heat less
efficiently than air. This quickly produces a pleasant interior atmosphere, and uses less energy than conventional heating systems. Window heating is not designed for long-term usage, however,
but rather for when outside temperatures are extremely low.

The Prospects
There are around 36 million residential units in Germany, of which about 24 million were built before 1979, i.e. before energy-efficient construction had entered general awareness. The huge
amounts of CO2 emissions that can be saved by simple insulation alone are clear from the following example. If a multi-unit older building that uses 25 liters of heating oil per square meter
per year is modernized down to a 7-liter standard, not only do the residents of an 80 square meter apartment save 1,440 liters of heating oil a year, they also reduce CO2 emissions by 4.6 tons
a year. Private households are responsible for around 14 percent of the total CO2 emissions in Germany, or a good 120 million tons per year.

Currently, the German Energy Saving Order stipulates maximum annual consumption limits of 7 liters per square meter for new buildings, and 11 for older buildings. The projects discussed here
demonstrate that we have the technical knowledge and conditions to do considerably better. As Karl Arenz notes, “Around 600,000 residential units are up for modernization every year. If all of
them were modernized to the 7-liter standard, we would save an additional 3 million tons of CO2 every year and nearly 1 billion liters of heating oil. Furthermore, this would also support the
job market.”

The Info Box
The 3-liter house pilot project

Luwoge launched its 3-liter house pilot project in Ludwigshafen’s Brunck Quarter in 2001, by modernizing a building from the 1950s into a low-energy house. It achieved this by means of
comprehensive thermal insulation with Neopor©, triple-glazed windows, a controlled ventilation system with 85-percent thermal recovery, and the latent heat storer Micronal© PCM.
Integrated into gypsum boards or wall plaster, latent heat storers absorb heat during the day to keep the apartment cool on hot summer days. The 3-liter house has since attracted considerable
attention and emulation worldwide, and its energy values have even exceeded expectations. Average consumption in the 3-liter house is 2.6 liters of heating oil per square meter per year.

Interior insulation for modernizing old buildings

Even buildings more than a century old need not continue to waste energy, as Luwoge showed by modernizing an old residential house in 2005. Built in 1892, this duplex in the BASF employee
housing district known as the Alte Kolonie now consumes only 6 liters of heating oil per square meter per year. Superior thermal protection measures were used to lower energy needs, with a new
generation of Neopor© plasterboard panels as interior insulation.

New 1-liter row houses

Luwoge has built 46 new row houses in the Brunck Quarter of Ludwigshafen. Here, too, the key to their energy efficiency lies in comprehensive thermal insulation. Neopor© panels up to 60
centimeters thick and triple-glazed windows filled with inert gas ensure that no heat is wasted. In addition a controlled ventilation system with thermal recovery is needed to achieve this. A
small block-type thermal power generator covers any additional heating needs for all 46 units, and provides the 1-liter house with electricity and hot water.