Andreas Knoch clambers up the scaffolding of a newly constructed two-story building in the German capital.
On the roof, the engineer points to a double row of sleek solar panels lying flush with the shingles. The panels will provide future residents with 60 percent of their hot water.
"On a day like today the collectors probably wouldn't be working," says Mr. Knoch as he scans the gray November sky.
But he adds, "An overcast sky is not always overcast," since even on cloudy days solar radiation can be high.
For 10 years Knoch's engineering firm AKUT has specialized in environmentally friendly technologies, pioneering the practical applications of solar power.
Now his experience could be in greater demand, since Berlin's construction industry recently committed itself to installing solar collectors in 75 percent of all new buildings.
Although not formally part of the government's goal of reducing carbon dioxide (CO2) emissions by one quarter by 2005, the industry's plan aims for a similar reduction through better insulation, energy conservation, and solar power.
Two years ago the Berlin legislature passed an ordinance setting ambitious guidelines for solar-power use. The city government never put the ordinance into effect however, and critics charge that the construction lobby stalled long enough for a building boom following German unification in 1990 to pass.
The industry, for its part, claims that the voluntary commitment will outdo the legislature's proposal. If, after five years, the construction industry does not attain its CO2 reduction goal as well as the installation of 4,200 square yards of solar collectors, the 1995 solar ordinance will take effect.
"The [city] government wanted a partnership not to irritate industry but to cooperate with it," says Rita Neise of the Berlin Chamber of Commerce, a signatory of the industry initiative.
She defends the "integrated solution" of the initiative, which focuses on solar energy as a means of energy conservation rather than a goal in and of itself.
In the past, the German capital has been at the forefront in promoting solar energy. A combination of subsidies from the government and the city's power company provided up to 60 percent of the funding for solar-heating projects.
According to Berlin's Department for Development, Environmental Protection, and Technology, the city's photovoltaic cells have a capacity of 1 megawatt. That's enough electricity to keep about 200 households running for a year.
Despite such support, Knoch says "the market is subject to strong fluctuations." He explains that while subsidies have created an appetite for alternative energy, Berlin's budget constraints and the lack of a strong solar lobby make for an unstable market.
One unattractive aspect of solar power is that it is more expensive than traditional energy sources. But Knoch notes that if costs to the environment were calculated into the price of fossil fuels, solar energy would look cheaper by comparison.
While his firm is a potential beneficiary of the construction industry's voluntary initiative, Knoch says he would have preferred the government ordinance, since it would have explicitly required solar installations in public buildings and single-family homes.
Others are more critical. The local Green Party complains that the initiative is not legally binding, and that it consists of measures builders have already implemented.
"I wish there would be more trust," says Ms. Neise of the Chamber of Commerce.
She adds, "Among the critics are those who don't recognize what industry has done for the environment."
These are not empty words in a country where high environmental awareness has forced industries to adopt a green image.
According to a recent study, German industry has reduced CO2 emissions by 46.5 million tons since 1990, or three-quarters of its targeted goal.
In a further boost to the domestic solar industry, the German government and the energy industry announced earlier this month the construction of two factories that will annually manufacture photovoltaic cells with a total capacity of 38 megawatts, one-third of current production worldwide. In anticipation of the new technology, the state of North Rhine-Westphalia has dubbed the region "Solar Valley."