The Austrian capital has one of Europe's most developed district heating networks, and the city wants to promote this method of heating homes, alongside renewable energies like solar and biomass.

Only buildings in areas where such alternatives are not considered feasible will be allowed to carry on using carbon-intensive methods, Birgit Hebein, Vienna's councillor responsible for planning, told reporters.

Officials say this will represent only 20 percent of new housing stock.

Vienna's population currently stands at just under 1.9 million but is projected to grow past 2 million by 2028, fuelling a property boom with 10,000 new housing units needed per year.

Hebein said the plans for new-builds would save 112,000 tonnes of CO2 emissions between now and 2030, "the equivalent of more than 1,000 car journeys to the moon and back".

Some 70 percent of new housing in Vienna is already connected to its district heating network, representing around a third of homes in the city as a whole.

While that network is itself not totally carbon-free, it is some 75 percent more energy-efficient than common alternatives, such as boilers, according to the Wien Energie operating company.