BEIJING -- China will demand new buildings in cities achieve mandatory energy-saving standards and renovate existing buildings to make them greener by 2015, the country's top economic planner has said.

The standard of green buildings, which are resource- and energy-saving and environmentally friendly, will be adopted on all government-invested buildings from 2014, said an official with the National Development and Reform Commission, who declined to be named.

As of 2014, the standard will also be applied to affordable housing projects in the four provincial-level cities, provincial capital cities and the five cities at the vice province level as well as to public constructions with an area of more than 20,000 square meters in a single building, said the official.

It takes an extra cost of only 50 yuan ($8) per square meter to meet the minimum requirements for green buildings, compared with common buildings, according to the official.

Renovations will be carried out on urban buildings to improve the efficiency of their heating systems.

China aims to construct 1 billion square meters of green buildings during the 2011-2015 period and make green buildings account for 20 percent of all new buildings in the country's cities in 2015, according to a government plan.