Fresh on the heels of announcing plans for a joint U.S.-Chinese clean energy research center, the Department of Energy has inked another research partnership with China on a matter close to Energy Secretary Steven Chu's heart – making buildings more energy efficient.

The memorandum of understanding announced Thursday between DOE and China's Ministry of Urban-Rural Development calls for the two to share expertise on efficient building technologies, including high-performance HVAC, insulation, lighting, cold storage, geothermal heat pumps, building-integrated photovoltaics and solar thermal systems.

That's on top of Wednesday's news that the two would commit an initial $15 million for the clean energy research center, focused on efficiency for buildings, clean vehicles, renewable energy and cleaner coal-fired power plants, including carbon capture and storage technologies.

Thursday's announcement also said that the two nations will look into a possible joint project in China to build green buildings, in support of China's "eco-cities" initiative, aimed at "integrated green cities that are sustainably designed, use renewable power and have efficient and modern transportation systems."

Chu has made building energy efficiency a focus of DOE's overall clean energy goals, and has highlighted China as a key partner in these efforts.

Last month at the Edison Electric Institute's annual convention in San Francisco, Chu floated some ideas for how the two countries could work together on building efficiency, including the idea of co-developing an open-source software platform for better building automation systems (see Making Building Automation Brainier).

Buildings use about 40 percent of the energy generated globally and generate nearly half the world's greenhouse-gas emissions. But DOE believes that could be cut by at least 30 percent through efficiency retrofits and better-designed new buildings – and Chu, in a Thursday prepared statement, said the long-term goal "should be buildings that are 80 percent more efficient."

Together, China and the United States are responsible for about two-fifths of the world's greenhouse-gas emissions, and China recently surpassed the U.S. to become the world's top emitter. With its dependence on coal-fired power generation, China will have to make big strides to reduce its energy-related greenhouse-gas emissions to move the planet toward an overall reduction in global warming.

Given that China is expected to build the equivalent of the United States' entire building stock in the next 15 years, according to DOE, it's a market worth focusing on, say Chu and others in the green building industry (see Green Building Entrepreneur: Build Green or Face Catastrophe).

Making buildings more energy efficient is a broad-ranging industry, including makers of cleaner building materials, those using more efficient construction techniques, developers of energy efficient HVAC and lighting systems and building automation software and system makers. It's a mix of established players, startups and deep-pocketed entrants to the field like IBM and Cisco Systems (see Green Light post and Cisco Rolls Out Building Management 'Mediator').

The Chinese opportunity is not going unnoticed by the bigger players in the industry. U.S. utility Duke Energy is working on developing deals with Chinese companies on renewable energy, smart grid and cleaner coal-fired power generation projects (via Wall Street Journal's Environmental Capital blog).

And IBM has projects underway in China related to building energy efficiency systems and smart grid efforts, according to Michael Valocchi, lead energy and utilities consultant for IBM's Global Business Services division.

But protecting intellectual property could be a concern for U.S. companies seeking Chinese green business opportunities. The U.S. Chamber of Commerce in May formed a coalition aimed at protecting IP on clean energy and other technologies in the context of global cooperative research such as that the DOE is championing in China.