Energy Secretary Steven Chu has pointed to buildings as a key target for saving energy. On Monday, the Department of Energy backed him up with about $346 million in stimulus package funding.

The 81 million or so buildings in the United States use about two-fifths of the country's energy, more than manufacturing or transportation, the DOE says. About three-quarters were built before 1979, making them ripe for efficiency retrofits.

In the future, the DOE would like to see buildings built and operated as an "integrated system" with energy efficiency at the forefront, from design to day-to-day maintenance.

To that end, it set aside $100 million for "advanced building systems research," aimed at the goal of "net-zero" buildings that generate as much or more energy than they actually use.

That's something Chu has said could be accomplished, in part, through smarter software for controlling building HVAC, lighting and other energy-using systems. A host of energy services companies, or ESCOs, provide such services, and startups are coming up with both new technologies and new business models to improve on their offerings (see Making Building Automation Brainier and A PPA Model For Building Energy Efficiency?).

The DOE will also put $53.5 million into its "Commercial Buildings Initiative" launched last year. The money is to help expand the number of companies involved from 25 to about 73, starting in September.

To make homes and apartments more energy-efficient, the DOE is putting $70 million into job training for energy efficiency retrofits. And it will also direct $72.5 million toward "building and appliance market transformation," or that is, the technical and bureaucratic effort to do things like expand Energy Star rating systems and prepare builders and regulators for more stringent building codes.

Finally, the DOE will put $50 million into research into solid-state lighting at the technology and advanced manufacturing levels – in other words, more money for light-emitting diodes (LEDs). That announcement follows Friday's news of new federal lighting efficiency guidelines to take effect in 2012 for fluorescent and incandescent lights.