What began as a dream to make energy-efficient houses instead has become a way to keep pizzas hotter for home delivery.

Domino’s Pizza stores in Florida and elsewhere are among the first in the global chain to use high-tech hot bags, powered by “phase-change material” pioneered at the University of Dayton.

Domino’s believes the new bags give it a competitive advantage in the sizzling $25 billion U.S. pizza industry.

“We’ve always tried to be innovators of pizza delivery,” said Ralph Bower, vice president for Western Ohio Pizza Inc., the franchisee that operates 35 Domino’s stores in the Miami Valley, the third largest franchise in the world.

He said the bags keep pizzas 40 degrees hotter than conventional bags — so hot that his family once had to wait for a pizza to cool down after it had been in a new bag 20 minutes.

Domino’s has exclusive rights to use the bags, made by San Diego-based Phase Change Laboratories Inc., which licensed the technology from UD.

Phase-change material stores heat as it melts and releases heat as it freezes. The secret of the new bags is an electrically charged heat disk the size of a platter, which is slipped inside a new “breathable” bag. Drivers plug the disks into a bank of electrical sockets to recharge the disk between use.

The company will roll out a regional ad campaign featuring the new bags next month. A national marketing blitz hits in June. The new bags cost $90 apiece, six times the price of conventional bags. Domino’s is retrofitting all its stores with the bags and storage shelves at a cost of $4,000 per store. A spokesman said Lehigh Valley-area stores are using the new bags.

Domino’s selected Phase Change’s design because it keeps pizzas at 170 degrees and the new bags do not trap moisture, “So your pizza doesn’t get soggy,” Bower said.

Phase-change inventor Ival Salyer, a former UD senior scientist who’s now a private consultant, said his invention has found its way into other applications, including specialized coolers, food-storage trays, medical therapy products and even ear muffs.