LEICESTER, England — The Mark Group started hunting for a new untapped market when it realized that its core business — insulating old homes using innovative technology — would drop off in coming years. Based in this rust-belt city, the company had grown rapidly over the last decade largely because of generous and mandatory government subsidies for energy conservation that impelled the British to treat their homes.

But as a result of those incentives, market saturation was nearly complete — more than 80 percent of the country’s older homes had been at least partly retrofitted by 2010, the company estimated. So the Mark Group recently opened its newest office in another country, one with a relative paucity of expertise in the company’s specialty of cutting home energy bills and greenhouse gas emissions.

The office is in Philadelphia.

“The United States was a nearly untouched market with 120 million homes, most of them very energy-inefficient — it was a massive opportunity,” said Bill Rumble, the company’s commercial director, who had recently returned from its new American headquarters.

Many European countries — along with China, Japan and South Korea — have pushed commercial development of carbon-reducing technologies with a robust policy mix of direct government investment, tax breaks, loans, regulation and laws that cap or tax emissions. Incentives have fostered rapid entrepreneurial growth in new industries like solar and wind power, as well as in traditional fields like home building and food processing, with a focus on energy efficiency.