PORTLAND — Mike Lyne stood in the basement of Rosa True School on Monday, admiring the new boilers.

“This is the stuff I love,” he said, as he described the boost in efficiency to 90 percent in the 10-unit affordable housing development at 140 Park St.

On Tuesday, Lyne, the chief operating officer for Developers Collaborative, was able to celebrate more as the company publicly unveiled the renovated and expanded historic property it leases from the city.

“This could be the oldest rehab I have done,” Developers Collaborative principal Kevin Bunker said Monday.