Frank Gillis laid out four sheets of fiberglass inside the Penn College Building Performance Lab in Homewood.
With a knife, he demonstrated how to cut through the insulation layer, stopping short of the aluminum cover – “like filleting a fish” – and how to fold the sheet into a rectangular duct, attach it to other ducts, and seal it with staples, zip ties and pressure-activated tape.
His students, most of them experienced contractors, fanned out into groups and followed his lead, trading tips and needling each other on who could get the better seal…