The ParticipantsJohn Carmody: Director of the Center for Sustainable Building Research at the University of Minnesota in MinneapolisRoss DePaola: National Fenestration Rating Council–accredited simulator at WESTLab in Madison, Wis.Chris Mathis: Code expert and building performance consultant in Asheville, N.C.Stephen Selkowitz: Program head of the Building Technologies Department at the Lawrence Berkeley National Laboratory in Berkeley, Calif.JLC: Which is most thermally efficient for window frames — wood, vinyl, or fiberglass?DePaola: It's really about how the window is built, not the material. Vinyl is a budget material that's not as strong as fiberglass, so the frame material is thicker and usually has...

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