What are the "cleanest" materials for a fresh-air intake duct?

— Brian Trenton, NJ

Answered by Scott Collins on June 17, 2010

Do we still need ductwork in a passive home?

— Ihab Riad Prospect Heights, IL

Answered by Erik Henry on May 19, 2010

What's the best way to seal a 30-year-old AC duct system in an attic?

— Glenn Summers Melbourne, FL

Answered by Andrea Foss on March 23, 2010