The key to designing environmentally friendly ductwork is leak reduction, which starts by picking the right ducting materials at the installation stage. Galvanized steel ducting is far less prone to leakage than flex ducting.
Difficult-to-clean flex ducting is more likely to leak than other ducting materials, which can lead to reinstallations and environmentally costly repairs. If flex ducting is necessary, it should be reserved for short runs in trunk-and-branch duct systems.
Standard in the HVAC industry, Manual D is the software used to produce the most efficient and environmentally friendly ductwork designs. This software is published and guaranteed by the Air Conditioning Contractors of America. Ductwork designers use this software to make important decisions about duct width, which duct attachments to use and overall ducting layouts. It is generally advisable to keep all ducts as short and as straight as possible, and to avoid routing ductwork through unconditioned zones such as attics and crawl spaces. Designers should fasten ducting junctures with screws instead of press-fitting them together.
Finding and eliminating leaks is important for maintaining any type of green ductwork design. The average homeowner loses hundreds of dollars per year due to environmentally damaging ductwork leaks. Aside from holes, poorly sealed duct connections are the major source of leakage. Leaks are commonly found where ducts are connected to grills and vents.