Mineral wool wraps are the most affordable and effective insulation for crawl space ducts. They are easy to cut, last for a long time, and healthier for humans. Meanwhile, fiberglass wraps are cheaper but more hazardous and difficult to handle. If you do choose to use a fiberglass wrap, make sure you are wearing long sleeves and wear proper protective gear.

If you have blown-in insulation, using an insulation vacuum will quickly and easily suck up all the insulation. Many come with built-in HEPA filters for added safety. While some people suggest breaking up large batts and feeding them into the vacuum, this can expose you to more fiberglass fibers. With batts and rolls, carefully removing them and placing them into garbage bags is a better process.

It's essential to use insulation materials specifically designed for air ducts. Common types of duct insulation materials include fiberglass, foam board, and reflective foil. These insulation materials have the right properties to withstand the temperature and airflow conditions within the ductwork. Using the appropriate insulation not only ensures efficient temperature control but also prevents potential safety hazards or the release of harmful particles into the air.

R-30 insulation is better for higher thermal resistance, but whether it’s "better" depends on the application. R-30 is much thicker and suited for areas like attics or floors in cold climates, where more insulation is required. R-13, on the other hand, is thinner and works well for 2x4 walls or milder climates where less insulation is sufficient. Choosing between R-13 and R-30 depends on the area being insulated and the climate. For example, R-30 provides more insulation but may not fit everywhere in your home.