Has anyone used a product called Reflectic duct wrap. Reflective silver on both sides with bubble wrap insige says has R value of R8. Can this also be used on main trunk on outside even though has insulation on inside. I,ve been having problem with duct sweating espicially main trunk. All duct runs thru crawlspace. I know between the humidity and the cool on main truck it will get some condensation but this stuff is supposed to stop the sweating?