Share 'Insulating rooftop ducts with spray foam - retro - hot/dry climate'

Here in Tucson, AZ we have a lot of ducts on the rooftop. This is because many older homes are flat roofs and only had swamp coolers when they were built. This leaves no other place but the roof to install ducts for AC. Many of these ducts were never insulated. Many homeowners do not want to replace whole duct systems just to insulate on the inside of the duct - for obvious cost reasons. They alw…