Duct work covered with this

This home was built in 1961. What is this covering on the duct work.

Paper discolored by heat

I concur…

Doesn’t look suspicious to me.


HHMMMM!! In Florida. Does this HVAC system have A/C? If so, could it be an insulation covering with an asphalt based exterior vapour barrier to prevent moisture condensing on cool duct surfaces in humid wether?

Looks like an asphalt coating to me. How hot would heating air have to be to discolour paper that much? 300-400 deg F…the high limit should’ve shut it down way before that point!!!


I did not think I would have to spell it out word for word he did say 1961.

Heat over time = discolored paper see it all of the time

Yep, Same here.

Gary: Is there insulation under the paper covering the ductwork?