Any uses for tar paper from fiberglass insulation?

Question

I installed some fiberglass insulation over some old celluose so I removed the vapor retarder that came with the fiberglass. Can I use it for anything (the vapor retarder) I notice some of the ductwork in the house was wrapped in insulation with the vapor barrier on the outside and some of it was deteriorating. Can I slap the new vapor barrier over the old stuff or is that a bad idea?

Answer 1

I really don't know why you went to the trouble to remove the vapor barrier. It is there for a reason. It also helps to insulate.
Yes, you can use it to rap old duct insulation. You sure make a project a whole lot more difficult. But whatever floats your boat -smile.

Answer 2

You added insulation to the attic; removed the vapour barrier from the insulation batts you added.

If the above statement is true, you were right to remove the vapour barrier. Vapour barriers are to be installed in the warm side of the wall, ceiling, or floor.

You do not want double vapour barriers. You can put up to about 30% of the insulation outside the vapour on the inside of the vapour barrier. Example: R20 on the cold side of the vapour barrier; R 6 on the warm side of the vapour barrier.

If you have too high of an R alue on the warm side of the vapour barrier, condensation will form on the warm side of the vapour barrier and will not dry out properly. This will cause rot, mold and many other problems.

If the heating duct is in the heated area of the house, installing a vapour barrier on the outside of the duct is OK.
As for using the vapour barrier which was removed from the batts you installed over the celluose on the heating duct, It will be better to cover it with a 6 mil poly film instead. Tape the joints with Red Tape meant for vapour and air barriers.

If the heating duct is in the actic and/or in an unheated area, do not put the vapour barrier on the outside of the duct insulation. The exist vapour barrier may have bee damage on purpose and just appears to be deteriorating.

Hope this helps

Good Luck