can I put fiberglass insulation over rock wool?

Never have more than one vapor barrier or you will eventually get moisture trapped between them since barriers are not 100% effective.

Don Young

rock wool is contained in a plastic barrier - if I put the

so does that mean I cannot put fiberglass over the rock wool since it's encased in plastic? Do I need to rip it down? This is in a Cape Cod so the insulation is hanging from the gables. I'm just concerned that 3" of rock wool is not an efficient amount of insulation.

.> The rock wool is contained in a plastic barrier - if I put the

Just cutting slits will take care of it, remember slit both the top and the bottom.

The rock wool is contained in a plastic barrier - if I put the

slits at the top and the bottom are good enough to release the vapor? There are staples in the middle as well, should i put slits there too?

rock wool is contained in a plastic barrier - if I put the

They just did this on one of the home shows - Ask This Old House? There was already a moisture barrier, so they put fiberglass (six inch thick) crossways across the rafters with no additional barrier. The show was on in the past month or so.