Can batt insulation be applied over existing batt insulation without probems, especially with moisture?
Yes provided they do not have a moisture seal paper as an example .
Yes as long as its unfaced
The first layer is kraft paper faced up. I should have clarified that to begin with.
If you are in the Attic, Kraft face should be towards the warm side, then the other layer is installed perpendicular to the first layer.
This not the best I would prefer no craft papaer then having it installed that way.
If it was my home and I could get to most areas in the attic .
I would take the big fork you use to hold a roast tape it to a broom stick and then punch a few Like (15) holes per bat )
The existed painted ceiling is a pretty good vapour barrier .
Not only is this not the best, it is not good at all.
Moisture will get trapped in between the ceiling and the kraft paper.
The insulation was improperly installed to begin with.
Once that is rectified, then as Marcel said, place the new batts perpendicular. This will help reduce thermal bridges.
Knowing the insulation is improperly installed, you might want to also check the soffit vents to insure they are not blocked.
William, correct as you are in the vapor barrier trap, I believe that Roy’s method has been used in existing homes to negate the effectiveness of the kraft face vapor barrier so as to elliminate the necessitated removal of the existing insulation and still maintain it’s effectiveness as described above.
In comparison to a vapor barrier under a floor slab, that has not been lapped properly, taped properly and punctured all over from construction activities, it is rendered useless as a vapor barrier.
Thanks guys for the input.
The best way to achieve your goals is to go up in the attic and remove a section and throw it onto the other side. Air seal everything you can including gaps at the top plates. Put the insulation back properly and do the same to the next section. Once you get this done then add your new insulation and shoot for a grade 1 installation on both layers.