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attic insulation - remove old "rockwool" or not?

chriskfos's Avatar

Join Date: Sep 2008
Posts: 1

09-28-08, 01:51 PM   #1  
attic insulation - remove old "rockwool" or not?

We have a 1926 colonial in the northeast. We want to add insulation in the attic to improve heat retention in the lower floors. There is currently about 2 inches of what we've been told is "rockwool" insulation (pebble like, falls apart when you touch it) in between the floor joists. It is not lined - i.e. no vapor barrier paper/foil.

Can we just lie batt insulation over the top of the old stuff? If so should we use insulation with or without a vapor barrier? If we use one with a barrier should the barrier go down against the old stuff or up into the attic?

Thanks for any suggestions.

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d00bs's Avatar

Join Date: Sep 2005
Posts: 195

09-28-08, 06:08 PM   #2  
I wouldnt even bother laying down fiberlgass. Just blow the needed levels of cellulose on top of all that. You will get way better airsealing and coverage by using it than with FG. Just be sure to check before for any and all obvious leakage points in the attic from the living space below and seal them up w caulk and or foamboard and sprayfoam. CHeck plumbing chases, tops of gable walls, open interior walls with no top plate, lighting fixtures, and chimney chases but use fire rated materials there. Keep the cellulose away from any soffit vents if you have them by using the styrofoam baffles.

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