My daughter has an older home with what I call "rock wool" insulation in the ceiling and walls. How to better insulate?

Asked by Kenneth Kempf
Hillsdale, IL

The walls can be easily re-insulated by removing the falling wool and replacing with R-13/19. What to do with the ceilings with no vapor barrier? Remove the old wool and replace with R-50 or cover with additional fiberglass and not worry about a vapor barrier? There is a wooden subfloor over a lot of the ceilings so removal may be difficult or for workaholics to re-install.


Danny Kelly

Answered by Danny Kelly

Charlotte, NC

Kelly McArdle Construction

August 30, 2010

Your best bet would be to:

  • Remove subfloor in attic
  • Air seal at ceiling level around all wall intersections, top plates, plumbing and wire penetrations and any other gaps that are up there
  • Fir up existing ceiling joists to ensure a proper depth on insulation can be installed
  • Install new insulation -- blown fiberglass or cellulose
  • Reinstall subfloor

I would not be concerned about the lack of a vapor barrier -- new research has shown that they actually do more harm than good.

For more information:

Read Lily Livingston's Q&A "Doesn't sprayed cellulose insulation tend to settle, leaving areas in the wall where there is no insulation?"

Tagged In: insulation, vapor barrier, ceiling insulation

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