From the responses given in the “Miscellaneous” section about “attic insulation” comments in reports, it’s obvious that most HI’s have not studied or grasped the idea of airsealing for energy conservation purposes.
In an attic before adding any/more insulation, airsealing MUST be done. As insulation levels of up to R50 will be installed, this most likely will be the last time attic efficiency will be addressed, so do the airsealing; no one is likely to go back into the attic at a later date to lift up batts or dig through blown insulation to airseal.
Fiber insulations do slow down air movement (infiltration/exfiltration) a bit but this is not a solution! With a poorly done job (insulated but not airsealed), you will actually be encouraging/creating a condensation problem. The heat loss by conduction to the attic space will be significantly reduced resulting in a much cooler/cold attic but upward air exfiltration is only slowed down a bit.
Above the attic insulation, this interior warm moist air is now cooled below its dew point and is looking for a cool/cold surface to condense on- attic framing and sheathing. Now we have a problem that most likley did not exist before the insulation was added!
So we then have to add more attic ventilation to try to solve the condensation problem that could have been prevented by airsealing before the insulation was added or upgraded.
AIRSEAL! AIRSEAL! AIRSEAL!