…that one thing would be to air-seal the floor of the attic…
Homeowners ask me this question all the time. The reason I suggest sealing the attic floor is because it’s not too difficult and it makes sense. Heated air has a tendency to rise, and this can create pressure just underneath the floor of the attic. If there are leakage points here, then conditioned air will be forced into the attic, also pulling in an equal amount of un-conditioned air from some other leakage points lower in the structure. Sealing the floor of the attic eliminates this cycle.
The National Negawatt Exchange 