U225X / ENGINEERING UNWARRANTED
Ceiling-fan and box-fan airflow strategy
Public record / FIX-012 / Revision A
PUBLIC RECORD
U225X
U225X
The recovered conversation identifies the unused attic/whole-house fan as a major heat-leak path. The recommended approach is a removable insulated cap made from 2-inch R-10 foam board, sized a few inches beyond the opening, with compatible foil HVAC or foam-board tape and weatherstripping around the contact edge. The cap must remain removable and the fan must be unable to start while covered.
TECHNICAL NOTES
Recovered attic-fan heat-barrier plan for an unused whole-house fan, plus an airflow caution for box fans near supply registers.
SPECIFICATION
BarrierRemovable 2-inch R-10 foam-board cap
SealCompatible foil HVAC/foam-board tape
Contact edgeWeatherstripping
FitA few inches beyond the opening on all sides
StatusRecovered plan / dimensions still to verify
DEVELOPMENT HISTORY
2026.09.06ARCHIVE-01Recovered and summarized from the supplied Attic Fan Heat Barrier conversation; raw transcript remains unpublished.
2026.09.01Rev AInitial manifest record created from the topic index.