2400 sq foot, single story, concrete tile on purlins roof, blown in
cellulose (?) insulation, well insulated 2x6 walls, Northern
California. Replaced the 25 yo heat pumps with AC/propane, huge cost
saving :-) . Have two dead 12" (or maybe larger) thermostatic roof
fans. How can I determine if there will be a payback on replacing
them? Obviously the air in the roof gets very hot, but by hand I don't
detect that the sheetrock ceiling is warm. Can I measure something
this coming summer to help me decide?