Oren wrote, on Sat, 30 Aug 2014 15:05:30 -0700:

Soffit vent. Likely every other vent (or three or four) at the
rafters.

Yes. I didn't know what a "soffit" was, offhand.

Googling, I see it's the "underside of an architectural
structure such as an arch, a balcony, or overhanging eaves.".

Those small rectangular "soffit vents" are all over the place
in each of the attics.