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wrote in message ...

I like Grainger's $73 4TM66
3-speed 16" reversible window fan with thermostat, which moves 5850 cfm
with 90 watts on the highest speed.

thats way cheap. I've been looking at 9"/12"ers at £100, about 150usd,
and 550cfm.

But more importantly most fans dont seem to have dB ratings, and that
is a real issue considering the fans would be above bedrooms and run
at night, and mounted on a springy PB ceiling.

Doing that well may require 2 fans, one to move outdoor air through the
house and another ceiling fan to mix it around in the house. The outdoor
air won't cool much mass if it just passes through the house in a compact
stream. It's also nice to have moving vs stillish air near the mass
in order to raise the surface airfilm conductance.

Thats my #1 concern here. A WHF will move air through the already
coolest parts of the house, but not through the rooms where cooling is
needed most. Not sure how to address that. Would still be a benefit
though, and much less cost than multiple fans.

Regards, NT