Top and bottom if you want convection currents to circulate air.
so true!
I usually open the bottom windows on one side of the room and the top on the other side to create currents to pull out the hot air.
and the method works best in a multi-story house where you'd open the top section of windows on the upper floor(s) and bottom section on ground floor.
as heat rises, cooler air will be drawn in to the lower windows and create a nice draft through the house.
in 19th century Gulf (Plantation) architecture an early method of air conditioning was the installation of a cupola at the apex of a central staircase. a gas ring was installed encircling the interior of the cupola that, when lit (like gas lamps) would create a hothouse effect in the cupola forcing a rush of air out of the venting lites and drawing cooler air in through large open (screened) doors on 3 or 4 sides of the house (which were usually well shaded under a deep porch.
