Recently I got my roof replaced. The contractor installed ridge vent at top. Before that I had gable vent on one side and an attic fan on the other side of gable vent (my central a/c-heating unit is in the attic). The contractor repeatedly said no need to cover the gable vents but just unplug the attic fan and not to run it. He says the gable vent infact helps air culation. Reading on line suggestions everyone says I should close the gable vent to avoid short-circuit. Any suggestions?
The powered fan will suck some intake air from the ridge vent..from the closest, easiest air supply. If you block the ridge, it may suck conditioned air from below, even back-drafting gas appliances (worse case). I feel if you cut power but leave it in place, the gables and ridge will act as exhaust if they are located more than 3' above the soffit (intake) vents. http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/bpn/57_e.pdf