I installed an in-line duct fan to boost warm air upstairs, but I'm dissapointed in the fan itself- it's really loud, and it doesn't seem to be moving much air, even though it's rated for 250cfm. The fan is mounted behind the register in the ceiling above the stove room. From there the 6" flex duct goes approx. three feet into the upstairs bedroom. The brand is suncourt. Any suggestions?