Product review (5 stars): saves heating bill; adds moisture
Had this item for about 4 years.  Every winter we connect it to the dryer duct to re-direct the dryer heat inside.  Our dryer is in the mud room of the first floor and there is some moisture condensation for the beginning of the cycle but the dampness is useful to counter balance the dryness from the forced hot air from our home's heat pump.  We make sure the connections are secure because sometimes extra lint or dust can escape.  Also, we use an old pantyhose around the box as another filter to catch more lint.