In my basement utility room there is this flexible insulated duct. It runs to a vent in the siding outside. The duct is not connected to anything in the basement. It just hangs there. I asked a few people what the purpose of this is and didn’t get an answer. Even asked the last HVAC tech that was here what it was for. He thought maybe an old return air duct that goes outside but that didn’t make sense since there already is one of those. The furnace here is gas and has a dedicated pipe that runs outside to pull air. So what is this? Does it have something to do with the house having gas lines for the dryer and stove?