A vent damper will not help as much if your furnace is located in an unheated space.

The purpose of the vent damper is to help prevent off-cycle heat loss. Yet if your furnace is located in an unheated part of the house, it won’t do much good. That’s because a large proportion of the heat trapped in the flue by the vent damper will simply pass out into the relatively colder air of the room. If the furnace is in a heated room, this temperature differential will be much smaller, and so the heat exchanger will be able to capitalize on a greater amount of thermal energy.

If you have any questions, contact an expert in heating or dryer vent cleaning in Hawaii.