I have a high efficience two stage furnace. There is a fresh air vent in the room with the furnace. It is a large insulated flexible duct that runs from an exterior vent, down from the cieling and directly beside the furnace. Does this vent need to be that close to the furnace or does it suffice to have a fresh air vent in the same room as the furnace? If I remove most of the duct and simply put a grate on it, will that affect the efficiency of the furnace?
Answer:
Rather than fitting a grate onto it, a bucket or some such should be placed under the furnace combustion air duct to prevent cold outside air from spilling directly onto the basement floor. The bucket would have air at closer to room temperature by the time it turns a complete 360 degrees and enters the basement.
