Return Air Floor Duct

An air return duct is basically a concealed air passageway in a home or other building that acts as a channel for pumping air out of an enclosed room and into the air conditioning or central heating system these ducts typically start with vent grates in the wall on the ceiling or in the floor.

Return air floor duct. The illustration above shows a floor joist cavity used as a return air duct by nailing material such as gypsum. A return air duct is what carries air back to the furnace after it is dispensed throughout the home through the supply duct. Using floor joists as return ducts by panning can cause leakage because negative pressure in the cavity will draw air from the outside into the cavity through the construction joints of the rim area at the end of the joist cavity. Return air ducts usually use ceiling joist spaces as the actual duct.

Without a return air duct the air would not properly circulate and your energy costs would rise. Yet field measurements in typical homes indicate that second floor return air ducts relying on building cavities for air transport are often so leaky that they returned little air to the hvac blower. Imperial 4 in x 300 in insulated polyester flexible duct. The single giant return air grill in the floor balances the load at the furnace motor but does nothing to promote cross ventilation in each room.

It s much better to put a return air duct in each room. Here s an example of a giant return air grill near the floor.