The return air must have a clear path back to the air handler from every room that has a supply outlet, with the exception of bathrooms or kitchens due to the potential for spreading odors through the house ( Burdick 2011). A well-designed return air strategy is critical for the performance of the HVAC system in an energy-efficient house, which may have lower airflow requirements to meet the lower heating and cooling loads ( Burdick 2011). Pressure imbalances can also cause the furnace and air conditioning equipment to work harder than necessary. Inadequate return air pathways can cause pressure imbalances from room to room, which can cause drafts and temperature differences between rooms or floors, leading to comfort complaints. See the Compliance Tab for related codes and standards, and criteria to meet national programs such as ENERGY STAR Single-Family New Homes, DOE’s Zero Energy Ready Home program, and EPA’s Indoor airPLUS.įor central “forced air” furnace and air conditioning systems to operate properly, the HVAC distribution system should be designed with adequate supply and return registers to provide conditioned air to all parts of the house and return stale air to the furnace for reconditioning. Test the pressure differential with the bedroom doors closed.Seal all seams, gaps, and holes in the ducts and connections. Ensure that both openings have the required free area. If a balancing report was not provided, the flow of the supply register when the air handler is on high speed may need to be measured using a flow hood, anemometer, or other flow measurement tool. If transfer grilles or jump ducts are used, refer to the balancing report provided by the HVAC contractor for the bedroom air flows to size the grilles or ducts.A rater-measured pressure differential of ≥ -5 Pascals and ≤ +5 Pascals (0.020 inch water column) is acceptable for rooms with a design airflow ≥150 cfm.
ENERGY STAR Single-Family New Homes requires that the dedicated return ducts, transfer grilles, jump ducts, and/or door undercuts together achieve a rater-measured pressure differential of ≥ -3 Pascals and ≤ +3 Pascals (0.012 inch water column) with respect to the main body of the house when bedroom doors are closed and the air handler is operating on the highest design fan speed.Install ducted returns or a combination of ducted returns, transfer grilles, jump ducts, and/or door undercuts in bedrooms to allow pressure balancing between bedrooms and the rest of the house in homes with ducted heating and cooling systems by providing a path for room air to return to central air handler thereby increasing the volume of conditioned air circulating in the room.Jump ducts are also commonly referred to as jumper ducts or crossover ducts. Provide for pressure balancing between bedrooms and the rest of the house, using jump ducts or another means.
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