perfect balance indoor return air pathway

Ensure that both openings have the required free area. If door undercuts are used, pay attention to the door material.Seal all seams, gaps, and holes in the ducts and connections. Test the pressure differential with the bedroom doors closed.For hollow doors, you may not want to undercut or you might need to provide a bottom support after making the undercut, as the typical bottom supports are roughly 1 inch tall. See the Compliance Tab for related codes and standards, and criteria to meet national programs such as ENERGY STAR Certified Homes, DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and EPA Indoor airPLUS.ĭoor undercuts are a commonly used method for pressure balancing between rooms (Figure 1) but they are not a recommended approach as they do always provide an adequate return air pathway for HVAC systems. Seasonal changes in wood can result in variations in the height of the door undercut opening. Changes to the flooring material, such as adding carpet, can obstruct the return pathway. The ENERGY STAR pressure-balancing thresholds are difficult to achieve with just a door undercut for most applications, except for rooms with minimal supply airflow (<20 cfm). In most applications, the door undercut would need to be 1.5 inches or greater to allow enough air to pass. There are some through-the-door alternatives that can be effective. Consider installing a transfer grille in the door or employing another return air pathway method, such as transfer grilles or jump ducts. The video on the Training tab shows one of these options, transfer grilles.

To determine if an adequate pathway exists for air to return to centrally located returns, the following room-to-room pressure measurement can be used:įigure 1. Door undercuts are commonly used to provide a return air pathway from rooms with closed doors.Using a manometer, connect tubing to the input port.The reference port for the differential pressure measurement can remain open.While standing in the center of the house or hallway, place the tubing from the manometer under each door and record the pressure difference from each room with respect to the main body of the house (note the presence of a negative or positive sign).The bedroom will typically be pressurized (positive) when the doors are closed.

ENERGY STAR requires that rooms should not be pressurized or depressurized by more than 3 Pascals for any room being supplied with less than 150 cfm of conditioned air.If the supplied airflow to a room exceeds 150 cfm, a threshold of ≤5 Pascals is required. These are good metrics to strive for regardless of whether or not pursuing ENERGY STAR certification.ĮNERGY STAR Certified Homes, Version 3/3.1 (Rev. Duct Quality Installation - Applies to Heating, Cooling, Ventilation, Exhaust, & Pressure Balancing Ducts, Unless Noted in Footnote.Ħ.2 Bedrooms pressure-balanced (e.g., using transfer grilles, jump ducts, dedicated return ducts, undercut doors) to achieve a Rater-measured pressure differential ≥ -3 Pa and ≤ +3 Pa with respect to the main body of the house when all air handlers are operating. Test configuration and an alternative compliance option in Footnote 34. 34įootnote 34) Item 6.2 does not apply to ventilation or exhaust ducts.

When verifying this requirement, doors separating bedrooms from the main body of the house (e.g., a door between a bedroom and a hallway) shall be closed and doors to rooms that can only be entered from the bedroom (e.g., a closet, a bathroom) shall be open.įor an HVAC system with a multi-speed fan, the highest design fan speed shall be used when verifying this requirement.

Perfect balance indoor return air pathway