A transfer grille is an opening with a fixed or adjustable louver that allows air to pass between adjacent rooms or spaces without installing full ducting. Transfer grilles are commonly installed in interior walls and door undercuts to facilitate return air circulation in residential and small commercial applications. These devices enable return air movement from bedrooms and offices back to central return plenums without individual return ducts.
Design and Installation
Transfer grilles are available in sizes ranging from 6×6 inches to 24×36 inches with adjustable blade dampers for flow control. They typically handle airflows from 50 to 500 CFM depending on grille size and static pressure. Standard materials include aluminum frames with extruded aluminum or plastic louvers.
Practical Applications
Transfer grilles provide cost-effective return air paths in residential zoning systems where separate returns are impractical. They are particularly useful in single-return systems where bedrooms and bonus rooms require adequate return paths. Building codes typically require transfer grille openings equal to at least 100 percent of the supply air volume to prevent room pressurization.