Identify supply and return openings
Supply registers deliver conditioned air; return grilles allow air back into the system. Keep furniture, rugs and curtains from blocking either. A decorative cover should be suitable for the opening and its airflow needs. Replacing a grille changes its appearance, but does not automatically correct an underlying duct issue.
Measure before buying
Record the duct opening dimensions and the mounting location. Faceplate dimensions can be different from the size used to identify the product. Note whether the cover is for a floor, wall or ceiling and whether a damper is appropriate. Ask for help if the opening or existing cover appears damaged or unsuitable.
Avoid solving one room by restricting another
Closing large numbers of registers or adding filters at outlets can affect system airflow. A persistently hot or cold room deserves a review of duct delivery, return-air paths, insulation and other building conditions. Tell Comfort Nest when the problem occurs and whether it changed after renovations. Ask about compatible accessories and whether an airflow assessment is the better first step.