What’s the Difference Between a Register, Grille and Vent Cover?

We here at Pacific Register get the question a lot, and have even been guilty of using the terms pretty loosely ourselves.  So what do all of these terms mean that we throw around?


In general terms, a grille (or grill) is a protective cover designed to allow only certain materials to pass through. This could be an air grille in a passive ventilation system that’s designed to keep pests out but allow airflow, or a drainage grate that allows water to pass through but keeps out debris. When we use the term grille, we are referring to an HVAC grille that covers an air duct opening.

Vent Cover

A vent cover is an air grille that covers the vent or duct opening in forced air HVAC systems.  Usually vents are sized large enough to move the volume of air required in a room or building, and often a cover is needed over those openings in order to keep debris and other items from entering the system.

Air Supply vs Air Return

Heating and cooling systems are designed to recondition the air in a space, that means both pulling air into the conditioning unit or furnace, and then pushing conditioned air back to the desired rooms with fans and ductwork. Therefore, vents are usually classified as either a Supply or Return based on the direction of airflow.

Air Supply Vents

These are the most common vents in homes and commercial buildings, as many supply vents may be spaced around a room in order to efficiently heat or cool the space.  For example, an architect may want an air supply below each large window in a building in order to prevent hot spots in a room.  Supply vent openings are typically 4”, 6”, or 8” in width, but round and custom sized supply vent openings exist as well and we make covers for them all!  If you’re replacing a vent cover and are unsure if it’s a supply, you can turn on your system’s fan and hold a piece of paper against the vent to see if it’s pushing air out.

Air Return Vents

Air return vents are used by your HVAC system to pull air into a large duct that brings it back to the system where it can be heated or cooled and redistributed.  

There are typically fewer return air vents in a system, and the openings are usually much larger than supply openings. Returns decrease the air pressure in the room, and this larger size helps to balance the air circulation increased by having multiple, smaller air supply vents in a room. Air return grilles are usually designed to maximize free airflow, but it’s important that the openings aren’t large enough to permit any debris from entering the system.  Because of this, we find that a non-restrictive air filter is often desired to pre-filter the air returning back into the system to make sure no foreign objects enter the cooling and heating system.  Our decorative Filter Grilles and Frames are a popular option for holding and easily accessing air return filters.


A register, oftentimes called a heating register or AC register, combines an air supply vent cover with a device to control air at the point of supply.  The device to control air can either be a louver (to control air direction) or a damper (to control air volume). Along with our decorative grilles, we commonly supply customers with their choice of either louvers or dampers in order to make a complete Register.  


Louvers are used in air supply vents in order to control the direction of air flowing into a space.  They can either be fixed at a certain angle of deflection, adjustable, or even have individually adjustable blades to allow the user to customize the air flow specifically to fill a space or adjust for oddly shaped rooms.


Dampers are used in air supply vents in order to control the volume of air flowing into a space.  This allows a user to adjust a particular vent to reduce or maximize air flow.  Usually forced air systems require a certain amount of pressure in order to work efficiently and it’s recommended that dampers are never fully closed, but they make a great choice for example in rooms that get a lot of sunlight during portions of the year where seasonal adjustments to your system might be needed.

If you still have any questions about the differences between registers, grilles and vent covers, or if you need help selecting the correct grille, please reach out to us at info@pacificregister.com or call 805-487-7500. We are happy to help you find the right product for your home, office or project.

Additional Resources:

Frequently Asked Questions (FAQs) – Answers to our most commonly asked questions

How to Measure a Vent Cover – Step by step guide to correctly measuring for a new vent cover or grille