Most people don’t think much about their HVAC system’s outlets.
Not until there’s an HVAC problem. When that happens, you’ll probably care more about getting your HVAC system running again than understanding the different kinds of air vents out there.
But understanding the difference between air vent types can help you diagnose and fix problems easier. And if you’re installing or renovating an HVAC system, you’ll be better equipped to design the best system that works for you.
Vents, grilles, floor registers, diffusers—what do all these air outlet terms mean? Let’s take a look.
“Vent” is an umbrella term for any intentional opening in your house’s ductwork. Floor registers, grilles, and diffusers are all a type of vent. Vents are almost always located inside your house.
HVAC systems often have a large outdoor component—usually an AC cabinet containing a compressor and a condenser. Though these components do plenty of work on hot days, they don’t pull air in or push it out. Instead, most HVAC units maximize their efficiency by cooling and heating air as it circulates throughout the house.
Because HVAC units rely on this “closed system” design, proper ductwork and proper vent placement are both essential.
Your HVAC system may still have an outside vent. Many furnaces use outdoor vents to blow out their exhaust and intake fresh air. These airflows, however, are usually separate systems from the air circulating in a home’s ductwork.
Floor registers have a mechanism that gives occupants some control over how much air flows through the vent. That mechanism is usually a simple lever or a wheel.
Floor registers are so-named because they’re usually near the bottom of the wall or on the floor itself. That makes it easy for occupants to adjust the flow. However, arranging furniture to avoid blocking them can be difficult.
If you prefer a high-tech floor register, some manufacturers make “smart” models. These registers can automatically change airflow based on temperature, air pressure, and user input. They tend to be more expensive than manual registers and require a power source.
It’s important to note that closing a register is usually not enough to seal it off from the house’s HVAC system. Air will still flow through the closed register—just not as much air.
A common homeowner complaint with many HVAC systems has to do with vents blowing out cooled or warmed air. The complaint goes like this:
A room’s vent blows out air, keeping most of the room at a comfortable temperature. But whoever stands right by the vent gets an uncomfortable blast of hot or cold air. In a large room with many vents, there may be many spots subject to unpleasant temperature extremes.
Diffusers address this complaint. As a blast of air goes through a diffuser vent, the diffuser disperses it to a more gentle flow spread across a wider area. Everyone enjoys a comfortable temperature, with no one stuck in a hot or cold zone.
Diffusers are common in larger rooms because they can cover more ground. They’re often installed in ceilings to maximize their range.
That means you need ductwork in your ceiling, not just your walls, to install one. To maximize their spreading area, some diffusers protrude slightly from the wall or ceiling.
Grilles are the simplest kind of vent. They’re grates, mesh, or other vented openings connecting rooms to ductwork.
Unlike floor registers, they have no airflow controls. You can only stop air from flowing through a grille by covering it or severing the attached duct from the HVAC system.
Grilles can be anywhere in a room, including on the ceiling. That makes them easier to place. No moving a sofa to accommodate a floor register when you can put a grille above it, instead!
Some grilles only vent air out, much like floor registers. Others (called return grilles) intake air for recirculation through the HVAC system. Maintaining proper air intake flow is crucial to your entire HVAC system’s health.
Because return grilles handle so much of the home’s airflow, many homeowners install air filters in them. Air filters can improve the home’s air quality. However, they can stop filtering and clog ductwork without regular cleaning.
Which should you choose: a floor register, a grille, or a diffuser? Where should the vent go? There are several factors to consider.
Floor registers and diffusers have design limitations: one needs to include a control mechanism, while the other needs to disperse air. Because of their simple design, grilles have a broader aesthetic range. They can be as simple as a few bars or feature ornate ironwork.
HVAC Unit Health
Some HVAC professionals advise against closing floor registers too frequently.
That’s because your HVAC unit is (hopefully) appropriately sized for your home. Closing and opening registers affect your HVAC unit’s area of effect, which can overwork components of your AC or furnace system. This is especially a concern with smart vents.
To counter this, size your HVAC unit appropriately, and don’t keep too many floor registers closed at once.
Blocking a vent doesn’t just impede the airflow in your home. It can also damage the object (e.g., a carpet) covering the vent and even cause a fire risk. If you want to cover a vent, use a register mechanism or vent cover designed for that purpose.
A vent placed on residential floors will likely get walked on. You may need heavy duty floor registers or grilles to support an adult’s weight. You should also consider whether floor register levers may snag clothing or stub toes in certain locations.
Pets and Children
Pets and small children spend a lot of time near the ground, and their small paws and fingers are more likely to get hurt in a vent than an adult foot. An HVAC expert can help you child-proof your vents.
Educate Yourself for Your Best HVAC System
Most people think about their AC or heating units first when they think of the best HVAC system for them. But many other components—including the right arrangement of floor registers, grilles, and diffusers—are key to making your HVAC work for you.
So if you’re looking to fix, renovate, or install a new HVAC system, education is key. Look through our article archives to learn more about HVAC systems.