Three Ways to Beautify a Space with Grilles, Registers, and Diffusers
By Lukash Pruss, PE – When creating an aesthetically pleasing room, design considerations typically focus on flooring, surface finishes, and lighting. A critical room design element that is often overlooked are the HVAC grilles, registers, and diffusers—or GRDs. Every room served by the building’s HVAC system will have some form and combination of GRDs. In fact, GRDs are so commonplace that they typically blend into the background.
However, if the style and shape of the GRDs are not properly thought out, they can stick out like a sore thumb and be a blemish in an otherwise perfect room. Here are three ways to hide or incorporate GRDs in your room design.
Hide return grilles by creating reveals within soffits for the return grille to recess into.
Typically, these reveals are open to a plenum, however less common ducted configurations are also possible. Unless you’re standing beneath the reveal, the grille is hidden from view.
Another option is to create a reveal at the edge of a ceiling and leave the gap open to the ceiling plenum. This eliminates the need for a return grille and instead allows the return air to flow around the ceiling edge rather than through a traditional GRD.
It is important to properly size reveal openings to avoid issues with noise. If the opening is too small a whistling noise may be created by the air as it flows through the reveal or it could reduce airflow that may cause downstream issues with the HVAC system. Size reveal openings like this such that the air velocity through the opening is 400 feet per minute.
Incorporate GRDs in Building Elements
Building elements that provide a natural dead space is another great way to make GRDs seamlessly blend into a room’s design. For example, lobby spaces with exposed staircases often do not utilize the space beneath the staircase, which makes it a perfect spot for floor or wall return grilles.
There are also an emerging number of products today that integrate GRDs into other building elements such as ceiling fans or lighting. Light troffer diffusers, for example, are linear slot diffusers designed to attach to light fixtures to provide a seamless look. Notice in the image below how the supply diffusers appear to be just a normal border around the light.
Be Conventionally Subtle or Be Bold
It’s not always going to be possible to hide or incorporate GRDs in a room’s architecture. In these instances, it may be best to go with a visible yet subtle diffuser. Square plaque diffusers are a great option for blending into a ceiling while still offering favorable performance characteristics. The simple and smooth design makes these diffusers hard to notice unless you’re looking for them, especially in an acoustical tile ceiling application.
Conversely, you may want to use GRDs to help add a… twist to your room design. Radial twist, or swirl, diffusers are engineered to optimize air distribution effectiveness and are some of the most efficient diffusers on the market. These diffusers discharge a swirling air pattern and reduce stratification due to the effectiveness of the throw. By throwing the air further and more uniformly than most other diffusers, rooms are more efficient and kept at desired temperatures. Performance characteristics aside, these diffusers are sure to catch your eye.
A Word to the Wise
Taking an unconventional approach to airflow distribution requires that we pay special attention during the design of the system. Despite nice aesthetics, occupants will be unhappy in an uncomfortable room. A well-thought-out design ensures room air is thoroughly mixed, glazing is adequately air-washed, stratification is mitigated, and any noises associated with the system are acceptably quiet. With all these parameters to consider, it can be challenging to find the right solution. Collaboration between disciplines is key to finding a successful solution.
You don’t have to settle when selecting the right grille, register, or diffuser for a room; and your design doesn’t have to be boring! With some creative thinking and astute engineering, it’s possible to create new solutions for airflow distribution that enhance a room’s aesthetics while also keeping its occupants comfortable.
Lukash Pruss, PE is a mechanical engineer in the Morrison-Maierle Missoula office. He has a broad range of experience in HVAC and plumbing design for commercial buildings. In his free time, he enjoys outdoor recreation and gardening.
Technical review of this article provided by Eric Webber, PE.