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How to size supply and return air grilles correctly

The ductwork’s in stellar shape, your filters are clean and consistently replaced, and your HVAC unit is impeccably maintained. But if your supply and return air grilles aren’t sized correctly or are facing in the wrong direction, all of your upkeep is wasted.

This is because both return and supply air grilles play an integral role in air circulation and overall efficiency — one incorrectly sized grille could be the difference between comfort and discomfort. To ensure you enjoy healthy, clean air in a comfortable environment, here’s how to size supply and return air grilles correctly:


Step-by-step guide on how to size supply and return air grilles

  1. Measure the hole in the wall (don’t make the mistake of measuring the size of your old grille).
  2. Always measure the width first, followed by the height — you don’t want your louvers facing in the wrong direction!
  3. Unless you select a square grille (such as a Cube Core with an Eggcrate design), the size of the hole in the wall will not be the size of the grille you need. This is because a frame’s outer dimension adds roughly 2 inches to the overall size.
  4. For example, a 14x12 inch supply or return air grille with 16x14 inch dimensions will require a 14x12 inch hole and a 16x14 inch frame.

If you fit into the ‘show, don’t tell’ school of thought, check out our video tutorial on how to size supply and return grilles correctly.


Why do your grilles need to be correctly sized?

Correctly sized supply and return air grilles promote optimum airflow throughout a home. If a grille is too large or fitted incorrectly, air movement is restricted and the louvers could be facing vertically — both of which put a strain on your HVAC system and affect temperature.

It’s a good rule of thumb to keep your louvers horizontal. This allows you to angle your adjustable grille toward the ceiling in summer, so cold air can fall naturally and cool the room. In winter, you can face the grille down so that the heat rises to warm the room. As your HVAC system can circulate the air evenly, with less effort, these practices are more energy-efficient and cost-effective in the long-run.

Return air grilles work best with fixed grilles, as the direction of the air does not matter. With supply grilles, you'll want an adjustable grille with louvers so that you can spread the air evenly throughout the room.


Still unsure on how to size supply and return air grilles?

It looks simple enough on paper, but we understand if you’re uncertain about how to get the perfect fit for your HVAC system.

That’s why we’re here.

With over 10 years of experience in the industry and more than 5 million satisfied customers, HVAC Premium can guarantee your grilles are perfectly fitted. We also have the largest selection in the USA, with all styles and sizes ready to ship.

Browse our high-quality range of supply and return air grilles. For expert advice and guidance, please get in touch with one of our consultants.


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