HOLLAND, MI — When looking at the big picture as it applies to a building’s HVAC system, the grilles, registers, and diffusers play a more important role than some contractors and technicians may realize.

That is why Hart & Cooley has been offering training to its suppliers and contractor customers — to make sure they are choosing the proper equipment for optimum air distribution and comfort.

Dave Fetters, technical service engineer for Hart & Cooley, travels all over the country in order to educate contractors on the company’s product line and how to choose the grille, register, or diffuser that is right for a specific job.

According to Fetters, this kind of information is often overlooked when new technicians are trained. He says that this process can be difficult for more seasoned contractors, especially for those who are taking on new jobs that are different from their traditional installations.


The goal of the training, according to Fetters, is to help contractors give consumers the comfort they need. But every consumer is different. This makes the process of selecting an adequate grille, register, or diffuser a bit more difficult.

A few environmental aspects contractors should keep in mind when choosing air distribution equipment include the type of room, activities that take place in the room, and the size of the area. With this in mind, a contractor must realize the proper air volume, air motion, ambient temperature, and system noise that is suitable for the particular space.

And although there are several things to keep in mind, Fetters says that the course helps present some basic characteristics that might be comfortable for a majority of people. It also helps contractors choose equipment for unique installations.

Fetters says that he first explains some of the basic principles of air distribution and how his company’s products work to help regulate airflow and keep rooms comfortable. By starting with basic principles, Fetters says that all the participants will be on the same page.

Fetters then tells contractors that selecting the proper equipment is not always clear cut.

“This is not 100% science,” he says. “We’re dealing with human comfort, and all humans are different.”


Fetters explains that choosing the right grille, register, and diffuser will have a lot to do with the needs of the physical space. He says installers must know how much air is needed in the particular environment and how far this air must be thrown.

With this in mind, it is very important for the contractors to become familiar with terms such as air velocity, throw, and drop. The placement of grilles and registers will determine how far the air will travel and how much area it will cover.

For example, Fetters says that installers must determine whether grilles and registers will be placed on the floor, at the baseboards, on the walls, or at the ceilings. This is important because of the air movement. Fetters explains that heat travels upwards, which means it would be more effective to distribute heated air from grilles closer to the floor. If the heat is distributed closer to the ceiling, the heat will hang higher in the air and will not heat a majority of the space. In heating applications, Fetters says return grilles should be placed on the ceiling to collect stagnant air.

For cooling, it is the exact opposite. Fetters suggests distributing cool air from a high sidewall or ceiling diffusers. The instructor also talks about upward jets to distribute cool air from the floor. Fetters does not suggest using this application to distribute heat for the same reason he does not suggest using ceiling diffusers for heating. He says that conditioned air is best introduced opposite of where it wants to flow naturally.


Fetters says that most of the participants in the course inquire about unique installations or environments they are not used to dealing with on a regular basis.

“Some contractors are used to dealing with single-family dwellings,” says Fetters. He explains that when a contractor is commissioned to work on such installations as churches or commercial buildings, the rules change somewhat.

Fetters says that the contractors know what to do, but they may need a little guidance to get it just right.

What makes some applications more challenging has to do with the amount of air movement required compared to the desired noise level. To be more specific, some building spaces require a higher CFM or a larger throw of air, but at the same time, the environment must be relatively quiet.

Churches, recording studios, libraries, and home offices are only a few examples. To deal with these situations, Fetters tells contractors to pay special attention to the NC criteria that will be listed for the product. NC levels between 25 and 30 are perfectly suited for spaces that cannot be disrupted by noise from diffusers and registers.

NC levels over 40 will generate more noise. But equipment with these higher NC ratings work well for such environments as warehouses, manufacturing facilities, and computer rooms.

Contractors must also take a look at the recommended velometer velocities. Industrial buildings, department stores, and general offices fall in the region of 1,500 to 2,000 FPM.

Quieter and sometimes smaller locations, such as churches, residences, apartments, and hotel bedrooms, are best suited for 500 to 750 FPM. Mid-range spaces can fall anywhere between 750 and 1,250 FPM.

Noise isn’t the only factor that can make an application a bit more challenging. Fetters says that some architects gear their building designs more towards style and can forget about including easy accommodations for heating and cooling. Examples include buildings with glassed-in entryways. These must be heated during winter without fogging up windows.

Another problem is posed by indoor swimming pools, where ventilation is required over distributing heating and cooling. Both of these applications require the contractor to take a more in-depth look at the amount of air that will be distributed, and what kind of equipment will help keep the areas comfortable.

After a contractor has realized the needs of the environment and the equipment that will provide these needs, Fetters says consumers sometimes throw a wrench in the plans. The cost and appearance of the equipment can be more important to a customer than proper ventilation and air distribution.

Fetters suggests that contractors explain their selection to the owner and tell him or her why it is more beneficial for their environment.

Each year, Fetters travels across the country introducing contractors to Hart & Cooley products and how they can eliminate a number of these installation problems.

For more information on training, ask your Hart & Cooley distributor or go to www.hartandcooley.com (website).

Publication date: 07/29/2002