An HVAC diffuser allows you to distribute treated air more effectively in any location. A diffuser is a device, usually round though it can be a rectangle, that is installed on an air duct. Its purpose is to push air out of it in a 360-degree arc, forcing into the room evenly.
Diffusers are used with either AC-only systems or with heating/cooling systems. They can also be used to distribute ventilation air into any space.
HVAC diffusers are almost always installed in the ceiling. The reason for this is that cold air falls. Plus, their construction allows air to be distributed most evenly over a large area. If you’ve been in a store or restaurant with a warehouse-type open ceiling, you might have noticed large diffusers attached to the ductwork running along the ceiling. Commercial diffusers of that type can be 18”-36” wide.
For residential use, HVAC diffusers are more typically 6”-12” in diameter. The size is consistent with the size and airflow capacity of the duct work they are used with.
Diffusers are often found in living space with open architect, such as apartment flats made from converted commercial buildings and popular in urban areas. They are also a typical feature in basements because the duct work is almost always overhead. They are attached to vertical, often round, duct runs.
HVAC diffusers are made from metal, the same type of sheet metal used in duct work. They have 2-4 separate rings. Each ring is angled slightly differently.
The purpose of the different angles is to distribute – literally to diffuse – the air at different angles. The outermost ring is the flattest, so air going through it goes out more horizontally, reaching more distant parts of the room. As the rings move toward the center, they are angled more downward. The result is concentric cones of air being forced into the room for even coverage.
For cooling, diffusers work very well since cooled air will settle downward into a room. They are less efficient with heated air because of the ceiling installation and the tendency of hot air to rise. When used in commercial applications and in some residential settings, a ceiling fan is often installed to better circulate air downward.
Sometimes dampers are installed with the diffuser in order to restrict airflow through it. For example, since basements are submerged underground and naturally cool, some homeowners don’t air condition them but do like to heat the basement. The damper can be used to close the diffuser in the summer and open it in the winter to allow for heating. This can sometimes lead to noise however, as the damper might vibrate with passing air.
Consult a qualified contractor to determine whether the use of HVAC diffusers is a good choice for your home, apartment or commercial building, and how installing one will affect HVAC prices. The HVAC professional will design a duct work system that will most evenly distribute heating and/or cooled air throughout the space you want to treat.