Diffuser placement

[jgcool]

We have added a 25' x 25' great room with 24 high cathedral ceilings. At what height should the vents be placed for cooling purposes only?

[jgcool]

how high should the cooling vents be placed to cool a 25' x 25' room with 24' high cathedral ceilings?

[second opinion]

That is not going to be an easy question without knowing more information. Depending on registers or difusers. Window locations. Velocity of the air,throw, and spread of the terminals that you chose. You want the airflow to be within the occupied zone. Two feet in from the walls and floor to 6 feet.

[Gib's Son]

For cooling only....who care how high they are. The cold air will work it's way down no mater what. Heating on the other hand is entirely different. You need enough velocity to break through the thermalcline. The hotter the air, the harder it will be.

[jgcool]

We are taking about registers here and it is only used for cooling. The room will have radiant heat so no HVAC for heating unless we have an emergency and need to use the heat pump.
The room is in the middle of the house and the only external wall faces east. This outside wall has a firplace with windows and outswinging Frech doors on both side of the fireplace. The walls around the room are about 10' high and then the roof rafters go up at 45degrees. The insulation in the rafters is R30C. The back part of the room is open to the rest of the house so it is a very large open floor plan.
Tks for the reponse so far.

[wahoo]

You only need to cool just above your head, so raising the discharge registers higher than that will only increase your actual space cooled. You need to look into the "throw" of each type of register at a given air velocity. Your HVAC person should be able to coordinate with you about what register works best. NEVER put round registers up into a 24 ft. high ceiling as the cooling will never reach the floor and if it did, your actual cooling load would be way too high. I assume you have large windows in the east wall? Your HVAC person would need to add the solar load of these windows when sizing the registers and ductwork feeding them.:.02: