One room cool and other oom not that much cool

bought a new house in Allen, Tx and during the last couple of months in the summer I noticed that the room above the garage gets very cold where as the media room next to it does not get that cold. Media room is a bigger room and is insulated on 3 sides as per the builder. I run the projector only once or twice a week for about 5 hrs to see couple of movies. Other than that nothing is running in the media room. All the other rooms upstairs are fine.
I had the builder look at it and they suggested that I keep the vent closed a notch in the room above the garage. That did not help. He checked all the vents and he said everything is fine as per the blue print. I am not getting a satifactory answer. What could be wrong and what are the possible solutions to fix the issue.
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On Oct 22, 10:49 pm, snipped-for-privacy@yahoo.com wrote:

Lots of things could be wrong. They could have not provided enough duct capacity to the media room. Or it could have no returns. Or a duct could have been improperly installed, wrapped with a little bit of tape, come loose and is disconnected. My guess would be that the media room is at the farthest end of the run.
Do an inspection of the ducts and returns in that area. Find out which other rooms feed off the same duct route. Then close registers on rooms that are cooler on the same path and make sure everything is open in the media room. What volume of air is coming out of there now? It should increase when you close off some of the other registers on the same ducting.
Check the attic venting and insulation. Is the attic well vented with soffit vents and hopefully a ridge vent? Is insulation in place and also not blocking the soffit vents? Placing a radiant foil barrier against the rafters can also help.
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Try two notches, or three notches. Be sure the return vent in the warmer room is not blocked.
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