Uneven Temperature Between Bonus Room and Rest of Home

I've got a question for you. I live in a two story home approximately 2400 Sq ft. with a bonus room above the garage. The heating/cooling equipment is located in the attic. In two weeks, I'm going to have the first and second stories split into separate HVAC zones.
An issue I'm facing is the bonus room is either warmer or cooler than the remainder of the house depending on the season. The HVAC tech suggested adding a 12x12 return duct in the bonus room; in addition to a previously existing duct in the upstairs hallway, to help equalize the temperature. I read the return ducts should equal the total size of the heating/cooling ducts in the rooms. So, if a second duct were added in the bonus room, would the existing return duct in the hallway need to be reduced accordingly?
Any information you can provide would be helpful. Secondary resources would also be beneficial.
Regards, Orlanzo
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It would help to know for sure you mean it is hotter in summer, cooler in winter. There have been complaints of the opposite.

You have to determine if the insulation is correct too, fix if necessary. YOud on['t have to reduce the duct size, but you can try blocking off a portion of the return to see if that makes a difference. If it does, j ust put a beffle as needed.

"There is something called Manual J to determine the size AC you need, and a manual D to determine the duct size. That should be done before you put in the dual system. It may save a lot of money to do the job right.
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Edwin,
I appreciate the response...
The rooom is warmer than the rest of the house in the summer. The opposite is true in the winter months. The insulation did pass inspection when it was installed two years ago. Although, I did read some information that suggested some additional improvements that would help rooms above the garages ro carports. And, I understand a baffle could be used to help balance the returns.
Thanks also for the references you provided. All of this helps ensure I'm doing the right thing for my situation.

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I would NEVER reduce return duct size to any room where I wanted AC.
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He isn't. He is adding to the room he wants more air and trying to balance the system. While the return cannot actually move more air that is supplied to it, you can vary openings to push more to another area though.
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ok I'm in the same boat you are. we have 2400sq home and its 1 level. the 2 cargarage was turned into a gaint bedroom 400sqfoot room years ago and we are still plagued by the cooling and heating problem.in the summer its too hot and winter ice cold. the problem is the run of the pipes. just too long. we got a hvac guy to install 2 ceiling outlets for the system. and a duct return.
the problem we are having now is if we leave the garage door open to the rest of the house in summer ,hot air comes into the rest of house and causes the a/c to run constant. same for winter.
you might want to ask about a inline duct fan that will pull more hot/ cold air in when the unit switch on for the season. they pretty cheap less than 100.00 and all you do is hook them up to the furnace electrical.
make sure you have a aquate heating and cooling system for it.
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On Jul 19, 7:08 pm, snipped-for-privacy@gmail.com wrote:

Thanks for the information...
In my case, the unit HVAC unit is in the attic. It's probably less than 20 feet from the bonus room. But, the actual duct runs (from the main upstairs distribution box to two outlets) to the room may be greater. Adding a duct fan may be beneficial. I'll raise the question with the company doing the installation work.
I'm definitely going to separate the heating and cooling for the upper and lower levels into distinct zones. The duct fan could be a more appropriate and cheaper alternative in the bonus room. Did that alleviate the problem in your home? Or, are you still having the issue; even though, you've installed additiona outlets and a return duct in the room.
Thank you for your response!
Orlanzo
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